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Synthetic Development of Heterocyclic Based Extractants for the Selective Recognition and Separation of f-Elements in Bi...

Permanent Link: http://ufdc.ufl.edu/UFE0042523/00001

Material Information

Title: Synthetic Development of Heterocyclic Based Extractants for the Selective Recognition and Separation of f-Elements in Biphasic Systems
Physical Description: 1 online resource (168 p.)
Language: english
Creator: Guillet, Gary
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: actinides, lanthanides, triphenoxymethane
Chemistry -- Dissertations, Academic -- UF
Genre: Chemistry thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy SYNTHETIC DEVEOLOPMENT OF HETEROCYCLIC BASED EXTRACTANTS FOR THE SELECTIVE RECOGNITION AND SEPARATION OF f-ELEMENTS IN BIPHASIC SYSTEMS By Gary L. Guillet December 2010 Chair: Michael J. Scott Major: Chemistry Three new families of green extractants have been synthesized separated by the donor set. They are based off of pyridine-picolinamide, (1,2,4-triazin-3-yl)-picolinamide, and 1,2,4-triazine-pyridine-triazole and they have been synthesized from simple starting materials in high yield and purity. All ligands are nonadentate based off of the triphenoxymethane platform. The target ligands extraction behavior was examined towards a select group of lanthanides. Extractions were performed with metal to ligand ratios of 10:1 from 1M nitric acid aqueous phases into either dichloromethane or 1-octanol. Each of the ligand sets showed limited ability to extract lanthanides with (1,2,4-triazin-3-yl)-picolinamide showing a modest selectivity for the smaller, heavier lanthanides (Dy-Yb) over the larger lanthanides. The solid-state structure of ligands with different lanthanides was explored to probe the effect of changing metal radius on the binding pocket and the congruence to ideal trigonal tricapped prismatic geometry. The alkyl substitution on the triphenoxymethane platform was also modulated to determine the effect of steric hindrance on coordination and extraction. A correlation was found between the extraction efficiency and the ability of the ligand to meet the ideal trigonal tricapped prismatic geometry that is seen by lanthanides and actinides in aqueous solution. The binding constants were examined using UV/VIS spectroscopy. The largest binding constants correlated moderately well with ligand metal combinations that showed the greatest extraction extent. The kinetics of metallation was also explored using UV/VIS spectroscopy with pseudo first order conditions and showed similar behavior to literature examples. Theoretical calculations were performed to analyze the bond character as actinides are known to have an increased covalent contribution in their bonding that the lanthanides do not show. Literature ligands that are known selective extractants for actinides over lanthanides were initially examined to validate the theoretical approach. The defined methods were then applied to synthesized ligands to determine if any congruence existed. Development of a method to predict ligand properties towards preference for actinide coordination and extraction is a work in progress.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Gary Guillet.
Thesis: Thesis (Ph.D.)--University of Florida, 2010.
Local: Adviser: Scott, Michael J.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0042523:00001

Permanent Link: http://ufdc.ufl.edu/UFE0042523/00001

Material Information

Title: Synthetic Development of Heterocyclic Based Extractants for the Selective Recognition and Separation of f-Elements in Biphasic Systems
Physical Description: 1 online resource (168 p.)
Language: english
Creator: Guillet, Gary
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: actinides, lanthanides, triphenoxymethane
Chemistry -- Dissertations, Academic -- UF
Genre: Chemistry thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy SYNTHETIC DEVEOLOPMENT OF HETEROCYCLIC BASED EXTRACTANTS FOR THE SELECTIVE RECOGNITION AND SEPARATION OF f-ELEMENTS IN BIPHASIC SYSTEMS By Gary L. Guillet December 2010 Chair: Michael J. Scott Major: Chemistry Three new families of green extractants have been synthesized separated by the donor set. They are based off of pyridine-picolinamide, (1,2,4-triazin-3-yl)-picolinamide, and 1,2,4-triazine-pyridine-triazole and they have been synthesized from simple starting materials in high yield and purity. All ligands are nonadentate based off of the triphenoxymethane platform. The target ligands extraction behavior was examined towards a select group of lanthanides. Extractions were performed with metal to ligand ratios of 10:1 from 1M nitric acid aqueous phases into either dichloromethane or 1-octanol. Each of the ligand sets showed limited ability to extract lanthanides with (1,2,4-triazin-3-yl)-picolinamide showing a modest selectivity for the smaller, heavier lanthanides (Dy-Yb) over the larger lanthanides. The solid-state structure of ligands with different lanthanides was explored to probe the effect of changing metal radius on the binding pocket and the congruence to ideal trigonal tricapped prismatic geometry. The alkyl substitution on the triphenoxymethane platform was also modulated to determine the effect of steric hindrance on coordination and extraction. A correlation was found between the extraction efficiency and the ability of the ligand to meet the ideal trigonal tricapped prismatic geometry that is seen by lanthanides and actinides in aqueous solution. The binding constants were examined using UV/VIS spectroscopy. The largest binding constants correlated moderately well with ligand metal combinations that showed the greatest extraction extent. The kinetics of metallation was also explored using UV/VIS spectroscopy with pseudo first order conditions and showed similar behavior to literature examples. Theoretical calculations were performed to analyze the bond character as actinides are known to have an increased covalent contribution in their bonding that the lanthanides do not show. Literature ligands that are known selective extractants for actinides over lanthanides were initially examined to validate the theoretical approach. The defined methods were then applied to synthesized ligands to determine if any congruence existed. Development of a method to predict ligand properties towards preference for actinide coordination and extraction is a work in progress.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Gary Guillet.
Thesis: Thesis (Ph.D.)--University of Florida, 2010.
Local: Adviser: Scott, Michael J.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0042523:00001


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1 SYNTHETIC DEVE LOPMENT OF HETEROCYCLIC BASED EXTRACTANTS FOR TH E SELECTIVE RECOGNITION AND SEPA RATION OF f ELEMENTS IN BIPHASIC SYSTEMS By GARY L. GUILLET A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2010

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2 2010 Gary L. Guillet

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3 To my mother, father brother and sister who have always support ed always trust ed and always believe d in me

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4 ACKNOWLEDGMENTS First off, I want to acknowledge the commitment and love my mother and father have committed to me throughout my life and their steady support through thick and thin. They have always put me in positions to make decisions for myself equipped with the experience to meet them. The example they set throughout my life with their ethic, their integrity, and their commitment to hard work set the tone for my approach to every challenge I have met Many individuals ha ve steered me towards bigger goals and greater achievement Dr. Kathryn Williams was a great voice of encouragement and I want to thank her for the guidance that I received during my tenure as an undergraduate and as a gra duate student at the Univ ersity of Florida. My decision to enter the Ph.D. program at UF was a direct result of her prompting of me and her belief that I was the caliber of student that could be successful even at times Sh e is someone who impacted my approach to research and to educating. I respect and admire her as an educator and also as a friend. Two undergraduates who deserve recognition were Michael Pawley and Jeremy Brenner. They both put great effort into their wor k and they also have the second task of dealing with me as I learned how to guide their research. Their patience and commitment to the research are much appreciated. I would also like to thank my outstanding peers whom I worked with during my time at UF. First of all I need to thank Patrick Hillesheim and Dempsey Hyatt who over the years we worked together were great co workers but became better friends I leaned on them more than once when the pressure of the program became

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5 overwhelming and the camarade rie that was born out of those situations was indispensible While I had the blessing of being friends with many of my peers in other research groups throughout the department two deserve special recognition. Soumya Sa r kar and Shreya Mukherjee were a con stant in my daily laboratory life and they were always a positive influence at times to help me focus on my chemistry and at other times when I need ed to change my focus Handling the difficulties and challenges in research is a s daunting when you can look back on the time with so many fond memories of time with people who are special to you. I would finally like to thank my advisor Dr. Michael J. Scott The direction and effort he put into my career were beneficial for my gro wth as a scientist I am thankful for the opportunity to work in his lab where I was allowed the freedom to pursue my ideas at all times.

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6 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ .. 4 LIST OF TABLES ................................ ................................ ................................ .......... 10 LIST OF FIGURES ................................ ................................ ................................ ........ 11 ABSTRACT ................................ ................................ ................................ ................... 15 CHAPTER 1 INTRODUCTION ................................ ................................ ................................ .... 17 1 1 Nuclear Power Overview ................................ ................................ .................. 17 1 2 Constituents in Spent Nuclear Fuel ................................ ................................ .. 18 1 3 Nuclear Waste Treatment Strategies ................................ ................................ 19 1 3.1 Transmutation ................................ ................................ ......................... 20 1 3.2 Recycling and Treatment Strategie s Currently In Use ............................. 20 1 3.2A P lutonium UR anium EX traction (PUREX) ................................ ...... 21 1 3.2B DIA mide EX traction (DIAMEX) ................................ ....................... 21 1 3.2C S elective A cti N ide EX traction (SANEX) ................................ ......... 21 1 4 Properties comparison of 4f and 5f Elements ................................ ................... 22 1 5 Experimental Evidence for Covalency in the Bonding of An Complexes .......... 24 1 6 Theoretical Approaches to Elucidation of Ligand Selectivity ............................. 25 1 7 Preorganization of Donors and the Chelate Effect ................................ ............ 26 1 8 Research Objectives ................................ ................................ ......................... 28 2 BIPYRIDINE BASED EXTRACTANTS TETHE RED TO THE TRIPHENOXYMETHANE PLATFORM SYNTHESIS AND EXTRACTION PROPERTIES ................................ ................................ ................................ ......... 34 2 1 Introduction ................................ ................................ ................................ ....... 34 2 2 Results and Discussion ................................ ................................ .................... 35 2 2.1 Synthesis of Target Ligands ................................ ................................ .... 35 2 2.2 Solid State Structure of Eu(2 6 c ) 3+ ................................ .......................... 36 2 2.3 Binding Constant Studies ................................ ................................ ........ 36 2 2.4 Biphasic Extraction Studies ................................ ................................ ..... 38 2 2.4A Solubility issues ................................ ................................ .............. 38 2 2.4B Reproducible extraction results ................................ ...................... 39 2 3 Conclusions ................................ ................................ ................................ ...... 41 2 4 Experimental ................................ ................................ ................................ ..... 42 2 4.1 General Considerations ................................ ................................ ........... 42 2 4.2 Binding Constant UV/VIS Measurements ................................ ................ 42 2 4.3 Metal Extraction Experiments ................................ ................................ .. 43 2 4.4 Synthetic Procedures ................................ ................................ .............. 44

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7 2 4.4A Compound 2 4 ................................ ................................ ................ 44 2 4.4B Compound 2 5 ................................ ................................ ................ 45 2 4.4C Compound 2 6 a ................................ ................................ .............. 45 2 4.4D Compound 2 6 b ................................ ................................ .............. 46 2 4.4E Compound 2 6 c ................................ ................................ .............. 47 2 4.4F Compound Eu(2 6 c )(SO 3 CF 3 ) ................................ ......................... 48 2 4.5 X Ray Structure Solution ................................ ................................ ......... 48 3 BIS (1,2,4 TRIAZIN 3 YL) PYRIDINE EXTRACTANTS TETHERED TO THE TRIPHENOXYMETHANE PLATFORM SYNTHESIS AND EXTRACTION PROPERTIES ................................ ................................ ................................ ......... 56 3 1 Introduction ................................ ................................ ................................ ....... 56 3 1.1 Evidence of Bis (1,2,4 triazine)Pyridine selectivity ................................ .. 56 3 1.2 Radiolytic and Hydrolytic Degradations of N Donor Extractants ............. 57 3 1.2A Degradation of BTP ................................ ................................ ........ 57 3 1.2B Degradation of BTBP ................................ ................................ ...... 58 3 2 Results and Discussion ................................ ................................ .................... 58 3 2.1 2,6 Bis 1,2,4 Triazin 3 yl Pyridine Based Extractants ............................. 58 3 2.2 6 (5,6 diphenyl 1,2,4 Triazine 3 yl)Picolina mide Based Extractants ....... 59 3 2.2A Synthesis of (5,6 Diphenyl 1,2,4 triazin 3 yl) picolinamide ligands incorporating the triphenoxymethane platform ........................... 60 3 2.2B Hydrolytic degradation investigation ................................ ............... 61 3 2.2C Solid State structure comparison of ML and ML 3 complexes with La, Eu, Er, and Yb ................................ ................................ .................. 61 3 2.2D Metallation rate studies ................................ ................................ .. 64 3 2.2E Binding constant studies ................................ ................................ 65 3 2.2F Extraction efficiency studies ................................ ........................... 66 3 2.3 6 (5,6 diphenyl 1,2,4 triazin 3 yl)diisobutyl Picolinamide Analogue ........ 67 3 3 Conclusions ................................ ................................ ................................ ...... 68 3 4 Experimental ................................ ................................ ................................ ..... 7 0 3 4.1 General Considerations ................................ ................................ ........... 70 3 4.2 Binding Constant and Kinetics UV/VIS Experiment al Conditions ............ 70 3 4.3 Metal Extraction Experiments ................................ ................................ .. 71 3 4.4 Synthetic Procedures ................................ ................................ .............. 72 3 4.4A Compound 3 7a ................................ ................................ .............. 72 3 4.4B Compound 3 9 ................................ ................................ ................ 73 3 4.4C Compound 3 10 ................................ ................................ ............. 73 3 4.4D Compound 3 11 ................................ ................................ ............. 74 3 4.4E Compound 3 12 ................................ ................................ .............. 74 3 4.4F Compound 3 15 ................................ ................................ .............. 75 3 4.4G Compound 3 16 ................................ ................................ ............. 76 3 4.4H Compound 3 17 ................................ ................................ ............. 77 3 4.4I Compound 3 18 ................................ ................................ ............... 78 3 4.4J Compound 3 19 ................................ ................................ .............. 79 3 4.5 General Procedure for Metal Complex Synthesis ................................ ... 80 3 4.5A Yb(3 7 a ) 3 (NO 3 ) 3 ................................ ................................ .............. 80

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8 3 4.5B Yb(3 7 b ) 3 (SO 3 CF 3 ) 3 (CH 3 OH) 3 ................................ ......................... 80 3 4.5C La 2 (3 17)(NO 3 ) 6 (CH 3 OH) 6 ((H 3 CH 2 C) 2 O) 3 ................................ ...... 80 3 4.5D Er 2 (3 17)(NO 3 ) 6 (CH 3 OH) 6 ((H 3 CH 2 C) 2 O) 2 ................................ ....... 81 3 4.5E Yb 2 (3 17)(NO 3 ) 6 (CH 3 OH) 6 ((H 3 CH 2 C) 2 O) ................................ ....... 81 3 4.5F Yb(3 18)(NO 3 ) 3 (CH 3 OH) 3 ................................ ............................... 81 3 4.5G Yb(3 19)(SO 3 CF 3 ) 3 ................................ ................................ ......... 82 3 4.5H Yb(3 16) 3 (SO 3 CF 3 ) 3 ................................ ................................ ........ 82 3 4.5I Eu 2 (3 18)(NO 3 ) 6 (CH 3 OH) 3 ................................ ............................... 83 3 4.6 X Ray Structure Solution ................................ ................................ ......... 83 4 TRIAZZOLE BASED LIGANDS AS PREORGANIZED MIMICS OF BIS (1,2,4 TRIAZIN 3 YL) PYRIDINES SYNTHESIS AND EXTRACTION PROPERTIES ... 97 4 1 Introduction ................................ ................................ ................................ ....... 97 4 2 Results and Discussion ................................ ................................ .................... 98 4 2.1 Ligands synthesis ................................ ................................ .................... 98 4 2.2 Solid State Structure ................................ ................................ ............... 99 4 2.3 Binding Constant Studies ................................ ................................ ...... 100 4 2.4 Extractions ................................ ................................ ............................ 100 4 3 Conclusions ................................ ................................ ................................ .... 101 4 4 Experimental ................................ ................................ ................................ ... 103 4 4.1 General Considerations ................................ ................................ ......... 103 4 4.2 Binding Constant UV /VIS Measurements ................................ .............. 103 4 4.3 Synthetic Procedures ................................ ................................ ............ 104 4 4.3A Compound 4 4 ................................ ................................ .............. 104 4 4.3B Compound 4 5 ................................ ................................ .............. 104 4 4.3C Compound 4 6 ................................ ................................ ............. 105 4 4.3D Compound 4 7 ................................ ................................ ............. 106 4 4.3E Compound 4 9 ................................ ................................ .............. 106 4 4.3F Compound Yb 2 (4 9)(NO 3 ) 6 (CH 3 OH) 6 ((CH 3 ) 3 COCH 3 ) 2 .................. 107 4 4.4 X Ray Structure Solution ................................ ................................ ....... 107 5 THEORETICAL COMPARISON OF BIS (1,2,4 TRIAZIN 3 YL)PYRIDINES WITH ANALOGUES OF EXTRACTANTS FOR THE SEGREGATION OF LANTHANIDES AND ACTINIDES ................................ ................................ ........ 113 5 1 Introduction ................................ ................................ ................................ ..... 113 5 2 Results and Discussion ................................ ................................ .................. 115 5 2.1 Geometry Optimizations ................................ ................................ ........ 115 5 2.2 Ligand Orbital Comparison ................................ ................................ .... 116 5 2.3 ML 3 3+ Electronic Structure ................................ ................................ ..... 117 5 2.3A Molecular Orbital Visualization s ................................ ................... 118 5 2.3B Bis 1,2,4 triazin 3 yl pyridine Molecular Orbital Descriptions ....... 120 5 2.3C (1,2,4 Triazin 3 yl)Picolinamide ................................ .................... 122 5 2.3D (1,2,4 Triazin 3 yl)(1,2,3 Triazol 4 yl)Pyridine .............................. 124 5 2.3E Pyridine Picolinamide ................................ ................................ ... 125 5 3 Conclusions ................................ ................................ ................................ .... 126

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9 5 4 Computational Details ................................ ................................ ..................... 128 APPENDIX; 1 H NMR AND 13 C NMR SPECTRA ................................ ......................... 134 LIST OF REFERENCES ................................ ................................ ............................. 161 BIOGRAPHICAL SKETCH ................................ ................................ .......................... 168

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10 LIST OF TABLES Table page 1 1 Masses of long lived radionuclides from 1 tonne of SNF. 6 ................................ .. 32 1 2 Relatively accessible oxidations states of the Ln and An. 18 ................................ 33 1 3 Extraction percent for preorganized CMPO ligands from 1M nitric acid aqueous solution into NPHE. 35 ................................ ................................ ........... 33 2 1 Binding constant data for complexes of 2 6 b with La, Eu, and Yb. All values refer to 1:1 complexes. ................................ ................................ ....................... 55 3 1 Comparison of La(3 17)(NO 3 ) 3 Er(3 17)(NO 3 ) 3 and Yb(3 17)(NO 3 ) 3 solid state structures. ................................ ................................ ................................ .. 93 3 2 Solid structure comparison of Yb(3 17)(NO 3 ) 3 Yb(3 18)(NO 3 ) 3 and Yb(3 19)(SO 3 CF 3 ) 3 ................................ ................................ ................................ ..... 94 3 3 Comparison of terdentate ligands in Yb(L) 3 3+ complexes to Yb(3 17)(NO 3 ) 3 ..... 94 3 4 Experimentally determined k obs and k for 3 19 with Yb(NO 3 ) 3 in acetonitrile. ...... 94 3 5 Binding constants for 3 19 in acetonitrile for the metall ation reaction M 3+ + L ML 3+ ................................ ................................ ................................ .............. 94 3 6 X ray data for reported crystal structures of nonadentate (3 17, 3 18, 3 19) and terdentate (3 7 a 3 7 b, 3 16) metal complexes. ................................ ............. 95 4 1 Bond lengths and prism twist angle in Yb(4 9) 3+ with Yb(3 19) 3+ included for comparison. ................................ ................................ ................................ ...... 111 4 2 Measured binding constants for 4 9 in acetonitrile. The [L] was approxim ately 2 x 10 5 M. ................................ ................................ .................. 111 4 3 X ray crystal data for the solid state structure of Yb 2 (4 9)(NO 3 ) 6 ..................... 112 5 1 Bond length comparison of e xperimental solid state structure data and literature values. ................................ ................................ ............................... 132 5 2 Comparison of theoretical calculation results to literature calculation and experimental results for M(5 1) 3 3+ complexes. ................................ ................. 132 5 3 Complete geometry optimization results for all M(5 1) 3 3+ M(5 3) 3 3+ M(5 4) 3 3+ and M(5 5) 3 3+ complexes. ................................ ................................ ................. 133 5 4 HOMO L UMO gap for L 3 fragments (5 1) 3 (5 3) 3 (5 4) 3 and (5 5) 3 ............. 133

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11 LIST OF FIGURES Figure page 1 1 Total Number of U.S. Nuclear Power Plants from 1960 t o 2008. ........................ 29 1 2 Constituents of Spent Nuclear Fuel assemblies upon retirement. 5 ..................... 29 1 3 Schematic of common spent fuel processing techniques ................................ ... 30 1 4 Representative examples of extractants used in recycling processes. ............... 30 1 5 Bis triazinyl pyridine (BTP) used i n SANEX process as alternative to DTPA. .... 30 1 6 Comparison of Ln(III) and An(III) ionic radii all with C.N. = 6 Data for Th only available for Th 4+ 38 ................................ ................................ ............................. 31 1 7 An ligands compared to determine covalent bonding effect on bonding and structure. ................................ ................................ ................................ ............ 31 1 8 Sample of common preorganized scaffolds used in preorganization of donor groups. ................................ ................................ ................................ ............... 31 1 9 Extractants used for comparison of preorganization effect with the CMPO donor set towards Eu and Am ................................ ................................ ........... 32 1 10 Extracted species for Am by CMPO from an acidic aqueous phase into an organic phase. 36 ................................ ................................ ................................ 32 2 1 Example structure of heptadentate bipyridine complex coo rdinated to UCl 2 41 ... 49 2 2 Bis (5,6 dialkyl 1,2,4 triazin 3 yl) bipyridine (BTBP) ........ 49 2 3 Distribution ra tio of preorganized D GA triphenoxymethane derivative and terdentate DGA. ................................ ................................ ................................ .. 50 2 4 Synthetic scheme for 6 carboxy bipyridine. 49 ................................ .............. 50 2 5 Triphenoxymethane scaffolds used for preorganization of donor groups. .......... 50 2 6 Synthetic schemes for nonadentate bipyridine ligands. ................................ ...... 51 2 7 Solid state structure of Eu(2 6 c )(SO 3 CF 3 ) 3 ................................ ........................ 51 2 8 Representative plot of spectra from titration of 2 6 b with Yb(NO 3 ) 3 in acetonitrile. ([L] approx. 2 x 10 5 M) ................................ ................................ .... 52 2 9 Ligands used in binding constant comparison. ................................ ................... 52

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12 2 10 Extraction results for 2 5 from 1M nitric acid into dichloromethane. ................... 53 2 11 Comparison of 1 H NMR spectra in CDCl 3 for 2 6a and a crystal grown in contact with a 1M HNO 3 aqueous phase ................................ ........................... 53 2 12 Extraction data for 2 6a (triangles), 2 6b (diamonds), and 2 6c (squares) from 1M nitric acid into dichloromethane ................................ ................................ .... 54 2 13 Extraction data for 2 6a (triangles), 2 6b (diamonds), 2 6c (squares), and 2 9 (circles) ................................ ................................ ................................ .............. 54 2 14 Results comparing extraction with 2 6 b with COSAN (diamonds) and without (squares) ................................ ................................ ................................ ........... 55 3 1 Common organic terdentate N donor li gands found in the literature .................. 84 3 2 Description of the position susceptible to attack in extraction experiments with actinides. 72, 74 ................................ ................................ .............................. 84 3 3 BTP derivatives incorporating annulated rings for increased robustness. .......... 84 3 4 Proposed synthetic scheme for synthesis of tris BTP extractant. ....................... 85 3 5 Proposed ligand synthesis of target picolinamide extractant. ............................. 86 3 6 Synthesis of 6 (5,6 diphenyl 1,2,4 triazin 3 yl)picolinic acid and attempted synthesis of diethyl derivative ................................ ................................ ............. 86 3 7 Synthesized extractants containing the 1,2,4 triazinyl picolinamide moiety ....... 87 3 8 1 H NMR co mparison of ligand 3 19 before and after a 24 hour contact with 1M HNO 3 with the ligand in CD 2 Cl 2 ................................ ................................ .... 88 3 9 Represe ntative solid state structure shown here by La 2 (3 17)(NO 3 ) 6 ................. 89 3 10 Depiction of binding cavity surrounding M to highlight the distortion from ideal trigonal tricapped prismatic geometry. ................................ ................................ 90 3 11 Representative plot of UV/VIS spectra for titration of 3 19 with a 50:1 excess o f Yb ................................ ................................ ................................ ................... 90 3 12 Plot of ln(A A t ) versus time from which the k obs was extracted as the slope. .... 91 3 13 Representative plot of spectrum from titration of 3 19 with Yb(NO 3 ) 3 in acetonitrile ................................ ................................ ................................ ......... 91 3 14 Extraction efficiency for 3 7 a 3 16 3 17 3 18 and 3 19 ................................ ... 92

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13 3 15 Comparison of extraction res ults for 3 19 with COSAN added and without COSAN ................................ ................................ ................................ .............. 92 3 16 1 H NMR ( d acetone) analysis of solutio n structure of tedentate 3 16 ................. 93 4 1 Synthetic scheme for ligand arm 4 7 ................................ ............................... 108 4 2 Synthesis of the triazole based triphenoxymethane ligand 4 9. i) CuI, THF, 12hrs, r.t. ................................ ................................ ................................ .......... 109 4 3 Solid state structure of Yb(4 9) 3+ and b inding pocket ................................ ....... 109 4 4 Representative spectrum from titration of 4 9 with Yb(NO 3 ) 3 in acetonitrile. ... 110 4 5 Extraction results from 1M nitric acid into dichloromethane for 3 19 and 4 9 ... 110 5 1 Structures used as simplified analogues of synthesized structures .................. 128 5 2 Visua l representation of the HOMO[ 10] (left) and the HOMO[0] (right) of Am(5 1) 3 3+ ................................ ................................ ................................ ....... 129 5 3 Am(5 1) 3 3+ depicting interaction between the ligand HOFO[ 3] and Am f orbital (HOFO[ 2]) ................................ ................................ ............................ 129 5 4 Am(5 1) 3 3+ HOMO[ 10] as viewed down the z axis highlighting the bonding interaction. ................................ ................................ ................................ ........ 130 5 5 Cm(5 1) 3 3+ HOMO[ 33], HOMO[ 43], and HOMO[ 44] visualization highlighting the bonding interactions. ................................ ............................... 130 5 6 Cm(5 6) 3 3+ HOMO[ 24] and HOMO[ 30] ................................ .......................... 131 5 7 Bonding interactions between ligand molecul ar orbitals and Cm f orbitals ...... 131 5 8 Depiction of the HOMO[ 27] and HOMO[ 29] for Cm(5 3) 3 3+ ........................... 132 A 1 1 H NMR and 13 C NMR for Compound 2 4. ................................ ....................... 134 A 2 1 H NMR and 13 C NMR for Compound 2 5. ................................ ....................... 135 A 3 1 H NMR and 13 C NMR for Compound 2 6 a ................................ ...................... 136 A 4 1 H NMR and 13 C NMR for Compound 2 6 b ................................ ...................... 137 A 5 1 H NMR and 13 C NMR for Compound 2 6 c ................................ ...................... 138 A 6 1 H NMR and 13 C NMR for Compound 3 7 a ................................ ...................... 139 A 7 1 H NMR for Compound 3 7 b ................................ ................................ ............ 140

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14 A 8 1 H NMR and 13 C NMR for Compound 3 9. ................................ ....................... 141 A 9 1 H NMR and 13 C NMR for Compound 3 10. ................................ ..................... 142 A 10 1 H NMR and 13 C NMR for Compound 3 11. ................................ ..................... 143 A 11 1 H NMR and 13 C NMR for Compound 3 12. ................................ ..................... 144 A 12 1 H NMR for Compound 3 13. ................................ ................................ ........... 145 A 13 1 H NMR an d 13 C NMR for Compound 3 15. ................................ ..................... 146 A 14 1 H NMR and 13 C NMR for Compound 3 16. ................................ ..................... 147 A 15 1 H NMR and 13 C NMR for Compound 3 17. ................................ ..................... 148 A 16 1 H NMR and 13 C NMR for Compound 3 18. ................................ ..................... 149 A 17 1 H NMR and 13 C NMR for Compound 3 19. ................................ ..................... 150 A 18 1 H NMR for Compound La(3 17). ................................ ................................ ..... 151 A 19 1 H NMR for Compound Er(3 17). ................................ ................................ ..... 151 A 20 1 H NMR fo r Compound Yb(3 17). ................................ ................................ ..... 152 A 21 1 H NMR for Compound Yb(3 18). ................................ ................................ ..... 152 A 22 1 H NMR for Compound Yb(3 19). ................................ ................................ ..... 153 A 23 1 H NMR for Compound Yb(3 16) 3 ................................ ................................ ... 153 A 24 1 H NMR for Compound Yb(3 7 a ) 3 ................................ ................................ .... 154 A 25 1 H NMR for Compound Yb(3 7 b ) 3 ................................ ................................ .... 154 A 26 1 H NMR for Compound Eu(3 18). ................................ ................................ ..... 155 A 27 1 H NMR for Compound 4 4. ................................ ................................ ............. 155 A 28 1 H NMR and 13 C NMR for Compound 4 5. ................................ ....................... 156 A 29 1 H NMR and 13 C NMR for Compound 4 6. ................................ ....................... 157 A 30 1 H NMR and 13 C NMR for Compound 4 7. ................................ ....................... 158 A 31 1 H NMR and 13 C NMR for Compound 4 9. ................................ ....................... 159 A 32 1 H NMR for Comp ound Yb(4 9). ................................ ................................ ....... 160

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15 Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy SYNTHETIC DEVELOP MENT OF HETEROCYCLIC BASED EXTRACTANTS FOR TH E SELECTIVE RECOGNITION AND SEPA RATION OF f ELEMENTS IN BIPHASIC SYSTEMS By Gary L. Guillet December 2010 Chair: Michael J. Scott Major: Chemistry Three new families o f green extractants have been synthesize d separated by the donor set They are based off of pyridine picolinamide, (1,2,4 triazin 3 yl) picolinamide, and 1,2,4 triazine pyridine triazole and t hey have been synthesized from simple starting materials in high yield and purity. All ligands are non adentate based off of the triphenoxymethane platform. The target ligands extraction behavior was examined towards a select group of lanthanides. Extractions were performed with metal to ligand ratios of 10:1 from 1M nitric acid aqueous phases into either dichloromethane or 1 octanol. Each of the ligand sets showed limited ability to extract lanthanides with (1,2,4 triazin 3 yl) picolinamide showing a modest selectivity for the smaller, heavier lanthanides (Dy Yb) over the larger lanthanides. The solid sta te structure of ligands with different lanthanides was explored to probe the effect of changing metal radius on the binding pocket and the congruence to ideal trigonal tricapped prismatic geometry. The alkyl substitution on the triphenoxymethane platform was also modulated to determine the effect of steric

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16 hindrance on coordination and extraction A correlation was found between the extraction efficiency and the ability of the ligand to meet the ideal trigonal tricapped prismatic geometry that is seen by lanthanides and actinides in aqueous solution. The binding constants were examined using UV/VIS spectroscopy The largest binding constants correlated moderately well with ligand metal combinations that showed the greatest extraction extent. The kin eti cs of metallation was also explored using UV/VIS spectroscopy with pseudo first order conditions and showed similar behavior to literature examples. Theoretical calculations were performed to analyze the bond character as actinides are known to have an in creased covalent contribution in their bonding that the lanthanides do not show. L iterature ligands that are known selective extractants for actinides over lanthanides were initially examined to validate the theoretical approach The defined methods were then applied to synthesized ligands to determine if any congruence existed. Development of a method to predict ligand propertie s towards preference for actinide coordination and extraction is a work in progress.

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17 CHAPTER 1 INTRODUCTION 1 1 Nuclear P ower Overview Currently in the United States there are 104 operating nuclear power facilities operating at approximately 90% efficiency generating 806.7 billion kw/h of electricity annually The U.S. is the largest single producer of nuclear electricity a nd the combination of Europe and North America constitutes roughly 70% of the net nuclear electricity generation. 1 The total number of U.S. plants has been static in part because public opinion of nuclear power generat ion changed after high profile events like the Chernobyl meltdown in the Ukraine on April 26, 1986 and the near disaster at the Three Mile Island facility in New Jersey United State s on March 28, 1979. Recently there has been a fundamental shift in the pe rspective on electricity uneconomical, and unclean nuclear power has recently made a resurgence because of reactors federal incentive s, the possibility of carbon dioxide controls that could affect coal plants, and volatile prices for natural gas the favored f uel for new power plants for most of the past Congressional Research Service. 2 As of February 2009 there were 18 new applications for licenses to construct commercial reactors in the U.S. The proposed locations are spread over the eastern half of the country showing the willingness to embrace nuclear power production is ubiquitous and also the perceived need to move away from carbon based fuels. 3

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18 1 2 Constituents in Spent Nuclear Fuel Uranium fuel assemblies are used in reactors for three years before they are retired and removed At the end of their life span the constituents are drastically more diverse then when the fuel assembly was first brought online. The nuclear fission process of 235 U generates approximately one third of the period ic table in the spent nuclear fuel (SNF) It is this spectrum of elements that makes storage and remediation of nuclear waste a significant challenge. During the period of 1968 to 2002 approximately 47,000 tonnes of spent uranium fuel was produced according to the U.S. Energy Information Administ ration. 4 This is in addition to waste generated in the array of countries worldwide that also rely on nuclear power for electricity generation in varying degrees covering ever y continent except Antarctica. A main stra tegy proposed for decades for the handling of SNF is storage in repositories that are deemed geologically stable. A significant hindrance to storage of spent nuclear fue l is the long term danger posed by long lived radionuclides (LLRN) present in the wast e stream. T he LLRN that pose the most significant danger are 99 Tc, 129 I, 135 Cs, 237 Np, 242 Pu, 241 Am, and 247,248 Cm with half lives of 10 5 years or greater F uel assemblie s once removed are stored for a three year cooling period in pools of water to allow for breakdown of the shortest lived isotopes, the elemental constituent profile is shown in Figure 1 2 5 The SNF contain s a pproximately 95 % of the parent uranium from the initial purification mostly comprised of 238 U Heavier actinides are generated by neutron capture events that occur when 238 U atoms absorb transient neutrons with subsequent ejection of a beta particle In effect this generates a new element with one extra proton Np Various combinations of these events are the source of all transuranic

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19 elements (Np, Pu, Am, Cm etc ). As can also be seen from Figure 1 2 is a relatively large amount of stable fission products mainly representative of the lanthanide series of elements (Ln). The quantities of isotopes generated per tonne of SNF are shown in Table 1 1 These estimates are for a standard reactor with uranium oxide fuel. 6 These quantities are not large, but as stated above the relative danger to human po pulations over extended periods of time is quite large. T he main source of long term radiation in standard SNF is Pu which has a half life on the order of 1 million years. The next largest contributor on that time scale is the minor actinides (MA) represe nted by Am and Cm. The other fission products lose significant radiotoxicity within 1 thousand years which is negligible on the geological time scale. To treat waste for effective storage these long lived nuclides must be removed to limit the volume of h azardous waste or for treatment to diminish the length of half lives. 6 1 3 Nuclear Waste Treatment Strategies The primary approach taken for treatment of SNF is biphasic extraction. Application of organic phases t o the acidic aqueous phase is an ideal treatment method as it theoretically allows the selective separation of waste constituents. Ligands applied in these systems must include certain key characteristics. First the uptake of metal into the ligand must b e reversible. Second the ligands must be robust in the conditions of high radiation dose and contact with highly acidic solutions. Third the ligands must also have fast rates of complexation and preferably the ligands would not generate any secondary was te. 7

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20 1 3.1 Transmutation As referred to previously transmutation is one proposed treatment strategy to mitigate the long term danger of radioactive nuclides. Transmutation of a radioactive isotope refers to bo mbardment of that isotope with high energy neutrons. This induces fission of the radioactive isotope generating either innocuous isotopes of other elements or more radioactive elements with shorter half lives which more efficiently degrade. The effect is waste that represents a radioactive toxicity danger for a shorter period of time and is therefore more easily handled and stored. The t ransmutation method cannot be applied to the initial waste stream c oming from the spent fuel. SNF contains a much h igher percentage of Ln as compared to the An as seen in F igure 1 2 The Ln have a much larger neutron cross section which hinders transmutation by efficiently shielding the target An isotopes from incoming neutrons. 8 To allow transmutation to be applied in as a waste mitigation strategy development of a n efficient selective separation strategy of the An from the Ln is imperative 1 3.2 Recycling and Treatment Strategies Currently I n Use T here are various systems i n place to handle the waste stream generated from spent nuclear fuel assemblies with each having significant shortcomings. Spent fuel assemblies are dissolved in aqueous nitric acid solutions ranging from 1 6 M. This high level liquid waste (HLLW) can be vitrified in borosilicate glass casings and then sealed in concrete casks for long term storage. This is the common practice in the United States where no recycling initiatives are in effect due to nuclear non proliferation treaties. In all current meth ods th e first recycling process concentrates the remaining U and Pu in the HLLW which is also a necessity for the generation of Pu based weapons.

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21 1 3.2 A P lutonium UR anium EX traction (PUREX) The initial recycling step commonly employed in countr ies that generate SNF is called PUREX which is an abbreviation for P lutonium UR anium EX traction. This method employs tri n butyl phosphate ( TBP Figure 1 4 ) in a contact battery which operates as a multistep, automated extractor for industrial scale separ ations This process relies upon the higher oxidation states of U, Pu, and Np and their concomitant increase in affinity for TBP TBP coordinates strongly to these more oxophilic ions. The affinity of TBP for these ions is much lower at higher pH range s This is an important characteristic because the extractants must allow removal of the metal ions for their reuse otherwise they are not feasibl e for industrial processes. 1 3.2 B DIA mide EX traction (DIAMEX) The outflow of the PUREX process is called the highly active raffinate commonly referred to as HAR because of its high acidity and radioactivity. This waste outflow is treated in a process called the DIAMEX which stands for the DIA mide E x traction process referring to the extractant employed for the se paration, DMODOHEMA in figure 1 4 a malonic acid derivative This step effectively segregates the Ln and minor actinides (Am and Cm henceforth represented by MA) from the various other fission products like Cs, I, and Sr. There are proposed steps for th e treatment of this waste fraction but are not covered here as this work focuses on the An and Ln constituents. 1 3.2 C S elective A cti N ide EX traction (SANEX) At present an effective, environmentally sound method has not been developed to handle the waste fr action containing the Ln and MA Bis(2,4,4 timethylpentyl)d ithiophosphinic acid DTPA in F igure 1 4 is one proposed ligand for the

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22 SANEX process, S e lective A cti N ide EX t raction. This ligand was able to extract Am over 2300 times more efficiently than Eu from a biphasic system 9 11 The drawbacks of dithiophosphinic acid extractants are that they require modified extraction systems which necessitate an increase in waste volume f or pH adjustment it has shown some susceptibility to radioly tic degrada tion and it uses the phosphine sulfide moiety as donor which upon further treatment of the extracted phase creates hazardous solid waste which is non ideal. 12, 13 An alternate ligand extensively studied for application in the SANEX process is bis 1,2,4 triazinyl pyridines (BTP Figure1 5 ). These ligands were first developed by Kolarik 14, 15 in 1999 and were found to ha ve an affinity for Am approximately two orders of magnitude larger than for Eu This selectivity is not observed for other similar terdentate ligands with N donors. These ligand types also suffered fr om radiolytic and hydrolytic degradation in tests with radioactive materials. 1 4 Properties comparison of 4 f and 5f E lements The work reported herein focuses on this final separation step, the segregation of MA from the Ln which most closely correlates w ith the SANEX process This separation problem has been approached by many scientists over the last 70 years but as yet no clear conclusions have been attained for the segregations of these elements for storage. This dilemma exists because of some essen tial sim ilarities between the 4f and 5f elements making their selective complexation difficult. This is superbly exemplified by researchers initially discover ing Mendelevium by separation of a mixture of elements and isotopes on an ion exchange column by predicting the properties of Md and determining which drop the desired isotopes would elute even in the presence of a large excess of similar isotopes of Es and Fm 16

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23 The main attributes exploited in previously studie d systems like alkaline earth and transition metals were based on oxidation state and ionic size. Unfortunately these characteristics are strikingly similar between the 4f and 5f elements. The preferred geometry of both groups of elements is tricapped t rigonal prismatic with a coordination number of 9. It can be seen in Fi gure 1 6 that the ionic radi i are very similar for the Ln and An when in the same oxidation state, as shown +3. This does not allow for strategies employing reagents like crown ethers which are strictly size specific. The similarities to Ln(III) are greater for the transuranics elements heavier than uranium, because for those elements the 5f orbitals are slightly more contracted within the 6d, 7s, and 7p making the +3 oxidation state more favored. 17 Table 1 2 shows the most stable oxidation state for all Ln and An further establishing this point with t he only deviation in the transuranic An being No of the full f orbital block 18 Bk to Lr are included for comparison though they are not relevant to a discussion on SNF treatment strategies because of their very short half lives. Another characte ristic that the two groups of metals parallel one ano ther is their hard/soft acid/base chemistry as outlined by Pearson 19 All Ln and An are described as hard acids. They are commonly described as strong Lewis acids and as such are strongly oxophilic and bind str ongly to oxygen donors. As seen in Table 1 2 s ome An have an array of available oxidation states but this is not consistent between metals and is an inadequate differentiating characteristic for Ln and MA separations One essential difference between the groups of elements is the ability or lack thereof to use the s, d, and f orbitals to some degree in covalent bond formation. The radial extension of the 5f orbitals is greater than for the 4f and can interact covalently

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24 with ligands. There is substantial evidence showing the Ln create essentially ionic bonds which has been fully reviewed by Choppin 20 Careful ligand design allows the exploitation of this trait and has led to extractants with greater selectivi ty for An than Ln. 1 5 Experimental Evidence for Covalency in the B onding of An Complexes It is theorized that an increase in covalency of binding between An and soft donors compared to Ln and the same donors is a source of ligand selectivity in extractio n experiments. A recent study by Gaunt and co workers comparing the bonding for Ln and An with ligand donors were incrementally modulated with respect to their softness. Examination of the solid state structure showed a decrease in the bond lengths with An over Ln and the bonding change was also supported by theoretical calculations. The ligand and metals used were M[(N(EPPh 2 ) 2 )] 3 (M = U, Pu, La, Ce; E = S, Se) and M[(N(EP i Pr 2 ) 2 )] 3 (M = U, Pu, La, Ce; E = S, Se, Te) The An representatives in all cases showed decreasing bond lengths as the donors became s ofter chalcogen represent atives but the disparity between like sized Ln and An was greatest when the donating atom was the softest. The results of the study lend credence to the theory that higher weigh t An like Am and Cm may also have this same effect though most likely diminished as compared to U and Pu. 21 A similar study with tripodal and tetrapodal pyr azine ligands with amino donors on ligands that have sel ectivity for An and Ln showed similar results. 22 24 In another study performed by Bond and co workers 17 three phosphi ni c acid derivatives were compared, Figure 1 7. These compounds were synthesized and the soluti on structures were compared by X ray fine structure, E XAFS to determine an inherent difference between the exceptional ability of 1 4 to coordinate MA compared t o other extractants. It was shown that while 1 5 and 1 6 generated various structures in

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25 solution including dimers and hydrogen bonded monodentate structures that 1 4 took on exclusively the ML 3 form in solution with a bidentate binding mode for all ligan ds. They did not perceive any bond shortening for 1 4 or increased ligation and concluded that there was an increased covalency in the bonding that impacted the structure excluding all solvent and anions but did not impact the bond lengths or coordination number. Another ligand with known preference for An over Ln that has been studied in the solid state and by theoretical calculation is the previously mentioned BTP ligand set. Much of the work presented in this document is based upon structurally similar ligands. In work published by Denecke and co workers 25 EXAFS and time resolved laser induced fluorescence spectroscopy, TRLFS, were exploited to investigate the solution structure of BTP with different Ln and An. The data showed little deviation with respect to the bond lengths from M(III) ions of Ln and An with similar radii though it was determined that Ln needed a much larger excess of ligand to form exclusively ML 3 complexes while for An the e xcess was sm aller. For example, Eu needed an excess of 300:1 while for Cm only 8:1 to form exclusively the ML 3 complex This shows that the stability of BTP complexes is not necessarily directly proportional to the bond length. 1 6 Theoretical Approaches to Eluci dation of Ligand Selectivity Theoretical calculations are frequently used to elucidate the source of specificity in complex formation and extraction. This is a useful approach but when applied to systems with Ln and An issues arise because of the complexi ty of the systems. Specifically the calculations must include open shells, strong electron correlation, and relativistic effects. 26

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26 There have been various studies that have focused on entropy effects of the known 1:3 M:L binding mode but as many similar ligands to BTP show the same binding mode but not the same selectivity this is not a sufficient basis. 27, 28 I nvestigations focused specific ally on ML 3 were L is BTP correlated the population of the inner coordination sphere with the extent of backbonding from metal centered atomic orbitals. This study showed the inner coordination sphere must be strictly controlled to enhance any covalent in teractions from the 5f orbital to the The effect was diminished when either solvent molecules or counter anions were allowed to complex to the metal. 29, 30 One reason often pointed to for the selectivity of BTP is a lowering of the energy of the orbital relative to similar BPY and TERPY ligands. 26, 29, 31 One caveat that should be cove red is that U is used as a model for transuranic elements because of the accessibility of the +3 oxidation state prevalent in the heavier An, its relatively great availability, and the ease of use because it is a limited emitter. Problematically U has been questioned as a good model for such elements because of some clear deviation in properties and reactivity especially seen though detailed theoretical investigations. This is shown by the highly fluxional redox chemistry and the deviation of U f orbit al energy compared to Am and Cm is excessively large. 31, 32 1 7 Preorganization of Donors and the Chelate Effect The chelate effect is commonly understood from the general chemistry level to a ffect coordination of ligands and to promote more stable complexes because of this entropy effect Systems tend towards more dis order or more atoms so l ogically, i f more donors are included into one ligand then less are needed to fill the coordination s phere

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27 coordination. Ln and An both have large inner coordination sphere s with a coordination number typically around 9. Removal of the solvent and anionic constituents with fewer th an 9 molecules would be described as an entropic advantage and often leads to increased performance in extraction experiments 33 Constraint of donors into a preorganized system also in many cases increases the se lectivity for specific metals. Limiting the degrees of freedom of movement for donors lowers the array of metals that fit ideally in the binding cavity. T he ide al geo metry preferred by Ln(III) and An(III) is the trigonal tricapped prismatic orientation. Figure 1 8 sho ws common scaffold in the literature for tethering of Lewis basic sites. 34 The benefits of preorganization are clearly shown in work performed by Arnaud Neu and co workers in which ligands including a calix [n] arene scaffold ( 1 8, Figure 1 8 ) with carbamoylmethylphosphineoxide (CMPO) donor groups and CMPO based ligands with various denticities were compared (Figure 1 9) 35 The number of phenyl rings n can be modulated in cali x [n] arenes allowing precise c ontrol of the binding environment. Earlier w ork by Ferraro and co workers showed that the CMPO extracted species is of the form M(CMPO) 3 (NO 3 ) 3 with each carbonyl o xygen weakly bound to the metal whi le also coordinating a nitric acid molecule to the complex ( Figure 1 10 ) 36 O rganization up on the scaffold induced a drastic improvement in the extraction performance from bidentate 1 11 to calyx [4] arene based 1 14 for extraction from a 1M nitric acid aqueous phase into o nitrophenyl hexyl ether (NPHE) The extraction percent age increased from approximately 0.1% for both Eu and Am for the bidentate derivative (1 11) to quantitative extraction after one contact with the octadentate ligand

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28 (1 14, Table 1 3 ) Clearly combination of donors to limit the number of ligands required for phase transfer of Ln and An is necessary for an efficient process and fo r minimization of ligand concentrations. Macrocyclic rings whil e showing precise selectivity at times often suffer from difficult synthesis and more debilitating for industrial purposes very slow rates of metallation. The scaffold of choice used in this work is the triphenoxymethane platform. It is a highly preorg anized non macrocyclic ligand due to it s stable orientation with all the phenolic oxygens pointing in the same direction ( 1 10, Figure 1 8). This orientation has been established by solid state structure and by calculation. 37 1 8 Research Objectives The goal of the work presented here is to design and synthesize ligands that can selectively coordinate An ions over Ln ions in biphasic systems. Towards this goal different ligands were synthesized containing vario us combinations of heterocyclic donors. The extraction efficiency towards a select group of Ln was examined. Also the binding constants and rates of metallation were measured using UV/VIS spectroscopy. To gauge the quality of design towards selectivity f or An semi empirical and theoretical calculations were performed. The extent of covalency was discern ed from calculation result and compared with literature examples.

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29 Figure 1 1 Total Number of U.S. Nuclear Power Plants from 1960 to 2008. Figure 1 2 Constituents of Spent Nuclear Fuel assemblies upon retirement. 5 0 20 40 60 80 100 120 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Number of Nuclear Power Plants Uranium 95.5% Stable Fission Products 3.1% Short lived Cs and Sr 0.2% Long lived I and Tc 0.1% Other Long lived Fission Products 0.1% Plutonium 0.9% Minor Actinides 0.1% Other 4.5%

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30 Figure 1 3 Schematic of common spent fuel processing techniques Figure 1 4 Representative examples of e xtractants used in recycling proc esses Figure 1 5 Bis triazinyl pyridine (BTP) used in SANEX process as alternative to DTPA.

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31 Figure 1 6 Comparison of Ln(III) and An(III) ionic radii all with C.N. = 6. Data for Th only available for Th 4+ 38 Figure 1 7 An ligands compared to determine covalent bonding effect on bonding and structure. Figure 1 8 Sample of common preorganized scaffolds used in preorganization of donor groups. 0.85 0.90 0.95 1.00 1.05 1.10 1.15 Ionic Radius () Ln(III) An(III) Pa Am Cm Eu Ac Th U Np Pu La Ce Pr Nd Pm Sm Gd Tb Dy Ho Er Tm Yb Lu

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32 Figure 1 9 Extractants used for comparison of preorg anization effect with the CMPO donor set towards Eu and Am from a 1M nitric acid aqueous phase into NPHE. Figure 1 10 Extracted species for Am by CMPO from an acidic aqueous phase into an organic phase. 36 Table 1 1 Masses of long lived radionuclides from 1 tonne of SNF. 6 Name Symbol g LLRN/tonne of U (g) Technecium Tc 822 Iodine I 170 Cesium Cs 353 Neptunium Np 416 Americium Am 323 Curium Cm 26

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33 Table 1 2 Rel atively accessible oxidations states of the Ln and An. 18 La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 3 3*,4 3*,4 3 3 2*,3 2,3* 3 3*,4 3 3 3 3 2,3* 3 For e lements with multiple oxidation states asterisk de notes most stable state Table 1 2. (Cont.) Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr 3 4 4 3, 4, 5, 6* 3, 4, 5*, 6 3, 4*, 5, 6, 7 3*, 4, 5, 6 3*,4 3*,4 3 3 2,3* 2,3* 2*,3 3 Table 1 3 Extraction percent for preorganized CMPO ligands from 1M nitric acid aqueous solution into NPHE. 35 Eu Am 1 11 < 0.1 < 0.1 1 12 54 64 1 13 93 94 1 14 >99 >99

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34 CHAPTER 2 BIPYRIDINE BASED EXT RACTAN T S TETHERED TO THE TR IPHENOXYMETHANE PLATFORM SYNTHESIS AND EX TRACTION PROPERTIES 2 1 Introduction All ligands that have successfully separated An from Ln have included some combination of donors softer than oxygen. It has been theorized this affinity for An is due to increased covalency in the metal ligand bonding. 39 E xperimentally the ligands with the greatest amount of success without the use of phosphorous exclusively contain nitrogen donors that are commonly included in heterocyclic rings. Bipyridine is ubiqu itous in coordination chemistry for it s interesting spectral properties including the original tris bipyridine Ru(II) complex reported in 1985 40 Because of this known coordination chemistry and because it has softer nitrogen donors compared to many oxygen based extractant s it w as pursued as a novel target extractant As mentioned previously the terdentate extractants that show the highest selectivity towards An over Ln exhibit the ML 3 coordination geometr y in highly acidic solution and in the solid state. Preorganization of donors onto a triphenoxymethane platform directs extractant systems to take on this coordination because all the donor groups are in close proximity The solid state structure of a pr eorganized heptadentate bipyridine complex has been identified showing bi pyrid in e and La (Figure 2 1) 41 In this work the bipyridine moieties only had to compete with perchlorate for preferential bind ing to the metal center so experimentation is necessary to see if complexation can be achieved with a large denticity ligand in the presence of strongly competing ligands like nitrate

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35 A common extractant used f or metal separations in biphasic systems bis (5,6 dialkyl 1,2,4 triazine 3 yl) 2,2 bipyridine (BTBP) shown in Figure 2 2 42 This ligand has been applied to selective actinide extraction process ( S ANEX ) systems and shown to have selectivity for Am(III) over Eu(III) with separation factors on the order of 180 from highly acidic aqueous phases 43 45 D er ivatives of this extractant were synthesized that showed adequate stability in realistic extraction conditions of high acidity and radiotoxicity. 46 Based on the success of this ligand a novel target ligand was de signed incorporating bipyridine to investigate if this moiety was the site of the preferential binding for An over Ln Previous work by Dr. Kornelia Matloka of the Scott group showed that a preorganized diglyco lamidic (DGA) based ligand with two carbonyl oxygen donors and an ethereal oxygen donor showed a preference for Ln over An (Figure 2 3) according to the distribution ratio D (D = [M Org ]/[M Aqu ]) in extraction experiments. 47 Shifting the donor set away from purely oxygen donors to bipyridine for the bulk of the donor groups was a shift towards softer donors as compared to the DGA ligand which are known to have increased affinity for An compared to Ln. 48 2 2 Result s and Discussion 2 2.1 Synthesis of Target Ligands The ligand design centered on synthesis of a bipyridine derivative with a carboxylic acid group in the 6 position that could be exploited for tethering to a scaffold like triphenoxymethane by conversi on to an amide linkage The scheme followed to synthesize the l igand arm is shown in Figure 2 4 and is based on previously reported synthetic procedures. 49 All synthetic steps were performed with similar yield an d purity as the literature report

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36 The triphenoxymethane platforms used were synthesized based on previo usly reported synthetic schemes, 2 2 50 2 3 a c 37, 51 and 2 4 while a novel triphenoxymethane was based on a similar molecule reported by Dr. Ranjan Mitra formerly of the Scott group. 52 All triphenoxymethane platforms are depicted in Figure 2 5 T he alkyl substitution was modified on the triphenoxymethane platform to modulate the solubility and probe steric effe cts on the donor arms from increasing bulk of the alkyl groups attached to the phenols. The synthetic scheme and all target ligand s are sh own in Figure 2 6 In all cases the synthesis was initiated by generation of the acyl chloride derivative of 2 1 using thionyl chloride (Step i Figure 2 6 ). Condensation of the corresponding triphenoxymethane scaffold (2 2 or 2 3 a c ) with 2 1 Acyl and di methylaminopyridine resulted in the target ligands 2 5 or 2 6 a c (Step ii, Figure 2 6) 2 2.2 Solid State Structure of Eu( 2 6 c ) 3+ The solid state structure of 2 6 c with Eu was determine d by X ray diffraction to probe the metal coordination environment. This data is being harvested from a partial solution be cause of data quality issues and t he crystal may be twinned. The main conclusion that can be drawn from this structure is that t he inner coordination sphere of the metal was replaced by 2 6 c and the E u was completely encapsulated removing all solvent and counter anions Compound 2 6 c crystallized in a rhomdohedral unit cell, containing 1/3 of the overall structure and e uropium triflate was used to generate the complex It is preferable to have nitrat e as the counter anion to parallel the active species in extraction experiments but nitrate derivatives suffered from poor crystallinity. 2 2.3 Binding Constant Studies The binding constant, defined here as K = [ML] 3+ /[M] 3+ [L] for the reaction M 3+ + L = ML 3+ is a necessary descriptor when analyzing the quality of an extractant. Though

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37 the extraction process across a phase boundary is a complex process high coordination strength is always a necessity. Binding constants were determined using UV/V IS spec troscopy in acetonitrile to ensure fast equilibration at room temperature Ligands were typically dissolved in 3mL of acetonitrile at a concentration of approximately 2 x 10 5 M. Addition volumes were varied depending on metal titrant concentration to ac hieve a 1 to 1 M:L ratio with approximately 10 additions. Depending on the binding strength more additions may have been necessary. A representative collection of spectra is shown in Figure 2 8 for the titration of 2 6 b with Yb (NO 3 ) 3 The binding consta nt values for La, Eu, and Yb with 2 6 b ar e summarized in Table 2 1 with comparison to other bipyridine terdentate ligands reported in the literature ( 2 7 and 2 8 Figure 2 9) 53 The binding constants observe d for 2 6 b represent an increase which is larger in magnitude than the error from the similar 6 (5,6 dipentyl 1,2,4 triazin 3 yl) bipyridine, 2 7. The difference between the maximum and minimum value for 2 6 b and 2 7 shows negligible deviation and th ese two ligands are expected to have similar extraction profiles. The values for 2 8 are not only larger for all metals tested but the difference between Yb and La is also much larger, 3.2 log units indicating that the incorporation of 1,2,4 triazine ring s has a substantial effect on the coordination properties compared to bipyridine amide donors Large discrepancies were not expected as the Ln s how limited deviation in behavior across the series and all tested metals were in the +3 oxidation state The cause of increase affinity for Yb over La for 2 8 was not discussed or explored in the report. These experiments are performed in conditions different from the extraction conditions but the results are proportional to the extractant strength across a n aqu eous

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38 organic phase boundary. This type of analysis does not model the effect of solubility on the extractant performance in biphasic systems 2 2.4 Biphasic Extraction Studies The fundamental goal of all ligand design schemes is efficien t extraction. Due to the limited access of most An because of their inherent hazard extractions were performed with a select group of Ln. In all cases equal volumes of an organic phase containing the ligand was contacted with a 1M nitric acid aqueous solution of the chose n metal at 1 x10 4 M. Commonly the ligand was tested at a 10:1 molar ratio for L:M but was at times increased to determine the effect of a larger quantity of ligand on the extraction efficiency. The organic phase was either dichloromethane or 1 octanol. 2 2.4 A Solubility i ssues An unforeseen difficulty with this family of ligands was the solubility of the free and complexed ligands. For example, Figure 2 10 depicts one extraction result for compound 2 5 from the standard acidic aqueous soluti on into dic hloromethane represented according to the extraction percent (E%) defined as the percentage of metal removed from the aqueous phase after extraction A t first glance the data suggests promising results but these results were not reproducible. Upon compl etion of the 12 hour phase contact time the samples were routinely allowed to sit for two hours to allow for separation of phases. Ligand 2 5 had significant solubility problems after extraction. The free ligand was highl y soluble in the organic phase b ut after the extraction experiment the layers would not separate in the two hour time period If a 1mL aliquot of the aqueous layer was able to be sampled then extraction results were collected but this was not reasonable for consistent results to be obta ined. The larger ligands with greater steric bulk also had separation issues with some extractions but the

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39 difficulty decreased as the steric bulk increased and results were accordingly of higher quality. Crystals were taken from an extraction experiment with 2 6 a that grew at the aqueous/organic phase boundary. The crystals were analyzed by 1 H NMR spectroscopy to determine if the crystals were of the metallated complex; however, t he sample was actually 2 6 a in its protonated form. The two spectra are sh own in Figure 2 11 and clearly large deviation of the spectrum resulted. Protonation can severely hinder the extraction performance. 2 2.4 B Reproducible extraction r esults The extraction results for 2 6 a c are summarized in Figure 2 12 It is clear that all three ligands have a weak affinity for extraction of Ln from 1M nitric acid aqueous phases into dichloromethane. The ligand to metal ratio was 10:1 which is extremely small as compare d to industrial processes that commonly have ratios on the order of 100,000:1 for mono and bidentate ligands like tri nButyl phosphate ( TBP Figure 1 4 ) Conclusions should not be hastily drawn from the data in Figure 2 12 as it seems to indicate improved activity for 2 6 a over 2 6 b and 2 6 c but t he deviation between th e data sets is near the error for the e xperiment. Figure 2 13 is shown containing the same data set as Figure 2 12 with the extraction efficiency for the di tPentyl triphenoxymethane wit h diglycolamidic donor arms (2 9 ) synthesized by Dr. Kornelia Matloka formerly of the Scott group included This oxygen based extractant is a highly efficient ligand for the latter half of the lanthanide series. Clearly these bipyridine based extractants are not efficient extractors of Ln from acidic aqueous phases as the y do not contain as many oxygen donors which the Ln, as hard acids, prefer 47, 54

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40 One facet of extraction design is taking a green approach when deciding which reagents and solvents to use. This is a trend in chemistry and necessary to find conditions that are industrially viable. The extraction efficiency of 2 6 a and 2 6 b were examined for Ln from 1 octanol as dichloromethane is not congruent with any industrial application. In both cases the ligands had no ability to extract Ln into 1 octanol. In order to define if the functioning regime is thermodynamic or solubility based an alternate counter anion can be used to modify the solubility of the extracted complex at the phase boundar y. The most common choice in the literature is chlorinated cobalt(III) bis(dicarbollide) (COSAN) 55 57 Frequently the effect of adding COSAN is increased extraction ef ficiency because of increased complex solubility but insignificant change on the separation factor because COSAN does not discern between ML x complexes For the experiments the added COSAN concentration was 3 x 10 3 M, the metal was 1 x10 4 M, and for 2 6 b was 1 x 10 3 M for a ratio of 30:10:1. The organic layer employed was dichloroethane. The resul ts are summarized in Figure 2 14 were the extraction percentages with COSAN were actually diminished compared to the COSAN free system. This small decrease co uld be attributed to the solvent change but clearly the system was little affected by addition of COSAN. Though COSAN frequently has a positive effect on extraction systems this result is not unprecedented. W ork perfo rmed by Krejzler and co workers using 6 (1,2,4) bipyridine showed diminished extraction a s the concentration of COSAN was increased 55 The author postulated that protonation of the neutral hetero cyclic ligand induced formation of an adduct with the anionic COSAN preventing extraction More extractions are necessary to determine the ideal COSAN

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41 concentration and to see if a synergistic concentration can be found or if COSAN is antagonistic at all concentrations with this ligand system. 2 3 Conclusio ns A new family of ligands has been synthesized in high yield and purity. Their effectiveness towards the separation of Ln and An was impeded due to emulsification issues in the extraction experiments and a limited ability to extract select metals was sho wn. A necessary prerequisite for An selectivity is limited extraction ability towards Ln but more experiments are needed to determine if the ligands can be effective for this purpose. Binding constant experiments were conducted with 2 6 b A slight prefer ence for Yb>Eu>La was shown with a difference of approximately 1.4 log units between log( K Yb ) and log( K La ) These values are congruent with a small preference for smaller, heavier Ln in the extraction results. According to the solid state structure of Eu (SO 3 CF 3 ) 3 with 2 6 c the ligands coo rdinate in a 1: 1 fashion and with a coordination number of 9. The entire inner coordination sphere is filled by 2 6 b to the exclusion of anions and solvent. A solid state structure with nitrate counter anions is prefer able but not determined due to crystal quality issues and the structure in the presence of highly competitive nitrate anions is not known at this time.

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42 2 4 Experimental 2 4.1 General Considerations 1 H and 13 C NMR spectra were recorded on a Gemini300, V arian300, or Mercury300 NMR instrument at 299.99 MHz for the proton channel and 75.47 MHz for the carbon channel. All UV/ VIS spectra were reco rded on a V ar ian Cary 50 spectrophotometer. E ach sample analyzed by mass spectrometry was dissolved in appropria te solvent and underwent direct injection through an autosampler, followed by ESI or APCI analysis with methanol (with or without 0.2% acetic acid ) as mobile phase. For MALDI, the solution was usually added onto the matrix spot of dithranol, cyano 4 hydroxycinnamic acid, dihydroxybenzoicacid or terthiophene. Solvent was used only when necessary for DART. The ions were detected with the Agilent 6210 TOF MS while the data was Elemental analyses were pe rformed at the in house facilities at the University of Florida. All solvents unless otherwise noted were used as received and either HPLC or ACS grade. Metal nitrate salts were purchased from Sigma Aldrich. They were dried under vacuum but otherwise us ed as received. Metal solutions were made using 18 Millipore deionized water and TraceMetal grade HNO 3 (Fisher Scientific). Arsenazo(III) dye was used as a UV/VIS sensitizer for all metal extraction experiments. Compound 2 1 was synthesized according to a previously reported procedure 49 2 4.2 Binding Constant UV/VIS Measurements For all binding constant experiments a quartz cuvette was used along with deoxygenated acetonitrile to allow for analysis down to = 240nm. 3mL of the ligand solution at approximately 7 x 10 5 M were pipetted into the cuvette using an automatic

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43 pipettor. The background consisted of tetrabutylammonium nitrate at a concentration of 1 x 10 2 M to ensure that the ionic strength was constant throughout. The free ligand spectrum was collected followed by addition of a spike of metal solution with a concentration approximately 2 x 10 3 M. The spike vo lume was chosen to add a 1:10 molar ratio M:L for each spike. The solution was then stirred for 5 minutes and the spectrum collected. This was repeated until the system reached equilibrium. The data was processed using Reactlab EQUILIBRIA created by Jplus Consulting. This global analysis software fits the UV/VIS spectral trends and outputs the binding constant. 2 4.3 Metal Extraction Experiments The procedure for metal extraction experiments followed a previous literature report. 58 4mL solutions of the ligand in the chosen organic solvent were contact ed with 4mL of the 1M nitric acid aqueous phase containing the metal at 1 x 10 4 M in 20mL borosilicate scintillation vials with plastic cone lined urea caps (Fisher Scientific). Each metal was tested in triplicate. The vials were sealed and contacted for 24 hours on a shaker table The vials were then allowed 2 hours for phase separation. 1mL aliquots of the aqueous phase were then extracted with an automatic pipettor and placed in 25mL volumetric flasks and diluted to the mark with formic acid/sodium f ormate with 2.5mL of the Arsenazo(III) dye added. The UV/VIS spectrum of each metal was collected at = 655nm. The result was compared against the spectrum of the sampled metal solution with no extraction according to the formula: E% = 100*[(A 1 A)/(A 1 A 0 )] where A is the absorbance of the extracted aqueous phase, A 1 is the absorbance of the unextracted metal solution and

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44 A 0 is the absorbance of the metal free nitric acid solution diluted in the buffer. Another descriptor was the distribution rations calculated by the following equation: D = [M org ]/ [M aq ]. [M org ] is the concentration of the metal in the organic phase and [M aq ] is the corresponding concentration of the remaining metal in the aqueous phase. As these two quantities were not both measured the equation used to determine D was b ased on the extraction efficiency: D = E%/(100 E%). The final descriptor used was the separation factor which is a measure of the selectivity of a ligand for one metal as compared to another metal under the same extraction conditions and this is calculate d by: SF m/n = D m /D n 2 4.4 Synthetic Procedures 2 4.4A Compound 2 4 A 15.31g portion of 2 4 ( 11.7mmol) was combined with sodium azide (6.85g, 105mmol) in 325mL of DMF in a dry 500mL Schlenk flask fitted with a reflux condenser and the reaction mixture was heated to reflux overnight. The solution was allowed to cool to room temperature when 250mL of water was added and the solution extracted with dichloromethane (3 x 100mL). The combined organics were washed with water (3 x 100mL) and brine (1 x 100mL). T he organics were dried with sodium sulfate and the solvent was removed under reduced pressure yielding pure 4 8 (10 .82g, 100%). 1 H NMR (CHLOROFORM d) ppm 0.52 (t, J=7.5 Hz, 9 H), 0.58 (t, J=7.5 Hz, 9 H), 1.15 (s, 18 H), 1.39 (s, 18 H), 1.48 (q, J=7.3 Hz, 6 H), 1.75 (br. s., 6 H), 3.14 4.00 (m, 12 H), 6.40 (s, 1 H), 7.10 (dd, J=13.2, 2.3 Hz, 6 H). 13 C {1H} NMR 9.1, 9.5, 28.5, 29.4, 35.2, 36.8, 3 7.7, 38.6, 39.2, 51.8, 70.5, 125.1, 127.8, 137.4, 140.3, 143.2, 152.6. Anal. Calcd. For C 55 H 85 N 9 O 3 : C, 71.78; H, 9.31; N, 13.70. Found: C, 71.90; H, 9.62; N, 13.50.

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45 2 4.4 B Compound 2 5 A 2.87g portion of 2 1 ( 14.3 mmol) was placed in a flame dried 250mL r ound and 100mL of thionyl chloride was added This mixture was heated to reflux and stirred overnight. The thionyl chloride was removed under reduced pressure. The resulting brown residue was dissolved in CHCl 3 and the solution was cooled to 0 C. Dimet hylaminopyridine (2.9g, 24 mmol) and 2 2 (1.02 g, 2.4mmol) were dissolved in CHCl 3 (40mL) and slowly injected into the reaction vessel. The brown solution was warmed to room temperature and stirred for two days. The organics were washed 2 times with a 10% HCl solution (100mL) followed by washings with 1M NaOH (100mL) and brine (100mL). The solvent was dried with anhydrous sodium sulfate and then removed under reduced pressure. The brown residue was then stirred in refluxing ethanol. Upon cooling to room temperature a precipitate formed which was collected by filtration. This process was repeated two more times affording 2 5 ( 1.64 g 70 %) was collected by filtration. 1 H NMR (CHLOROFORM d ) ppm 2.36 (s, 9 H), 3.65 (s, 9 H), 6.65 (s, 1 H), 6.94 (d, J =1.9 Hz 3 H), 7.08 (dd, J =7.0, 5.3 Hz, 3 H), 7.59 (t, J =7.7 Hz, 3 H), 7.87 7.96 (m, 6 H), 8.19 (dd, J =11.1, 7.9 Hz, 6 H), 8.45 (d, J =7.9 Hz, 3 H), 8. 53 (dd, J =4.7, 0.8 Hz, 3 H), 9.90 (s, 3 H) 13 C { 1 H} NMR 16.7, 37.7, 60.2, 120.2, 121.2, 121.8, 122.3, 123 .6, 124.1, 132.1, 133.0, 137.2, 138.5, 148.9, 149.4, 153.3, 154.4, 161.7. Anal. calcd. for C 59 H 51 Cl 2 N 9 O 6 : C, 67.30; H, 4.88; N, 11 .97. Found: C, 66.35; H, 4.84 ; N, 11.68. 2 4.4 C Compound 2 6 a A 2.06g portion of 2 1 ( 10.5mmol ) was placed in a flame dried 250mL round bottom and 100mL of thionyl chloride was added This mixture was heated to reflux and

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46 stirred overnight. The thionyl chloride was removed under reduced pressure. The resulting brown residue was dissolved in CHCl 3 and the solution was cooled to 0 C. Dimethylaminopyridine ( 2.09g, 17.2mmol ) and 2 3 a ( 1.11g, 1.72mmol ) were dissolved in CHC l 3 (40mL) and slowly injected into the reaction vessel. The brown solution was warmed to room temperature and stirred for two days. The organics were washed 2x with a 10% HCl solution (100mL) followed by washings with 1M NaOH (100mL) and brine (100mL). The solvent was dried with anhydrous sodium sulfate and then removed under reduced pressure. The brown residue was recrystallized from acetonitrile and cryst alline 2 6 a (1.78g 86%) was collected by filtration 1 H NMR (CHLOROFORM d ) ppm 1.19 (s, 27 H), 2.24 (s, 9 H), 3.57 (t, J =5.1 Hz, 6 H), 3.79 (q, J =5.6 Hz, 6 H), 6.95 6.98 (m, 1 H), 7.01 (m, J =6.5 Hz, 6 H), 7.20 (ddd, J =7.5, 4.8, 1.0 Hz, 3 H), 7.71 (td J =7.7, 1.8 Hz, 3 H), 7.82 (t, J =7.8 Hz, 3 H), 8.11 (dd, J =7.6, 1.1 Hz, 3 H), 8.36 (d, J =7.9 Hz, 3 H), 8.45 (dd, J =7.9, 0.8 Hz, 3 H), 8.58 (d, J =4.8 Hz, 3 H), 8.66 (t, J =6.1 Hz, 3 H) 13 C { 1 H} NMR 31.6, 34.4, 37.1, 40.0, 71.1, 121.2, 122.5, 123.6, 124 .3, 126.0, 126.3, 130.2, 136.5, 138.4, 146.1, 149.1, 149.7, 152.8, 164.6 Anal. calcd. for C 73 H 79 N 9 O 6 : C, 74.40; H, 6.76; N, 10.70. Found: C, 74.27; H, 6.88; N, 10.48. 2 4.4 D Compound 2 6 b A 3.55 g portion of 2 1 ( 17.7 mmol) was placed in a flame dried 2 50mL round bottom and 1 5 0mL of thionyl chloride was added This mixture was heated to reflux and stirred overnight. The thionyl chloride was removed under reduced pressure. The resulting brown residue was dissolved in CHCl 3 and the solution was cooled t o 0 C. Dimethylaminopyridine ( 4.51g, 36.9 mmol) and 2 3 b ( 2.97g, 3.69 mmol) were dissolved in CHC l 3 (40mL) and slowly injected into the reaction vessel. The brown solution was

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47 warmed to room temperature and stirred for two days. The organics were washed 2 x with a 10% HCl solution (100mL) followed by washings with 1M NaOH (100mL) and brine (100mL). The solvent was dried with anhydrous sodium sulfate and then removed under reduced pressure. The brown residue was recrystallized from acetonitrile and crystal line 2 6 b (3.23 g 62 %) was collected by filtration. 1 H NMR (CHLOROFORM d ) ppm 1.25 (s, 18 H), 1.28 (s, 18 H), 3.27 4.71 (m, 12 H), 6.71 6.85 (m, 1 H), 7.18 (d, J =2.5 Hz, 6 H), 7.45 (d, J =2.5 Hz, 3 H), 7.62 (td, J =7.8, 1.7 Hz, 3 H), 7.81 (t, J =7.8 Hz 3 H), 8.17 (dd, J =7.6, 1.1 Hz, 3 H), 8.51 (m, J =1.1 Hz, 6 H), 8.57 8.62 (m, 3 H), 8.99 (t, J =5.9 Hz, 3 H) 13 C { 1 H} NMR 31.5, 31.6, 34.5, 35.5, 40.1, 70.8, 121.1, 122.1, 122.5, 123.3, 124.0, 127.1, 136.9, 137.3, 138.1, 142.1, 144.9, 149.0, 149.4, 153.2, 154.7, 154.9, 164.5 2 4.4 E Compound 2 6 c A 2.63g portion of 2 1 ( 13.1 mmol) was placed in a flame dried 250mL round bottom and 1 5 0mL of thionyl chloride was added This mixture was heated to reflux and stirred overnight. The thionyl chloride was r emoved under reduced pressure. The resulting brown residue was dissolved in CHCl 3 and the solution was cooled to 0 C. Dimethylaminopyridine ( 3.34g, 27.3 mmol) and 2 3 c ( 2.32g, 2.74mmol) were dissolved in CHCl 3 (40mL) and slowly injected into the reaction vessel. The brown solution was warmed to room temperature and stirred for two days. The organics were washed 2x with a 10% HCl solution (100mL) followed by washings with 1M NaOH (100mL) and brine (100mL). The solvent was dried with anhydrous sodium sulf ate and then removed under reduced pressure. The brown residue was recrystallized from ethyl acetate and crystalline 2 6 c (2.52 g 66 %) was collected by filtration 1 H NMR (CHLOROFORM d )

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48 ppm 0.42 0.58 (m, 18 H), 1.18 (br. s., 18 H), 1.26 (br. s, 18 H), 1.50 (q, J =6.8 Hz, 5 H), 1.62 (br. q, J =6.5, 6.5, 6.5 Hz, 5 H), 3.44 (br. s., 3 H), 3.79 (br. s., 6 H), 4.37 (br. s., 3 H), 6.70 (s, 1 H), 7.04 (d, J =2.0 Hz, 3 H), 7.14 7.21 (m, 3 H), 7.29 (d, J =2.3 Hz, 3 H), 7.63 (td, J =7.8, 1.7 Hz, 3 H), 7.79 (t, J =7.8 Hz, 3 H), 8.16 (d, J =7.6 Hz, 3 H), 8.50 (dd, J =9.3, 8.2 Hz, 6 H), 8.59 (d, J =4.5 Hz, 3 H), 8.96 (t, J =6.1 Hz, 3 H). 13 C { 1 H} NMR 29.5, 35.1, 36.9, 37.6, 38.1, 39.2, 40.0, 70.2, 121 .1, 122.1, 123.2, 124.0, 124.8, 127.9, 136.9, 137.6, 138.1, 140.1, 142.8, 149.0, 149.3, 153.0, 154.6, 154.9, 164.5 2 4. 4 F Compound Eu( 2 6 c ) (SO 3 CF 3 ) A 0.26g portion of 2 6c ( 0.19mmol) was dissolved in a 20mL of THF. A twofold excess of Eu(SO 3 CF 3 ) 3 was di ssolved in a minimal amount of THF and the solution transferred into the reaction vessel drop wise. A w hite precipitate formed within minutes. The mixture was stirred for 4 hours and then the solid collected on a fritted filter. Crystals suitable for X ray diffraction were grown by diffusion of pentane into ethanol. Anal. calcd. for C 91 H 109 EuF 9 N 9 O 15 S 3 : C, 54.98; H, 5.53; N, 6.34. Foun d: C, 53.51; H, 5.71; N, 6.42 2 4.5 X Ray Structure Solution Structure solutions were obtained by Dr. Patrick Hilleshe im and Dr. Khalil Abboud. X Ray intensity data was collected at 100 K on either a Bruker DUO or Bruker SMART diffractometer using MoK radiation ( = 0.71073 ) or CuK ( = 1.54178 ) and an APEXII CCD area detector. Raw data frames were read by program SAINT and integrated using 3D profiling algorithms. The resulting data was reduced to produce hkl reflections, intensities, and estim ated standard deviations. Structures were solved and refined in SHELXTL6.1 59, 60 using full matrix least squares refinement. Where

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49 necessary, the program SQUE EZE 61 a part of the PLATON package 61 of crystallographic software, was used to calculate the solvent disorder area and re move its contribution to the overall intensity data. Figure 2 1 Example structure of heptadentate bipyridine complex coordinated to UCl 2 41 Figure 2 2 Bis (5,6 dialkyl 1,2,4 triaz in 3 yl) bipyridine (BTBP) as an example of bipyridine based extractants.

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50 Figure 2 3 Distribution ratio of preorganized DGA triphenoxymethane derivative (diamonds) and terdentate DGA at three times the concentration (squares) towards select group of Ln from 1M HNO 3 into dichloromethane Figure 2 4 Synthetic scheme for 6 carboxy bipyridine. 49 Figure 2 5 Triphenoxymethane scaffolds used for preorganization of donor groups. 1.5 0.0 1.5 3.0 La Ce Pr Nd Eu Gd Tb Dy Er Tm Yb Log(D)

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51 Figure 2 6 Synt hetic schemes for nonadentate bipyridine ligands. Figure 2 7 Solid state structure of Eu(2 6 c )(SO 3 CF 3 ) 3 Th e counter anions solvent, alkyl disorder, and hydrogens have been removed for clarity. Atoms represented by standard radii Red = oxygen, bl ue = nitrogen, grey = carbon, green = europium.

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52 Figure 2 8 Representative plot of spectra from titration of 2 6 b with Yb(NO 3 ) 3 in acetonitrile. ([L] approx. 2 x 10 5 M) Figure 2 9 Ligands used in binding constant comparison. 0 10 20 30 40 50 60 70 245 265 285 305 325 345 (cm 1 M 1 ) Thousands (nm)

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53 Figure 2 10 Ex traction results for 2 5 from 1M nitric acid into dichloromethane. [L] = 1 x 10 3 M, [M] = 1 x 10 4 12 hour contact. Figure 2 11 Comparison of 1 H NMR spectra in CDCl 3 for 2 6a ( bottom ) and a crystal grown in contact with a 1M HNO 3 aqueous phase (top) indicating structural change most likely due to protonation. 0.0 5.0 10.0 15.0 20.0 25.0 30.0 La Ce Pr Nd Eu Gd Tb Dy Er Tm Yb E%

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54 Figure 2 12 Extraction data for 2 6a (triangles), 2 6b (diamonds), and 2 6c (squares) from 1M nitric acid into dichloromethane. [L] = 1 x 10 3 M, [M] = 1 x 10 4 12 hour contact. Figure 2 13 Extraction data for 2 6a (triangles), 2 6b (diamonds), 2 6c (squares), and 2 9 (circles) from 1M nitric acid into dichloromethane. [L] = 1 x 10 3 M, [M] = 1 x 10 4 12 hour contact. 0 10 20 30 La Ce Pr Nd Eu Gd Tb Dy Er Tm Yb E% 0 20 40 60 80 100 La Ce Pr Nd Eu Gd Tb Dy Er Tm Yb E%

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55 Figure 2 14 Results comparing extraction with 2 6 b with COSAN (diamonds) and without (squares) from 1M nitric acid into dichloromethane. [L] = 1 x 10 3 M, [M] = 1 x 10 4 [COSAN] = 3 x 10 3 M, 12 hour contact. Table 2 1 Binding constant data for complexes of 2 6 b with La, Eu, and Yb. All values refer to 1:1 comple xes. 2 6 b 2 7 2 8 log(K) +/ log(K) +/ log(K) +/ La 3.106 0.021 2.8 0.1 4.8 0.3 Eu 3.525 0.012 3.6 0.1 5.7 0.3 Yb 4.574 0.005 4.19 0.08 8.0 0.2 Reference : Arnaud Neu et al., Inorg. Chem. 2010, 49, 1363 1371 0.0 10.0 20.0 30.0 La Nd Eu Dy Yb E%

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56 CHAPTER 3 BIS (1,2,4 TR IAZIN 3 YL) PYRIDINE EXTRACTANT S TETHERED TO THE TRIPHENOXYMETHANE PL ATFORM SYNTHESIS AND EXTRAC TION PROPERTIES 3 1 Introduction To date t he most effective ligand found containing C, H, O, and N exclusively is the family of ligands based on the 2,6 bis (5,6 dialkyl 1,2,4 triazin 3 yl ) pyridine arrangement (BTP Figure 3 1 ) revealed by Kolarik to have separation factors (SF = D x /D y where x and y are two metals extracted under the same conditions and D refers to the distribution ratio defined by D = [M] aque ous /[M] organic which are the metal concentration in the two phases after a biphasic extraction) in the range of 120 130 for Am over Eu from 1M nitric acid aqueous solutions. 14, 15 This select ivity for Am over Eu is on the range of an order of magnitude greater than other similar terdentate ligands like terpyridine 62 and bis ( 1,3,5 tri a zin 3 yl ) pyridines 63 It was shown that 3 1 binds smaller Ln (Sm Lu) in a 3:1 ratio un common for nitrogen donor ligands when in competition with nitrates and water. 27, 64 More common for terdentate hete rocyclic N donor ligands is the 1 :1 binding mode with nitrates and water molecules filling the remainder of the inner coordination sphere ; 65 h owever it was also shown that larger Ln (L a Pm) bind with various com binations of compound 3 1 again with nitrate anions, and water molecule filling the rest of the coordination sphere. 66, 67 3 1 .1 Evidence of Bis (1,2,4 triazine)Pyridine selectivity Th e amazing preference of BTP ligands for U over Ce was exhibited in work by Iveson et al. 64 In a 1:1 solution of UI 3 and Ce I 3 was added from 1 to 3 equivalents of either the methyl or isopropyl derivative of BTP. The only species present by 1 H NMR

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57 was the U(BTP) 3 3+ complex. With an excess of BTP beyond three equivalents the formation of Ce(BTP) n 3+ n = 1 3, was observed Similar experiments were performed with common terdentate ligands but none showed similar c omplexation behavior. 68, 69 3 1.2 Radiolytic and Hydrolytic Degradations of N Donor Extractants The environment under which extractions of this type are performed is unique in its s tresses. Not only is there a significant strain on organic substituents towards hydrolysis by the high concentration of nitric acid and its nitrous acid degradation product 70 but also the large quantity of high en ergy particles and gamma rays. The mechanism of radiolytic degradation is thought to include free solvated electrons. 71, 72 Transition metal complexes with 3 1 and 3 2 are known to have divers e electrochemical properties but in those cases ligand stability is an issue once the complexes are reduced 73 3 1.2A Degradation of BTP I n ex traction tests of 3 1 with an actual effluent of the DIAMEX process at the Atalante facility in Marcoule, France an issue arose due to degradation of the ligand under the extraction experiment conditions. 74 Research efforts shifted into determining the position of degradation to des ign more robust ligands. It was shown that the protons in the position relative to the 5 and 6 positions (refer to Figure 3 1) of the triazine rings was the location where radiolytic oxidative damage was concentrated (Figure 3 2) 72, 74 Ligand design shifted into molecules omitting protons in the positions to examine the effect on ligand stability Two compounds recently reported contain annulated rings cyclizing the 5 and 6 position of the triazine rings. These modifications

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58 caused a marked increase in the stability of 3 3 and 3 4 relative to 3 1 and 3 2. Compound 3 4 showed no degradation after dissolution in boiling nitric acid over 24 hours and after exposure to a 100kGy dose of radiat ion in 1 octanol. 75 3 1.2B Degradation of BTBP bis(5,6 dialkyl 1,2,4 triazin 3 yl) bipyridine (BTBP Figure 2 2 ) is an extractant that has been studied extensively in the literature as a ligand for u se in the selective actinide extraction process (SANEX) It is structurally similar to the BTP ligands. Work performed by Zorz and coworkers 76 aimed at elucidating the breakdown products of BT BP by radiolysis was p erformed with APCI MS. The point of degradation of the ligand was always at the position to the triazine rings as previously shown for BTP as well. Most breakdown products contained oxidative degradat ion as either ketones or hydroxyl groups in the positions. None of the identified products were altered at the pyridine rings or t he triazine rings. 77 3 2 Results and Discussion 3 2.1 2,6 Bis 1,2,4 Triazin 3 yl Pyridine Based Extractants The initial target ligand (Figure 3 4 ) was an attempt to include three BTP binding units into one nonadenta te ligand. Base d on previous results this donor group should modify the selectivity while increasing the extraction performance. It should also slow the kinetics of metallation. The initial step (i, Figure 3 4) was a combination of two synthetic steps. The y were ac complished using phosphorous oxy chloride (POCl 3 ), isolation of th e compound and then condensation with hydrazine to form the 2,6 (carbohydrazonamide) pyridine 3 6 according to literature procedures. 78, 79 The second step (ii, Figure 3 4) entailed a bis(5 phenyl 1,2,4 triazin

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59 3 yl)pyridine 3 7 a or with benzil to afford 2,6 bis(5,6 phenyl 1,2,4 triazin 3 yl)pyridine 3 7 b both in high yield. Though there was the chance for isomerization in the reaction to generate 3 7 a the increased reactivity of the aldehyde group of the phenyl glyoxal dictated formation of only one isomer accordi ng to examination of the NMR spectrum of the pure compound. There was no evidence of other peaks or shouldering that would be indicative of a small structural change. There are other reports in the literature of similar reactions with phenyl glyoxal yielding an isomer excess of 34:1 80 The third step in the synthetic scheme (iii, Figure 3 4) involved an oxidation of 3 7 a that would theoretically induce reactivity in the triazine ring 6 position allowing for nucleophilic attack. 81 Attempts with meta chloroperoxybenzoic acid and hydrogen peroxide with different stoichiometries and reaction times always led to mixtures of oxidized products. Mass spectral analysis indicated formation of the singly and doubly oxi d ized derivative. T he mixture of oxidized BTP was reacted with trimethylsilylcyanide but no reaction was detected. This result effectively closed the potential for this route and other ideas were entertained. 3 2.2 6 (5,6 diphenyl 1,2,4 Triazine 3 yl ) Pico linamide Based Extractants Design efforts shifted into ligands with more verifiable synthetic schemes from the literature. The procedure focused on 6 ( 5,6 diphenyl 1,2,4 triazin 3 yl)picolinamide based extractants tethering the donors to the triphenoxymet hane scaffold through a carboxylic acid group on the donor set and an amine group of the triphenoxymethane (Figure 3 5) This design still implemented a 1,2,4 triazine and theoretically should have extraction selectivity similar to BTP The proposed arc hitecture also included a n amide

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60 carbonyl oxygen as a donor and with the hard acid characteristics of the Ln and An should generate a strong coordinating ligand 3 2.2A Synthesis of (5,6 Diphenyl 1, 2,4 triazin 3 yl) picolinamide ligands i ncorporating the triphenoxymethane p latform The synthesis shown in Figure 3 6 began with 6 methylpicolinitrile being condensed with hydrazine which results in 3 9 in 88% yield. 79 Step ii and v contained a n with diphenyl dione in ii and 3,4 he xanedione in v with both reactions affording yields greater than 90%. 75 Step iii entailed an oxidation of 3 10 that was performed with selenium dioxide to form the aldehyde derivative 3 11 which was not isolated because the largest contributing impurity was the over oxidized carboxylic acid 3 12. 82 The parallel reaction to generate 3 14 showed complete degradation of the starting mate rial 3 13 and it is believed this was due to preferential oxidation of the carbons in the position to the triazine rings as discussed previously. Step iv entailed a second oxidation with silver nitrate and sodium hydroxide to generate 3 12 in 80% yield over steps iii and iv. 83 Starting from 3 12 mult iple ligands were synthesized to modulate the solubility of the ligand in organic solvents and the flexibility of the binding pocket. Figure 3 7 shows the methods followed to generate all ligands compared in this work. In each case 3 12 was initially co nverted in to the acyl chloride derivative by reaction with thionyl chloride. Afte r isolation of 3 12 Acyl (assumed quantitative), it was combined with the tris amine triphenoxymethane or dialkylamine with dimethylaminopyridine as base and catalyst. 3 15 t o 3 19 were isolated in yields ranging from 65% to 76% in high purity. Another terdentate BTP derivative, 2,6 bis(5,6 diphe nyl 1,2,4 triazin 3 yl)pyridine ( 3 7 b ) was synthesized according to literature procedures. 84 This compound was

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61 synthesized for a tangible comparison of laboratory methods to those reported in the literature for solid state structures and extraction experiments. 3 2.2B Hydrolytic degradation i nvestigation Given the known susceptibility of 1,2,4 triazines to hydrolytic degradation it was necessary that experiments be carried out to determine the robustness of synthesized ligands in r ealistic conditions No literature report was found performing a degradation analysis on diphenyl 1,2,4 tria zine Ligand 3 19 was dissolved in a 2mL portion of CD 2 Cl 2 an d contacted with a 2mL sample of 1M HNO 3 in a scintillation vial. The vial was placed on a shaker table for 24 hours. The layers were allowed to separate for 2 hours as is normal for extract ion experiments the organics were separated, and then the 1 H NMR spectrum was collected The comparison of the spectrum before the contact and after is shown in Figure 3 8. The only deviation that was observed was a broad triplet centered at 9.28ppm whi ch was assigned to the amide N H There is a shift of 0.20ppm which was deemed negligible and most likely a n artifact of protonation of the pyridine ring in the absence of metal ion. It was assumed that 3 17 and 3 18 would show the same robustness as no degradation at the alkyl groups of the triphenoxymethane platform has ever been observed. 3 2.2C Solid S tate s tructure c omparison of ML and ML 3 c omplexes with La, Eu, Er, and Yb In an effort to determine the quality of match between the ideal trigonal tric apped prismatic geometry found for Ln and An in solution X ray diffraction quality crystals were grown of different metal complexes for comparison. The metal complexes were synthesized by mixing of the appropriate metal salt with the corresponding ligand in ethyl acetate The chosen ligand was combined with

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62 an excess of metal salt which commonly generated off white precipitates within a short period of time. Diffusion crystallizations were then prepared based upon the solubility of the resulting complex The chosen metal was added in excess to allow the system to find its thermodynamic sink. For example if the bimetallic complex was more stable with the donor arms splayed out or perhaps dimerization. Figure 3 9 shows a common orientation upon crystal lization of complexes. With many nitrate complexes the anion was a metal ion coordinating all or most of the necessary nitrates for charge balance. The structures derived from the triflate salts did not show this behavior and instead had three triflate counter anions in the asymmetric unit The analysis centered on bond lengths and the twist within the prism of the trigonal tricapped prismatic geometry away from 0 or ideal. This was done by determining the plane made by the upper and lower donors tha t defined the faces of the trigonal prism. In La 2 (3 17)( NO 3 ) 6 the upper face is defined by three N Triazine donors and the lower face by the three carbonyl O donors. The center of gravity of each plane was calculated by averaging the coordinates of the at oms at the vertices of the plane. This used as reference points for determining the dihedral angle of each pair of related vertices of the prism and the three measured angles were averaged Complexes were made with 3 17 and La, Er, and Yb to explore the changes that occur with differing ionic radius. The salt varies from nitrate to triflate in these structures but no deviation was seen with changing anion which was expected as the anion is in all cases excluded from the coordination sphere of the metal The structure results are summarized in Table 3 1. La(3 17) has the longest bond lengths and the largest twist

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63 angle. Interestingly the decrease going from La to Er is not proportional to the decrease in the ionic radii for the M N Triazi ne or the M N Pyridine The M O bond decreases less than expected which may imply that La is showing greater attraction of the hard oxygen donor but more likely this is an artifact of increased strain in the donor arm of coordination of La compared to coor dination of smaller Er The decrease from Er to Yb which are close in the Ln series is proportional to the decrease in the ionic radii. The impact of differing alkyl steric bulk in the ortho position relative to the phenolic oxygen in the triphenoxyme thane platform was also investigated. Multiple complexes were determined all with Yb as this metal was shown to have the closest match to ideal trigonal tricapped prismatic geometry. Table 3 2 compares the Yb(3 17), Yb(3 18), and Yb(3 19) structures. Cle arly alkyl substitution in the ortho position of the triphenoxymethane scaffold impacts the binding pocket with modest modification of the twist angle The bond lengths are not substantially impacted. Increasing steric bulk in that position strains the donor arms away from 0 and t his allows for design of ligands with manipulation of the geometric match of ligand to metal. The terdentate deri vatives synthesized (3 7 a 3 7 b and 3 16) were also crystallized in a similar manner to previously discussed comp ounds. 3 7 a and 3 7 b were used as parallels of the many literature structures. The bond lengths in the terdentate picolinamide (3 16) and the triphenoxymethane tethered picolinamide (3 17) are compared to the BTP derivatives (3 7 a 3 7 b ) in Table 3 3. Th e Yb(3 16) 3 3+ complex showed a similar M N Triazine bond length to Yb(3 7 b ) 3 3+ which was encouraging as it was thought that the short M O bond in Yb(3 16) 3 3+ would

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64 distort the M N Triazine bond by lengthening it and possibly removing the finer bonding struct ure that the triazine ring is known to exhibit. Yb(3 7 a ) 3 3+ possesses shorter M N Triazine bonds than Yb(3 7 b ) 3 3+ because t he 6 position of the triazine ring s in 3 7 a are occupied by a hydrogen and in 3 7 b the 6 position s are occupied by a phenyl group. A ll terdentate derivatives had shorter M N Triazine bond lengths than the nonadentate picolinamide 3 17. T ethering all donors to one plat form does increase stability by the chelate effect but when the scaffold has limited flexibility by design there is also a degree of freedom constriction which can imbue selectivity by destabilizing certain metal complexes because the ligand cannot orient the donors in the ideal positions 3 2.2D Metallation r ate s tudies A necessary property for industrial applications of biphasic extractants is fast kinetics of metallation. This is a major constraint as novel ligands become more organized as compared to mono or bidentate analogues The rates of metallation of 3 19 were measured using UV/VIS spectroscopy and pseudo fi rst order kinetics conditions. Compound 3 19 was expected to have the slowest kinetics because it was nonadentate but it also had the largest amount of steric hindrance with the ligand arms according to the solid state analysis. The experiment was performed b y adding spikes of large excess Yb(NO 3 ) 3 concentration relative to the ligand (approximately 15:1, 30:1, 50:1, and 65:1) mixing for approximately three seconds and then measuring the UV/VIS spectrum at pre determined intervals. Initially the experiments w ere run in acetonitrile but given the experimental conditions this was not possible as equilibrium was reached in an interval of time shorter than the three second mixing time. Useful data was collected from experiments in tetrahydrofuran as it is a stron ger coordinating solvent and therefore

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65 slowed the reaction rates to measureable levels Methanol is the most common solvent in the literature for these types of experiments but due to extremely limited solubility of the ligand in methanol this solvent was not used 53 A collection of s pectra are shown in Figure 3 11 ( left ) for the 50:1 addition highlighting the change over time for the expected metallation reaction defined in Equation 1 On the right of Figur e 3 11 is a plot of the change at = 305nm which was the wavelength with the largest change over time and used in all analysis Each metal to ligand ratio was measured in triplicate and an example of a pseudo first order plot is depicted in Figure 3 12 Each set of spectra was treated according to Equations 2 from which k obs was extracted as the slope of the plot of ln(A A t ) versus time The linearity of the se plots indicates that the metallation reaction is pseudo first order This is also indicate d by the clear isobestic points. The results of the kinetic analysis are collected in Table 3 4 for 3 19 and all metal solution additions. 53 The rate constant for the reaction (k) was determined as the slop e of the plot of k obs versus [M 3+ ] according to Equation 3 M (NO 3 ) 3 + L [ ML ](NO 3 ) 3 (1) (2) (3) 3 2.2E Binding c onstant s tudies The binding constant K defined as K = [ML] 3+ /[M] 3+ [L] for the reaction M 3+ + L = ML 3+ is a necessary descriptor when analyzing the quality of an extractant. Though extraction of metals across a phase boundary is a complex process high strength

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66 coordination is always a necessity. Binding constants were determined using UV/VIS spectroscopy in acetonitrile to ensure fast equilibra tion. Ligands were typically dissolved in 3mL of acetonitrile at a concentration of approximately 2 x 10 5 M. Addition volumes were varied depending on metal titrant solution concentration to achieve a 1 to 1 M:L ratio at approximately 10 additions. Dep ending on the binding strength more additions may have been necessary. The results of these experiments are summarized in Table 3 5. There was little difference between Eu and Yb which is in line with the extraction results. La showed by far the smallest binding constant again in line with extraction results. T he results of these experiments while in conditions different from the extraction conditions are a useful guide to determining extractant effectiveness 3 2.2F Extraction efficiency s tudie s The f undamental goal of all ligand design schemes is efficient extraction. Due to the limit ed access to An because of their inherent hazard extractions were performed with a select group of Ln. In all cases equal volumes of an organic phase containing the lig and was contacted with a 1M nitric acid aqueous solution of the chosen metal at 1 x 10 4 M. Commonly the ligand was tested at a 10:1 molar ratio for L:M but was at times increased to determine the effect of a larger quantity of ligand on the extraction eff iciency. The organic phase was either dichloromethane or 1 octanol. Extractions were performed with 3 17, 3 18, and 3 19 to examine the effect of the alkyl substitution which most directly affects the organic layer solubility. It was shown that across the group of metals tested that the selectivity towards the heavier, smaller Ln and that the efficiency increases as the steric bulk increases. This was seen with the solubility of metal complexes synthesized and tested as complexes of 3 19 had

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67 significan t solubility in a larger number of solvents while complexes of 3 17 were only soluble in highly polar solvents like methanol. Extractions using COSAN were performed with 3 19 in similar conditions to those described in Chapter 2. The solvent for the COS AN extraction was again dichloroethane while the extraction with out COSAN was performed in dichloromethane. The results are depicted in Figure 3 15 showing similar affect of COSAN on the extraction system as was seen with 2 6 b The COSAN additive had an antagonistic effect on the system and further experiments are necessary to determine if COSAN can be synergistic for extraction efficiency and if so the optimal concentration. 3 2.3 6 (5,6 diphenyl 1,2,4 triazin 3 yl)diisobutyl Picolinamide Analogue 1 H NMR spectroscopy was used to determine the solution state structure of 3 16 in acetone. It was thought it would be an adequate analogue of 3 17 to 3 19. Lu(NO 3 ) 3 ( H 2 O) was added in sequential doses and the spectrum recorded. Lu was chosen due to its diamag netism and the expected strong coordination due to the strong interaction of 3 19 to Yb 3+ The spectra are represented in Figure 3 16 with the free ligand the bottom most spectrum and ascending each successive spectrum represent ing the 1:6, 1:3, 1:2, and 1:1 metal to ligand ratios respectively. Upon metallation deviation is seen from the free ligand but the spectrum for the products did not indicate formation of a single complex at any metal to ligand ratio Even at the 1:1 metal to ligand ratio the pea ks are indiscernible indicating a mixture of species present in the solution. In literature experiments to determine solution state structure combinations of complexes are always seen with varying ligation (ML 3 ML 2 M 2 L 2 etc). 66, 85, 86

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68 After the titration was completed the NMR sample was left sitting and crystallization occurred. A significant amount of crystals formed relative to the starting quantity of 3 1 6 with a uniform crystalline morphology. Crystal samples were removed for X ray diffraction analysis but the crystal quality was insufficient to collect diffraction data. A second sample was taken, dried under reduced pressure, and the 1 H NMR spectrum ta ken and the results being very similar to the spectrum for the 1:1 metal to ligand ration solution. This seems to indicate that that the complex attaints a standard equilibrium upon dissolution but the crystals represent the most stable complex. Elementa l analysis was performed on a sample indicating the most likely structure in the crystal being Lu(3 16)(NO 3 ) 3 S with S being an acetone d 6 molecule. The inability of this ligand to bind in a preferential 1:3 ratio parallels the result with Bis ( 5,6 diiso propyl 1,2,4 triazin 3 yl)pyridine with Ce. 28, 69 3 3 Conclusions A new family of ligands containing a combination of pyridine, 1,2,4 triazine, and amide carbonyl oxygen donors has been synthesized. These ligands show some selectivity for the heavier, smaller Ln but the extraction efficiency did not exceed 35% after one contact for any metal with any derivative at the 10:1 ligand to metal ratio. T he ligand design is based on liter ature examples of donors for selective An extraction so substantial Ln extraction was not expected Selectivity is always paramount because poor efficiency can be overcome by repeated contacts. The highest extraction was shown by 3 19 with the largest a lkyl groups in the ortho positions of the triphenoxymeth ane platform. This alkyl group distort s the binding pocket to the largest degree according to the twist angle yet this ligand was the most efficient extractant for all Ln tested. The extraction perf ormance seems to be

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69 determined more by solubility of the ML complex in the organic phase than small deviations from the ideal trigonal tricapped prismatic geometry between the ligands.

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70 3 4 Experimental 3 4.1 General Considerations 1 H and 13 C NMR spectra were recorded on a Gemini300, Varian300, or Mercury300 NMR instrument at 299.99 MHz for the proton channel and 75.47 MHz for the carbon channel. All UV/ VIS spectra were recorded on a Varian Cary 50 spectrophotometer E ach sample analyzed by mass spectro metry was dissolved in appropriate solvent and underwent direct injection through an autosampler, followed by ESI or APCI analysis with methanol (with or without 0.2% acetic acid ) as mobile phase. For MALDI, the solution was usually added onto the matrix s pot of dithranol, cyano 4 hydroxycinnamic acid, dihydroxybenzoicacid or terthiophene. Solvent was used only when necessary for DART. The ions were detected with the Agilent 6210 TOF MS while the data was Elementa l analyses were performed at the in house facilities at the University of Florida. All solvents unless otherwise noted were used as received and either HPLC or ACS grade. Metal nitrate salts were purchased from Sigma Aldrich. They were dried under vacuu m but otherwise used as received. Metal solutions were made using 18 Millipore deionized water and TraceMetal grade HNO 3 (Fisher Scientific). Arsenazo(III) dye was used as a UV/VIS sensitizer for all metal extraction experiments. Pyridine 2,6 bis(carbohy drazonamide) 78, 79 was synthesized according to literature procedures as was compound 3 7 b 84 3 4.2 Binding Constant and Kinetics UV/VIS Experimenta l Conditions For all UV/VIS experiments a quartz cuvette with a 1cm path length was used along with dry, deoxygenated acetonitrile or THF to allow for analysis down to = 240nm. 3mL of the ligand solution at approximately 7 x 10 5 M were pipetted into the cuvette

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71 using an automatic pipettor. The background consisted of tetrabutylammonium nitrate ( [ N Bu 4 ]( NO 3 ) ) at a concentration of 1 x 10 2 M to ensure that the ionic str ength was constant throughout. For the kinetics measurements pseudo first order conditions were used. The Yb solution concentration was 2.10 x 10 2 M. The spike volume was adjusted to generate M:L ratios of approximately 15 to1, 30 to 1, 50 to 1, and 6 5 to 1. The spike was administered with an automatic pipettor and the solution was pipette back and forth three times with a glass pipette for mixing which lasted 2 to 3 seconds. The spectra were then collected at a gradient time scale for 80 minutes. Fo r the binding constant experiments the free ligand spectrum was collected followed by addition of a spike of metal solution with a concentration approximately 2 x 10 3 M. The spike volume was chosen to added a 1:10 molar ratio M:L for each spike. The solu tion was then stirred for 5 minutes and the spectrum collected. This was repeated until the system reached equilibrium. The data was processed using Reactlab EQUILIBRIA created by Jplus Consulting. This global analysis software fits the UV/VIS spectral trends and outputs the binding constant. 3 4.3 Metal Extraction Experiments The procedure for metal extraction experiments followed a previous literature report. 58 4mL solutions of the ligand in the chosen orga nic solvent were contacted with 4mL of the 1M nitric acid aqueous phase containing the metal at 1 x 10 4 M in 20mL borosilicate scintillation vials with plastic cone lined urea caps (Fisher Scientific). Each metal was tested in triplicate. The vials were sealed and contacted for 24 hours on a shaker table. The vials were then allowed 2 hours for phase separation. 1mL aliquots of the aqueous phase were then extracted with an automatic pipettor and placed in

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72 25mL volumetric flasks and diluted to the mark w ith formic acid/sodium formate with 2.5mL of the Arsenazo(III) dye added. The UV/VIS spectrum of each metal was collected at = 655nm. The result was compared against the spectrum of the sampled metal solution with no extraction according to the formula: E% = 100*[(A 1 A)/(A 1 A 0 )] where A is the absorbance of the extracted aqueous phase, A 1 is the absorbance of the unextracted metal solution, and A 0 is the absorbance of the metal free nitric acid solution diluted in the buffer. Another descriptor was the distribution rations calculated by the following equation: D= [M org ]/ [M aq ]. [M org ] is the concentration of the metal in t he organic phase and [M aq ] is the corresponding concentration of the remaining metal in the aqueous phase. As these two quantities were not both measured the equation used to determine D was based on the extraction efficiency: D = E%/(100 E%). The final descriptor used was the separation factor which is a measure of the selectivity of a ligand for one metal as compared to another metal under the same extraction conditions and this is calculated by: SF m/n = D m /D n 3 4.4 Synthetic Procedures 3 4.4 A Compound 3 7a Phenyl glyoxal (3.31g, 21.7mmol) was dissolved in 50mL of a 4:1 mixture of ethanol:water. 3 6 (1.91g, 9.89mmol) was also dissolved in 4:1 ethanol:water and placed in an addition funnel. The solution of 3 6 was added slowly and the reaction then sti rred for three days during which time a yellow precipitate formed. This precipitate was collected by fi ltration under reduced pressure to yield 3 7a as a bright yellow solid (3.80g, 99%). 1 H NMR (CHLOROFORM d ) ppm 7.52 7.70 (m, 6 H),

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73 8.21 (t, J =7.9 Hz, 1 H), 8.37 8.44 (m, 4 H), 8.88 (d, J =7.7 Hz, 2 H), 9.77 (d, J =0.3 Hz, 2 H). 13 C { 1 H} NMR 125.8, 127.9, 129.3, 132.7, 133.2, 138.3, 145.2, 153.6, 155.7, 162.5. Anal. calcd. for C 23 H 15 N 7 : C, 70.94; H, 3. 88; N, 25.18. Found: C, 68.25; H, 4.12; N, 24.42. 3 4.4 B Compound 3 9 6 methylpicolonitrile (4.05g, 34.3mmol) was added to a flask with 65% hydrazine aqueous solution (65mL) and heated to 70 C for 4 hours during which time all the 6 methylpicolonitrile di ssolved. The solution was cooled to room temperature and then placed in a refrigerator overnight. The resulting crystals were collected by filtration and dried under reduced pressure to yield 3 1 as white crystals (4.28g, 83%). 1 H NMR (CHLOROFORM d ) ppm 2.53 (s, 3 H), 3.97 (br. s., 2 H), 5.37 (br. s., 2 H), 7.10 (d, J =7.4 Hz, 1 H), 7.55 (t, J =7.8 Hz, 1 H), 7.79 (d, J =7.9 Hz, 1 H) 13 C { 1 H} NMR 24.2, 116.5, 123.2, 136.6, 149.0, 149.8, 156.7 HRMS ESI: calcd for [M+H] + : m/z 151.0907. Found: m/z 151.0978. Anal. calcd. for C 7 H 10 N 4 : C, 55.98; H, 6.71; N, 37.31. Found: C, 55.65; H, 6.92; N, 37.54. 3 4.4 C Compound 3 10 Compound 3 9 (1.50g, 10.0mmol) was combined with benzil (2.10g, 10.0mmol) in 150mL of ethanol. The mixture was heated to reflux fo r 4 hours before cooling to room temperature. The solvent was removed under reduced pressure and the residue was recrystallized from isopropanol to yield 3 10 as yellow crystals ( 3.08g 95%). 1 H NMR (CHLOROFORM d ) ppm 2.76 (s, 3 H), 7.30 7.48 (m, 7 H), 7.60 7.74 (m, 4 H), 7.80 (t, J =7.8 Hz, 1 H), 8.47 (d, J =7.6 Hz, 1 H). 13 C { 1 H} NMR ppm 24.83 121.31 125. 14, 128.44, 128.54 129.4 8, 129.93, 130.65, 135.33, 135.63 137.0 7, 152.31, 155.94

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74 156.1 8, 159.40, 160.83 HRMS ESI: calcd for [M+H] + : m/z 325.1448 ; [2M+H] + : m/z 649.2828; [3M+H] + : m/z 973.4203 Found: m/z 325.1433 649.2828, 973.4179 Anal. calcd. for C 21 H 16 N 4 : C, 77.76; H, 4.97; N, 17.27. Found: C, 77.50; H, 4.9 4; N, 17.36. 3 4.4 D Compound 3 11 Co mpound 3 10 ( 5.31g, 16.4mmol) was added to 175mL of 1,4 dioxane and selenium dioxide (9.1g, 81mmol) was added to the reaction vessel which was then heated to reflux overnight. The reaction was cooled to room temperature and placed in the refrigerator for 1 hour. Solid impurities were removed by filtration on a Buchner funnel and the solvent was removed under reduced pressure. The residue was dissolved in hot DMSO (100 C) until completely dissolved and the solution was cooled to room temperature. Cold wa ter was added which caused 3 11 to precipitate as a pale yellow solid. The mixture was placed in the refrigerator for 2 additional hours and the resulting precipitate was collected by filtration and used without further purification. The main by side pro duct was the overoxidized compound 3 12 and further purification would reduce the overall yield of 3 12 1 H NMR (CHLOROFORM d ) ppm 7.32 7.51 (m, 6 H), 7.68 (dd, J =16.8, 6.9 Hz, 4 H), 8.08 8.20 (m, 2 H), 8.91 (dd, J =6.9, 1.6 Hz, 1 H), 10.33 (s, 1 H). 13 C { 1 H} NMR ppm 122.85, 128.02, 128.61, 128.65 129.5 1 1 29.89, 129.94, 130.99, 134.96, 135.29 1 38.24, 153.21, 153.43, 156.29, 156.76 159.8 1 193.3 3 3 4.4 E Compound 3 12 A slurry was made by the addition of the residue of 3 3 to 175mL of acetonit rile. Silver nitrate (13.9g, 81mmol) was dissolved in water (30mL) and added to the reaction mixture at which point all 3 3 dissolved. Solid sodium hydroxide (4.9g, 121mmol) was

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75 added and the resulting black solution stirred for 2 days. The pH of the sol ution was adjusted to approximately 3 by addition of 10% HCl solution. Dichloromethane was added (100mL) and both layers were filtered over a Buchner funnel. The organic layer was separated and the aqueous layer was extracted with dichloromethane (50mL) two times. The combined organics were washed with brine. The solvent was dried with magnesium sulfate and the solvent removed under reduced pressure. The residue was stirred in a small amount of refluxing methanol which was then allowed to cool to room temperature. The resulting mixture was passed over a fritted filter to yield 3 12 as a pale yellow solid (4.80g, 83% over two steps 1 H NMR (CHLOROFORM d ) ppm 3.28 3.61 (m, 3 H), 7.34 7.54 (m, 6 H), 7.57 7.72 (m, 4 H), 8.14 (t, J =7.8 Hz, 1 H), 8.41 (d, J =7.6 Hz, 1 H), 8.88 (d, J =7.9 Hz, 1 H). 13 C { 1 H} NMR ppm 126.30, 126.97, 128.69, 129.47, 129.75, 130.13, 131.24, 134.57, 134.86, 139.12, 147.86, 151.01, 156.59, 157.10, 159.04, 165.19. HRMS ESI: calcd for [MH] + : m/z 355.1190. Found: m/z 355.1206 Anal. calcd. for C 22 H 18 N 4 O 3 : C, 68.38; H, 4.70; N, 14.50. Found: C, 68.21; H, 4.53; N, 14.66. 3 4.4 F Compound 3 15 A 0.51g portion of 3 12 ( 1.4mmol) was combined with thionyl chloride (2.1mL, 29mmol) in 50mL of chloroform and heated to reflux for 3 hours. T he solvent was removed under reduced pressure to removed residual thionyl chloride. The residue was dissolved in 50mL of fresh chloroform and coo led to 0 C. Triethylamine (0.60mL, 4.3mmol and diisopropylamine (0.61mL, 4.3mmol) were then injected into the reaction vessel. The solution was warmed to room temperature and stirred overnight. The reaction mixture was extracted with 10% HCl solution (2 5mL) three times followed by

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76 1M NaOH (25mL) and brine (25mL). The organics were dried with sodium sulfate and removed under reduced pressure. The residue was recrystallized from methanol to yield yellow crystals of 3 15 (0. 44g, 70%). 1 H NMR (CHLOROFORM d ) ppm 1.32 (d, J =6.6 Hz, 6 H), 1.59 (d, J =6.9 Hz, 6 H), 3.63 (spt, J =6.8 Hz, 1 H), 4.27 (spt, J =6.6 Hz, 1 H), 7.29 7.47 (m, 6 H), 7.60 7.72 (m, 4 H), 7.78 (dd, J =7.7, 1.0 Hz, 1 H), 8.00 (t, J =7.8 Hz, 1 H), 8.68 (dd, J =7.9, 0.9 Hz, 1 H) 13 C { 1 H} NM R 20.5, 20.9, 46.2, 50.9, 77.2, 124.2, 124.9, 128.3, 128.5, 129.4, 129.7, 129.8, 130.7, 135.2, 135.4, 137.9, 151.1, 155.9, 156.1, 156.6, 160.5, 167.8. 3 4.4 G Compound 3 16 A 0.75g portion of 3 12 ( 2.1mmol) was combined with thionyl chloride (3.1mL, 42m mol) in 100mL of chloroform and heated to reflux for 3 hours. Then the solvent was removed under reduced pressure to removed residual thionyl chloride. The residue was dissolved in 100mL of fresh chloroform and cooled to 0 C. Dimethylaminopyridine (1.3g 10.5mmol) was added and then diisobutylamine (1.10mL, 6.3mmol). The solution was warmed to room temperature and stirred overnight. The solvent was washed with 10% HCl solution (40mL) three times followed by 1M NaOH (40mL) and brine (40mL). The organic s were dried with sodium sulfate and removed under reduced pressure. The residue was recrystallized from ethanol to yield yellow crystals of 3 16 ( 0.73g, 74%). 1 H NMR (CHLOROFORM d ) ppm 0.77 (d, J =6.5 Hz, 6 H), 1.03 (d, J =6.8 Hz, 6 H), 1.88 (spt, J =7.1 Hz, 1 H), 2.21 (spt, J =6.5 Hz, 1 H), 3.44 (d, J =7.6 Hz, 2 H), 3.63 (d, J =7.6 Hz, 2 H), 7.30 7.50 (m, 6 H), 7.61 7.74 (m, 4 H), 7.82 7.89 (m, 1 H), 8.00 (t, J =7.9 Hz, 1 H), 8.67 (dd, J =7.8, 1.0 Hz, 1 H) 13 C { 1 H} NMR 19.9, 20.3, 26.7, 27.9, 53.8 56.4, 124.3, 125.7, 128.4, 128.7, 129.5, 129.8, 130.0, 130.9, 135.3, 135.5, 137.8,

PAGE 77

77 151.1, 155.8, 156.2, 160.4, 168.6 HRMS ESI: calcd for [M+H] + : m/z 466.2601. Found: m/z 466.2597. Anal. calcd. for C 29 H 31 N 5 O: C, 74.81; H, 6 .71; N, 15.04. Found: C, 74 .50; H, 6.74 ; N, 15.06 3 4.4 H Compound 3 17 A sample of 3 12 (1.51g, 4.3 mmol) and thionyl chloride ( 6.2mL, 85 mmol) were added to 100mL of chloroform and the mixture was heated to reflux for 2 hours. The solvent was removed under reduced pressure to affor d the crud e acid chloride. This material was dissolved in 100mL of fresh chloroform and cooled to 0 C. A 0.60 g portion of 2 3a ( 0.95 mmol) and 2.32 g of 4 dimethylaminopyridine ( 19 mmol) were dissolved in a small amount of chloroform and injected into the reaction vessel drop wise. The reaction was then allowed to warm to room temperature and stirred overnight. The organic phase was washed with 40mL of 10% HCl solution three times followed by washing with 1M NaOH. The organics were dried with sodium sulf ate and allowed to sit on the bench top for 1 hour, resulting in precipitation of Na + 3 12 The precipitate was removed by filtration along with the drying agent. The organics were then removed under reduced pressure. The final purification was accompli shed by silica gel column chromatography using 1:4:1 dichloromethane:tetrahydrofuran:hexanes afforded 3 17 as a pale yellow solid (1.43g, 91%) 1 H NMR (CHLOROFORM d ) ppm 1.06 1.31 (m, 27 H), 2.17 (s, 9 H), 3.61 3.71 (m, 6 H), 3.76 (br. q, J =5.0, 5.0, 5.0 Hz, 6 H), 6.92 (s, 3 H), 6.98 7.14 (m, 10 H), 7.21 7.43 (m, 15 H), 7.45 7.58 (m, 12 H), 7.78 (t, J =7.8 Hz, 3 H), 8.09 (d, J =7.9 Hz, 3 H), 8.41 (d, J =7.9 Hz 3 H), 9.09 (t, J =5.6 Hz, 3 H) 13 C { 1 H} NMR 17.0, 31.4, 34.2, 40.1, 71.0, 123.6, 125.5, 125.7, 126.1, 128.3, 128.5, 129.5, 129.6, 129.8, 130.3, 130.6, 135.2, 135.2, 136.4, 137.8, 145.5, 150.9, 151.2, 152.8,

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78 155.7, 156.1, 159.7, 164.1. HRMS ESI: cal cd for [M+H +K ] + : m/z 840.3741 Found: m/z 840.3719 3 4.4 I Compound 3 1 8 A sample of 3 12 (1.55g, 4.37mmol) and thionyl chloride (3.17mL, 44mmol) were combined in 100 mL of chloroform and heated to reflux for 2 hours. The solvent was removed under reduced pressure to afford the crude acid chloride. The residue was dissolved in 100 mL of chloroform and cooled to 0 o C. A 0.74g portion of 2 3 b (0.97mmol) and 2.38g of 4 dimethylaminopyridine ( 19.4mmol) were dissolved in a small amount of chloroform and inject ed into the re action vessel drop wise. The reaction was then allowed to warm to room temperature and stirred overnight. The organic phase was washed with 40 mL of 10% HCl three times followed by washing with 40 mL of 1M NaOH three times. The organics wer e dried with sodium sulfate and allowed to sit on the bench top for 1 hour resulting in precipitation of reformed Na + 3 12 The precipitate was removed by filtration along with the drying agent. The organics were then removed under reduced pressure. F inal purification was accomplished by passing the residue over a plug of silica gel and removal of solvents under reduced pressure affording 3 1 8 as a pale yellow solid (1.19g, 67%). 1 H NMR (CHLOROFORM d ) ppm 1.19 (s, 27 H), 1.26 (s, 27 H), 3.74 3.86 (m, 6 H), 3.90 4.08 (m, 6 H), 6.59 6.63 (m, 1 H), 7.15 (dd, J =9.6, 2.0 Hz, 6 H), 7.22 7.42 (m, 18 H), 7.50 (d, J =7.4 Hz, 6 H), 7.57 (d, J =7.6 Hz, 6 H), 7.84 (t, J =7.8 Hz, 3 H), 8.27 (d, J =7.6 Hz, 3 H), 8.54 (d, J =7.6 Hz, 3 H), 9.00 (t, J =5.9 Hz, 3 H) 13 C { 1 H} NMR 31.3, 31.5, 34.4, 35.4, 40.2, 67.9, 122.2, 123.8, 126.0, 126.8, 128.4, 129.5, 129.6, 129.9, 130.7, 135.1, 135.4, 137.7, 137.9, 141.9, 144.4,

PAGE 79

79 150.9, 151.5, 153.3, 155.9, 156.1, 160.2, 164.3 Anal. calcd. for C 112 H 115 N 15 O 6 : C, 76.12; H, 6.56; N, 11.89. F ound: C, 75.81; H, 6.60; N, 11.73. 3 4.4 J Compound 3 1 9 A sample of 3 12 (2.56g, 7.22mmol) and thionyl chloride (10.5mL, 144mmol) were combined in 120mL of chloroform and heated to reflux for 2 hours. The solvent was removed under reduced pressure to affo rd the crude acid chloride. The residue was dissolved in 100 mL of chloroform and cooled to 0 o C. 2 3c ( 1.41g, 1.61mmol ) and 4 dimethylaminopyridine ( 3.92g, 32mmol ) were dissolved in a small amount of chloroform and injected into the reaction vessel drop wise. The reaction was then allowed to warm to room temperature and stirred overnight. The organic phase was washed with 75 mL of 10% HCl three times followed by washing with 75 mL of 1M NaOH three times. The organics were dried with sodium sulfate and allowed to sit on the bench top for 1 hour resulting in precipitation of Na + 3 12 The precipitate was removed by filtration along with the drying agent. The organics were then removed under reduced pressure. The residue was recrystallized from ethanol (35mL) to afford 3 1 9 as yellow crystals ( 2.31g, 76% ). 1 H NMR (CHLOROFORM d ) ppm 0.46 (t, J =7.3 Hz, 9 H), 0.54 (t, J =7.3 Hz, 9 H), 1.12 (br. s., 18 H), 1.25 (br. s., 18 H), 1.47 (q, J =7.0 Hz, 6 H), 1.62 (q, J =7.0 Hz, 6 H), 3.79 (br. s., 6 H), 3.93 4.27 (m, 6 H), 6.56 (s, 1 H), 7.02 (d, J =10.0 Hz, 6 H), 7.21 7.42 (m, 18 H), 7.47 (d, J =7.0 Hz, 6 H), 7.56 (d, J =7.0 Hz, 6 H), 7.84 (t, J =7.8 Hz, 3 H), 8.28 (d, J =7.6 Hz, 3 H), 8.53 (d, J =7.3 Hz, 3 H), 9.20 (br. t, J =4.8, 4.8 Hz, 3 H) 13 C { 1 H} NMR 9.1, 9.5, 28.5, 29.3, 34.8, 36.9, 37.5, 39.1, 40.1, 70.4, 124.0, 124.6, 125.9, 127.4, 128.4, 129.5, 129.6, 129.9, 130.7, 135.1, 135.3, 137.9, 139.8, 142.4, 151.1, 151.3, 153.2, 155.9, 156.1, 160.1, 164.4 HRMS APCI : calcd for [M+H] + : m/z

PAGE 80

80 1851.0167 Found: m /z 1851.0208; calcd for [M+Na] + : m/z 1872.9986 Found: m/z 1872.9987 Anal. calcd. for C 118 H 127 N 15 O 6 : C, 76.55; H, 6.91; N, 11.35. Found: C, 7 6.61 ; H, 7. 05 ; N, 11. 35 3 4.5 General Procedure for Metal Complex Synthesis A quantity of the ligand (approx imately 0.2g) was dissolved in a small amount of ethyl acetate until completely dissolved. Two equivalents of the metal nitrate or tri flate salt were dissolved in 5 10mL of ethyl acetate and pipette d into the reaction vessel, commonly inducing immediate p recipitation The reaction was stirred for 1 2 hours to ensure complete reaction. The solid was collected by filtration on a fritted filter. 3 4.5 A Yb(3 7 a ) 3 (NO 3 ) 3 ((H 3 CH 2 C) 2 O) X ray quality c rystals were grown by diffusion of diethyl ether into methanol. 1 H NMR (METHANOL d 4 ) ppm 1.42 (br. d, J =7.3 Hz, 2 H), 1.84 (br. t, J =6.4, 6.4 Hz, 1 H), 8.20 8.44 (m, 6 H), 9.80 9.98 (m, 4 H), 18.07 (br. s., 2 H). Anal. calcd. for C 69 H 45 YbN 24 O 9 : C, 54.26; H, 2.97; N, 22.01. Found: C, 56.54; H, 4.46; N, 18.05 3 4.5 B Yb(3 7 b ) 3 (SO 3 CF 3 ) 3 (CH 3 OH) 3 X ray quality crystals were grown by diffusion of diethyl ether into methanol 1 H NMR (METHANOL d 4 ) ppm 0.69 0.85 (m, 2 H), 1.08 1.21 (m, 1 H), 8.09 8.27 (m, 6 H), 9.40 (d, J =3.7 Hz, 4 H), 9.72 9.88 (m, 2 H), 10.22 (br. s., 4 H), 13.11 13.33 (m, 4 H) Analyzed as Yb(3 7 b ) 3 (SO 3 CF 3 ) 3 Anal. calcd. for C 108 H 69 F 9 N 21 O 9 S 3 : C, 57.78 ; H, 3.10 ; N, 13.10 Found: C, 57.50 ; H, 3 .03 ; N, 12.81 3 4.5 C La 2 (3 17) (NO 3 ) 6 (CH 3 OH) 6 ((H 3 CH 2 C) 2 O) 3 X ray quality crystals were grown by diffusion of diethyl ether into methanol. 1 H NMR (Acetone) ppm 1.19 (s, 27 H), 2.25 (s, 9 H), 2.56 2.73 (m, 3 H), 2.89 2.98 (m,

PAGE 81

81 3 H), 3.97 (br. t, J =9.7, 9.7 Hz, 3 H), 4.52 4.75 (m, 3 H), 6.94 (d, J =7.2 Hz, 3 H), 7.09 (s, 3 H), 7.15 7.19 (m, 1 H), 7.29 (s, 6 H), 7.35 7.48 (m, 9 H), 7.51 7.59 (m, 3 H), 7.61 7.69 (m, 6 H), 8.43 8.55 (m, 3 H), 8.67 (d, J =8.0 Hz, 3 H), 9.18 (d, J =7.6 Hz, 3 H), 9.75 (d, J =9.2 Hz, 3 H). Anal. calcd. f or C 103 H 97 La 2 N 21 O 24 : C, 54.00; H, 4.27; N, 12.84. Found: C, 49.81; H, 4.08; N, 11.78. 3 4.5 D Er 2 (3 17) (NO 3 ) 6 (CH 3 OH) 6 ((H 3 CH 2 C) 2 O) 2 X ray quality crystals were grown by diffusion of diethyl ether into methanol 1 H NMR (METHANOL d 4 ) ppm 2.37 (s, 27 H), 3.82 4.08 (m, 9 H), 6.89 7.27 (m, 4 H), 7.68 7.83 (m, 4 H), 7.91 (br. s., 10 H), 8.57 (br. s., 9 H), 8.8 9 9.14 (m, 4 H), 9.14 9.41 (m, 6 H), 9.90 10.12 (m, 4 H), 10.47 10.90 (m, 6 H). Anal. calcd. for C 103 H 97 Er 2 N 21 O 24 : C, 52.70; H, 4.16; N, 12.53. Found: C, 51.31 ; H, 4.08 ; N, 11.92 3 4.5 E Yb 2 (3 17) (NO 3 ) 6 (CH 3 OH) 6 ((H 3 CH 2 C) 2 O) X ray quality crystals were grown by diffusion of diethyl ether into methanol. 1 H NMR (METHANOL d 4 ) ppm 2.17 (s, 27 H), 3.64 (s, 9 H), 4.89 5.06 (m, 6 H), 5.10 5.23 (m, 3 H), 5.25 5.41 (m, 3 H), 6.49 6.66 (m, 3 H), 6.88 7.03 (m, 3 H), 7.66 7.86 (m, 10 H), 8.31 (d J =2.0 Hz, 3 H), 8.41 (br. d, J =7.0 Hz, 6 H), 8.70 (t, J =7.6 Hz, 3 H), 8.88 (t, J =6.8 Hz, 6 H), 9.41 9.53 (m, 3 H), 9.76 9.93 (m, 6 H). Analyzed as Yb 2 (3 17)(NO 3 ) 6 (CH 3 OH) 3 Anal. calcd. for C 10 6 H 109 Yb 2 N 21 O 2 7 : C, 51.85 ; H, 4.47 ; N, 11.98 Found: C, 53.07; H, 4.64; N, 11.72. 3 4.5 F Yb(3 18) (NO 3 ) 3 (CH 3 OH) 3 X ray quality crystals were grown by diffusion of diethyl ether into methanol. 1 H NMR (METHANOL d 4 ) ppm 1.89 (s, 27 H), 1.99 2.15 (m, 27 H), 4.53 4.77 (m, 3 H), 5.47 5.81 (m, 6 H), 6.05 6 .39 (m, 6 H), 6.42 6.69 (m, 3 H), 7.49 7.80 (m, 9 H), 7.93

PAGE 82

82 8.43 (m, 18 H), 8.52 8.78 (m, 6 H), 8.96 9.19 (m, 3 H), 12.84 (br. s., 3 H), 13.72 (br. s., 1 H). Anal. calcd. for C 1 1 5 H 1 27 YbN 18 O 1 8 : C, 62.15 ; H, 5.76 ; N, 11.34 Found: C, 60.08; H, 5.2 6; N, 11.27. 3 4.5 G Yb(3 19) (SO 3 CF 3 ) 3 X ray quality crystals were grown by diffusion of acetone into pentane. 1 H NMR (METHANOL d 4 ) ppm 1.09 (br. t, J =7.2, 7.2 Hz, 3 H), 1.21 (br. t, J =7.3, 7.3 Hz, 9 H), 1.82 (s, 9 H), 1.89 (m, J =9.2 Hz, 18 H), 2.14 (d, J =3.4 Hz, 9 H), 2.16 2.31 (m, 6 H), 2.53 2.78 (m, 6 H), 4.55 4.74 (m, 3 H), 5.39 5.55 (m, 3 H), 5.55 5.73 (m, 3 H), 6.04 6.23 (m, 3 H), 6.23 6.41 (m, 3 H), 6.47 6.67 (m, 3 H), 7.53 7.64 (m, 6 H), 7.68 (d, J =7.3 Hz, 3 H), 7.97 8.11 (m, 9 H), 8.19 (m, J =7.3 Hz, 3 H), 8.27 (t, J =7.0 Hz, 6 H), 8.62 (d, J =6.7 Hz, 6 H), 8.92 (s, 3 H), 12.50 12.90 (m, 3 H), 13.50 13.73 (m, 1 H) Anal. calcd. for C 121 H 127 F 9 N 15 O 15 S 3 Yb : C, 58.80; H, 5.18; N, 8.50. Found: C, 59.07; H, 5.27; N, 8.47. 3 4.5 H Yb(3 16) 3 (SO 3 CF 3 ) 3 CH 3 OH X ray quality crystals were grown by diffusion of methyl tButyl ether into a saturated solution of methanol. 1 H NMR (Acetone) ppm 23.98 23.66 (m), 21.75 21.48 (m), 19.06 18.69 (m), 16.47 16.12 (m), 14.42 14.18 (m), 14.01 1 3.73 (m), 12.51 (d, J =5.5 Hz), 10.91 10.59 (m), 10.28 9.90 (m), 8.93 (d, J =6.0 Hz), 8.79 8.58 (m), 8.54 8.33 (m), 8.25 7.97 (m), 5.73 (d, J =6.0 Hz), 5.07 (br. s.), 4.10 (br. s.), 2.94 (d, J =6.0 Hz), 1.86 (br. s.), 1.72 1.48 ( m), 0.11 (d, J =5.5 Hz), 0.19 (br. s.), 1.34 1.69 (m), 2.34 2.62 (m), 2.83 (br. s.), 3.09 (br. s.), 3.18 3.56 (m), 4.12 4.35 (m), 4.33 4.54 (m), 4.57 4.68 (m), 4.73 5.27 (m), 5.40 5.73 (m), 6.32 (br. s.), 6.52 6.71 (m), 6.80 (s), 7.15 (s) 7.22 7.49 (m), 7.58 7.92 (m), 7.86 8.09

PAGE 83

83 (m), 8.32 (br. s.), 8.56 (d, J =7.3 Hz), 9.34 (s), 9.45 9.66 (m), 9.63 9.93 (m), 10.40 10.66 (m), 10.99 (d, J =6.9 Hz), 11.19 11.47 (m), 11.62 11.85 (m), 12.13 (s), 12.71 (s), 16.51 16.96 (m), 17.84 18.16 (m), 19.15 19.44 (m), 19.44 19.74 (m), 22.20 22.56 (m), 25.06 25.41 (m), 25.46 25.82 (m). Anal. calcd. for C 90 H 93 F 9 N 15 O 12 S 3 Yb: C, 53.59; H, 4.65; N, 10.42. Found: C, 51.84; H, 4.46; N, 10.04. 3 4.5 I Eu 2 (3 18) (NO 3 ) 6 (CH 3 OH) 3 X ray quality crystals were grown by diffusion of isopropyl ether into a saturated solution of Eu(3 18) (NO 3 ) 3 in methanol. 1 H NMR (METHANOL d 4 ) ppm 1.44 (s), 1.57 (s), 3.42 3.56 (m), 3.77 3.94 (m), 4.10 4.29 (m), 5.83 5.92 (m), 6.12 6.23 (m), 6.87 6.98 (m), 6.98 7.15 (m), 7.16 7.26 (m), 7.38 7.68 (m), 7.90 7.97 (m), 8.95 (s). Anal. calcd. for C 11 5 H 1 27 Eu 2 N 21 O 2 7 : C, 54.39 ; H, 5.04 ; N, 11.58 Found: C, 54.37; H, 4.78; N, 11.48. 3 4.6 X Ray Structure Solution Structure solutio ns were obtained by Dr. Patrick Hillesheim and Dr. Khalil Abboud. X Ray intensity data was collected at 100 K on either a Bruker DUO or Bruker SMART diffractometer using MoK radiation ( = 0.71073 ) or CuK ( = 1.54178 ) and an APEXII CCD area detector. Raw data frames were read by program SAINT and integrated using 3D profiling algorithms. The resulting data was reduced to produce hkl reflections, intensities, and estim ated standard deviations. Structures were solved and refined in SHELXTL6.1 59, 60 using full matrix least squares refinement. Where necessary, the program SQUE EZE, a part of the PLATON package 61 of crystallographic software, was used to calculate the solvent disorder area and remove its contribution to the overall intensity data.

PAGE 84

84 Figure 3 1 Common organic terde ntate N donor ligands found in the literature. Numerals on BTP are highlighting the triazine ring positions. Figure 3 2 Description of the position susceptible to attack in extraction experiments with actinides. 72, 74 Figure 3 3 BTP derivatives incorporating annulated rings for increased robustness.

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85 Figure 3 4 Proposed synthetic scheme for synthesis of tris BTP extractant.

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86 Figure 3 5 Proposed ligand synthesis of target picolinamide extractant Figure 3 6 Synthesis of 6 (5,6 diphenyl 1,2,4 triazin 3 yl)picolinic acid and attempted synthesis of diethyl derivative. i) Hydrazine hydrate. ii) Benzil, EtOH, 4hrs, reflux. iii) SeO 2 dioxane, 12hrs, reflux. iv) AgNO 3 Na OH, H 2 O/MeOH, 12hrs, r.t. v) 3,4 hexanedione, EtOH, 4hrs, reflux. Proposed Target Structure

PAGE 87

87 Figure 3 7 Synthesized extractants containing the 1,2,4 triazinyl picolinamide moiety. i) SOCl 2 CHCl 3 4hrs, reflux. ii) amine, DMAP, CHCl 3 2 days, r.t.

PAGE 88

88 Figure 3 8 1 H NMR comp arison of ligand 3 19 before (bottom) and after a 24 hour contact with 1M HNO 3 with the ligand in CD 2 Cl 2 (top).

PAGE 89

89 Figure 3 9 Representative solid state structure found for metal nitrates complexed with 1,2,4 triazine picolinamide ligands shown here by L a 2 (3 17)( NO 3 ) 6 La(NO 3 ) 6 3 counter anion shown as it is common to many complexes. Hydrogens, solvent, and disorder in alkyl substituents have been removed for clarity. Atoms represented by 50% ellipsoids. Lanthanum = orange, carbon = grey, nitrogen = b lue, and oxygen = red.

PAGE 90

90 Figure 3 10 Depiction of binding cavity surrounding M to highlight the distortion from ideal trigonal tricapped prismatic geometry. Blue and red bonds drawn as a visual aid while yellow bonds exist within the structure. Figure 3 11 Representative plot of UV/VIS spectra for titration of 3 19 with a 50:1 excess of Yb at varying time intervals (right) and change over time plot at max = 305nm (left). [L] approximately 2 x 10 5 M. 0.2 0.9 1.6 250 280 310 340 A (nm) 1 1.2 1.4 1.6 0 20 40 60 80 A Time (min) Dihedral Angle

PAGE 91

91 Figure 3 12 Plot of ln(A A t ) versus t ime from which the k obs was extracted as the slope. Figure 3 13 Representative plot of spectrum from titration of 3 19 with Yb(NO 3 ) 3 in acetonitrile. [L] approximately 2 x 10 5 M with M solution additions of approximately 5 L. 2.3 1.9 1.5 1.1 0 2.5 5 7.5 10 ln(A A t ) Time (min) 0 0.4 0.8 1.2 1.6 250 290 330 370 A (nm)

PAGE 92

92 Figure 3 14 Extr action efficiency for 3 7 a (open squares), 3 16 (circles), 3 17 (diamonds), 3 18 (triangles), and 3 19 (squares) from 1M nitric acid into dichloromethane. [M 3+ ] = 1 x 10 4 M and [L] = 1 x 10 3 M with 12 hour contact time. Figure 3 15 Comparison of extr action results for 3 19 with COSAN added (diamonds) and without COSAN (squares) from 1M nitric acid into dichloromethane. [M 3+ ] = 1 x 10 4 M [L] = 1 x 10 3 M, and [COSAN] = 3 x 10 3 M with 12 hour contact time. 0.0 5.0 10.0 15.0 20.0 25.0 30.0 La Ce Pr Nd Eu Gd Tb Dy Er Tm Yb E% 0.0 10.0 20.0 30.0 La Ce Pr Nd Eu Gd Tb Dy Er Tm Yb E%

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93 Figure 3 16 1 H NMR ( d acetone) analysis o f solution structure of tedentate 3 16. Free 3 16 (bottom), and in ascending order the 1:6, 1:3, 1:2, 1:1 (top) ligand to metal ratios. Table 3 1 Comparison of La(3 17)(NO 3 ) 3 Er(3 17)(NO 3 ) 3 and Yb(3 17)(NO 3 ) 3 solid state structures. La Er Yb M N Triazine () 2.702(1) 2.530(2) 2.523(1) M N Pyridine () 2.691(1) 2.490(2) 2.471(2) M O () 2.454(1) 2.326(2) 2.300(1) Twist ( ) 22.065(4) 12.812(9) 11.579(6) Ion. Rad. a () 1.03 0.89 0.87 (a) Shannon; Acta Crystallogr. A 1976 32, 751 Ionic r adii for CN = 6

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94 Table 3 2 Solid structure comparison of Yb(3 17)(NO 3 ) 3 Yb(3 18)(NO 3 ) 3 and Yb(3 19)(SO 3 CF 3 ) 3 Yb(3 17) 3+ Yb(3 18) 3+ Yb(3 19) 3+ M N Triazine () 2.523(1) 2.521(1) 2.531(3) M N Pyridine () 2.471(2) 2.472(1) 2.476(3) M O () 2 .300(1) 2.279(1) 2.301(2) Twist () 11.579(6) 12.479(2) 12.973(115) Table 3 3 Comparison of terdentate ligands in Yb(L) 3 3+ complexes to Yb(3 17)(NO 3 ) 3 Yb(3 7 a ) 3 3+,a Yb(3 7 b ) 3 3+,b Yb(3 16) 3 3+,b Yb(3 17) 3+,a M N Triazine () 2.465(1) 2.477(1) 2.474 (2) 2.523(1) M N Pyridine () 2.447(2) 2.461(1) 2.471(1) 2.471(2) M O/M N Triazine () 2.465(1) 2.487(1) 2.271(1) 2.300(1) Twist () 10.756(5) 10.475(6) 9.942(1) 11.579(6) (a) NO 3 complexes, (b) SO 3 CF 3 complexes Table 3 4 Experimentally determined k obs a nd k for 3 19 with Yb(NO 3 ) 3 in acetonitrile. M to L k obs (s 1 ) k ( M 1 s 1 ) 15 to 1 1.28E 03 4.12 30 to 1 2.20E 03 3.60 50 to 1 3.15E 03 3.15 65 to 1 4.87E 03 3.71 Table 3 5 Binding constants for 3 19 in acetonitrile for the metallation reaction M 3+ + L ML 3+ K +/ La 4.266 0.009 Eu 7.914 0.110 Yb 7.614 0.069

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95 Table 3 6 X ray data for reported crystal structures of nonadentate (3 17, 3 18, 3 19) and terdentate (3 7 a 3 7 b 3 16) metal complexes La 2 (3 17)(NO 3 ) 6 Er 2 (3 17)(NO 3 ) 6 Yb 2 (3 1 7)(NO 3 ) 6 Yb(3 18)(NO 3 ) 3 Empirical Formula C 103 H 97 La 2 N 21 O 24 C 103 H 97 ErN 18 O 15 C 105 H 103 N 21 O 26 Yb 2 C 112 H 112 N 18 O 15 Yb Total Reflections 40185 54385 18761 5536 Uniq. Reflections/ Reflections I >2 (I) 22967/20200 30261/22824 9684/8278 5536/4482 Collection Range ( ) 1.12 to 25.00 0.79 to 22.50 1.01 to 18.76 1.48 to 27.50 M r 2290.84 1994.25 2421.16 2123.24 Crystal System Triclinic Triclinic Triclinic Cubic Space Group P P P P2 1 3 Z 2 4 2 4 a ( ) 18.2537(10) 21.310(2) 17.6026(14) 23.7722(9) b () 18.390 (1) 21.575(2) 17.8227(15) c () 20.7899(12) 25.924(2) 20.5821(17) () 74.209(1) 82.036(2) 81.5270(10) () 89.492(1) 86.570(1) 81.6540(10) () 87.577(1) 84.975(1) 88.4920(10) V c ( 3 ) 6709.5(6) 11744.8(19) 6318.9(9) 13434.1(9) D c (g cm 3 ) 1.134 1.128 1.273 1.05 F ( 000 ) 2336 4116 2456 4400 [Mo K ] (mm 1 ) 0 .693 0.776 1.542 0.753 R 1 [ I > 2 (I)data] 0.0395 0.0575 0.0557 0.0582 wR 2 [ I >2 (I)data] 0.1082 0.1535 0.1583 0.1662 GoF 1.101 1.089 1.095 1.079 Largest Peak, deepest trough (e 3 ) +1.800, 1.233 +1.959, 1.351 +2.185, 1.223 +1.436, 0.632 R 1 = (||F o | |F c ||) / |F o | wR 2 = [ [w(F o 2 F c 2 ) 2 ] / [w(F o 2 ) 2 ]] 1/2

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96 Table 3 6 (cont.) Yb(3 19)(SO 3 CF 3 ) 3 Yb(3 7 a ) 3 (NO 3 ) 3 Yb(3 7 b ) 3 (SO 3 CF 3 ) 3 Yb(3 16) 3 (SO 3 CF 3 ) 3 Empirical Formula C 121 H 127 F 9 N 15 O 15 S 3 Yb C 69 H 45 N 23 O 6 Yb C 111 H 81 F 9 N 21 O 13 S 3 Yb C 90 H 93 F 9 N 15 O 12 S 3 Yb Total R eflections 125559 27563 66571 37661 Uniq. Reflections/ Reflections I >2 (I) 31899/22963 3307/2406 23419/20763 12824/12386 Collection Range ( ) M r 2465.09 1465.32 2357.9 2017.01 Crystal System Triclinic Trigonal Triclinic Monoclinic Space Group P P Cc Z 2 2 2 4 a ( ) 14.8807(3) 14.4423(10) 13.6476(9) 24.8539(6) b () 20.2373(4) 16.3938(10) 13.9870(3) c () 24.8721(6) 23.723(2) 23.0054(14) 28.8206(6) () 95.009(2) 88.036(1) () 101.027(2) 89.204(1) 107.791 () 107.138(1) 82.558(1) V c ( 3 ) 6942.5(3) 4285.2(6) 5100.5(6) 9687.0(4) D c (g cm 3 ) 1.182 1.136 1.535 1.383 F ( 000 ) 2554 1476 2394 4132 [Mo K ] (mm 1 ) 0.790 1.147 1.071 3.088 R 1 [ I > 2 (I)data] 0 .0469 0.0273 0.0347 0.0284 wR 2 [ I >2 (I)data] 0.1025 0.0731 0.0847 0.0679 GoF 0.914 1.05 1.022 1.055 Largest Peak, deepest trough (e 3 ) +0.982, 1.133 +0.629, 0.496 +1.713, 1.219 +0.747, 0.695 R 1 = (||F o | |F c ||) / |F o | wR 2 = [ [w(F o 2 F c 2 ) 2 ] / [w(F o 2 ) 2 ]] 1/2

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97 CHAPTER 4 TRIAZZOLE BASED LIGA NDS AS PREORGANIZED MIMICS OF BIS (1,2,4 TRIAZIN 3 YL) P YRIDINES SYNTHESIS AND EXTRAC TION PROPERTIES 4 1 Introduction It is clear that there is a preference in ligands for Ln and An for heterocyclic based nitrogen donors. This is significant due to the preference not to include phosphorous in extracting ligands because of secondary waste generation upon processing ligands after extractions. Bis ( 1,2,4 triazin 3 yl) pyridines (BTP) are known selective extr actants but the library of ligands containing various other heterocycles is small. Extension of this library into triazole based ligands is logical because of the literature precedent of complexes of bis triazole pyridine based ligands with various transi tion and Ln metals for catalysis and luminescence among other uses. 87 90 The only report of use of a bis triazole pyridine based donor for Ln/An separations was by Kolarik in 1999. 14 In this work the derivative tested was the 2,6 bis(5 alkyl/aryl 1,2,4 triazol 3 yl)pyridine. This compound was shown to have separation factors s of 1.3 to 1.85 though with a organic phase modifier of 2 bromohexanoic acid. When the organic phase was not modified and the extracted complex was the nitrate salt little to no extraction was observed. The effectiveness of this ligand under certain con ditions and the limited coverage it has commanded made this an interesting avenue to pursue to generate a new ligand family. Also, synthetically the triazole allows various derivatives to be formed by modulating the position of the nitrogens in the triazo le ring to increase the array of ligands.

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98 4 2 Results and Discussion 4 2.1 Ligands synthesis The synthetic scheme (Figure 4 1) centered on coupling a 1,2.3 triazole moiety with pyridine and a 1,2,4 triazine moiety and t ethering this donor set onto a trip henoxymethane platform to organize all the donors into a nonadentate extractant. The synthesis began with an oxidation of 2 chloropyridine with hydrogen peroxide to generate 2 chloropyridine N oxide. The next step was an insertion of a cyano group into t he 6 position of the pyridine ring with concurrent reduction using trimethylsilylchloride, and s odium cyanide. C ondensation of the 2 chloro 6 cyanopyridine with hydrazine hydrate resulted in 6 chloropicolinohydrazonamide. 2 chloro 6 (5,6 diphenyl 1,2,4 t riazin 3 yl)pyridine reaction of the 2 chloro 6 cyanopyridine with benzil which was followed by a Sonogoshira coupling using Pd(0)tetrakis triphenyl phosphine and c opper(I) iodide to generate 2 trimethylsilylethynl 6 (5,6 dip henyl 1,2,4 triazin 3 yl)pyridine from the 2 chloro 6 (5,6 diphenyl 1,2,4 triazin 3 yl)pyridine and trimethyl silyl acetylene. Finally the trimethylsilyl groups were cleaved using cesium fluoride to produce 2 ethynl 6 (5,6 diphenyl 1,2,4 triazin 3 yl)pyrid ine 4 7. 4 7 was coupled to the tris azide derivative ( 2 4 ) of the triphenoxymethane platform employing modified click reaction conditions f or this task (Figure 4 2) The usual conditions for click reactions, biphasic organic aqueous systems with a copper (II) salt and a reductant in the aqueous phase and the azide and acetylide in the organic phase, were not feasible for this task because of solubility issues with 2 4 Instead, the reaction was set up in a N 2 filled dry box using copper(I) iodide as catal yst with no reductant. 91

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99 4 2.2 Solid State Structure In an effort to determine the coordination geometry of 4 9 c rystal s were grown of X ray diffraction quality by diffusion of methyl tb utyl ether into a saturated solution of 4 9 in methanol. The crystal structure verified the expected 1:1 metal to ligand ratio and the nonadentate ligation even in the presence of nitrate counter anions. Figure 4 3 shows a pictorial representation of the structure with the donor ri ngs represented on the right for clarity. Table 4 1 highlights the relevant average bond lengths ; each set of bond was averaged as the structure was not strictly C 3 symmetric. Also included in Table 4 1 is the data from the previously reported structure of Yb(3 19) 3+ as both ligands have the di tPentyl triphenoxymethane base and was ideal for comparison. As expected on changing from the carbonyl oxygen donor in Yb(3 19) 3+ to the relatively softer triazole donor the bond length increases from 2.301(2) t o 2.421(2) T his change also affords a shorter M N Triazine bond in Yb(4 9) 3+ which could lead to more effective interaction of this moiety with the metal orbitals. The twist angle decreases with the donor modulation from 12.973(115) in Yb(3 19) 3+ to 1 0.651(10) in Yb(4 9) 3+ A literature example using bis 1,2,3 triazole pyridine exemplified the ability of this ligand to coordinate europium in a tris fashion in the presence of chlorate counter anions 88 The report ed bond lengths in the structure were Eu N Py ridine = 2.5832(39) and Eu N Triazole = 2.5121(41) T he ionic radii for Yb is 1.125 and fo r Eu is 1.206 for coordination number 8 with a difference of 0.081 this difference is smaller than the differenc e between the Eu N Triazole bond lengths in this bis (1,2,3 triazol 4 yl)pyridine and the 4 9 structures which is 0.091 The difference is similar for the Eu N Pyridine bond disparities between the structures which is 0.092 T his small shortening of th e

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100 bond lengths was not probed but most likely has to do with the steric constraint imparted by the triphenoxymethane scaffo ld forcing the donors closer in towards the metal ions. 4 2.3 Binding Constant Studies The binding constant K is a necessary descript or when analyzing the quality of an extractant. The metallation reaction was defined as M 3+ + L ML 3+ with the binding constant equation K = [ML] 3+ /[L][M 3+ ]. Though the extraction process across a phase boundary is a complex process high strength coord ination is always a necessity. Binding constants were determined using UV/VIS spectroscopy in acetonitrile to ensure fast equilibration. Ligands were typically dissolved in 3mL of acetonitrile at a concentration of approximately 2 x 10 5 M. Spike volume s were varied depending on metal titrant solution concentration to achieve a 1 to 1 M:L ratio at approximately 10 additions. Depending on the binding strength more additions may have been necessary. The results of these experiments are summarized in Tabl e 4 2 Compound 4 9 showed a smaller difference between the heavier Yb and lighter La than 3 19 which has a difference of almost 4 log units. The difference between Yb and La for 4 9 was 1.8 log units. The carbonyl causes a larger difference in binding constant than the triazole moiety most likely due to the increased donation of the carbonyl oxygen relative to the triazole nitrogen The results of these experiments, while in conditions different from the extraction conditions, are a useful guide to ext ractant strength. 4 2.4 Extractions Extractions performed with 4 9 towards a select group of Ln were performed extracting from 1M nitric acid into dichloromethane with a 10 to 1 ligand to metal ratio

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101 The results are represented in Figure 4 5. The result s for 3 19 are included in the figure for comparison as both ligands have the same alkyl substitution on the triphenoxymethane scaffold and therefore solubility differences should be negligible The extraction efficiency for all tested m etals decreased co mpared to 3 19 This was expected because the main structural difference between the two extractants was the replacement of the carbonyl group in 3 17 for a 1,2,3 triazole moiety in 4 9. Only a slight preference was detected for the smaller Ln while for 3 19 this preference is more pronounced. The deviation for 4 9 is within the experimental error so it is reasonable to discern that there is no preference. W hile the binding constant data indicated weaker coordination to La there was still a significant difference of approximately 2 log units which was not apparent in the extraction data. The solid state structure of Yb(4 9) 3 3+ showed a shorter M N Triazine bond length than in Yb(3 19) 3 3+ by 0.07 The twist angle in Yb(4 9) 3 3+ was smaller than in Yb(3 19) 3 3+ The triazine moiety has a smaller affinity for Ln than carbonyl and carbonyl is the a major contributor to the stability of the Yb(3 19) 3 3+ complex. 4 3 Conclusions A novel nonadentate ligand was synthesized bearing a combination of 1,2,4 triazin e, pyridine, and 1,2,3 triazole moieties all in triplicate The l igand is a unique example of a nonadentate ligand containing exclusively heterocyclic nitrogen donors. The solid state structure exhibited 1 to 1 metal to ligand ratio excluding all solvent and anions from the inner coordination sphere. The ligand showed a limited propensity towards extraction of Ln from acidic aqueous phases though the solid state structure with Yb( N O 3 ) 3 3+ showed that the ligand can coordinate with a 1:1 ratio and in an

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102 or ientation near ideal trigonal tricapped prismatic in the presence of strongly competing nitrate anions Further experiments are necessary to determine the ability of 4 9 to segregate An from Ln.

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103 4 4 Experimental 4 4 .1 General Considerations 1 H and 13 C N MR spectra were recorded on a Gemini300, Varian300, or Mercury300 NMR instrument at 299.99 MHz for the proton channel and 75.47 MHz for the carbon channel. All UV/ VIS spectra were recorded on a Varian Cary 50 spectrophotometer. E ach sample analyzed by ma ss spectrometry was dissolved in appropriate solvent and underwent direct injection through an autosampler, followed by ESI or APCI analysis with methanol (with or without 0.2% acetic acid ) as mobile phase. For MALDI, the solution was usually added onto th e matrix spot of dithranol, cyano 4 hydroxycinnamic acid, dihydroxybenzoicacid or terthiophene. Solvent was used only when necessary for DART. The ions were detected with the Agilent 6210 TOF MS while the data was Elemental analyses were pe rformed at the in house facilities at the University of Florida. All solvents unless otherwise noted were used as received and either HPLC or ACS grade. Metal nitrate salts were purchased from Sigma Aldrich. They were dried under vacuum but otherwise us ed as received. Metal solutions were made using 18 Millipore deionized water and TraceMetal grade HNO 3 (Fisher Scientific). Arsenazo(III) dye was used as a UV/VIS sensitizer for all metal extraction experiments. 2 chloropyridine, 4 1, was purchased from Sigma Aldrich and used without further purification. 2 chloropyridine N oxide 92 4 2, and 2 chloro 6 cyanopyridine 93, 94 4 3, were prepared accordin g to previously reported literature procedures. 4 4.2 Binding Constant UV/VIS Measurements For all binding constant experiments a quartz cuvette was used along with deoxygenated acetonitrile to allow for analysis down to = 240nm. 3mL of the ligand

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104 solution at approximately 7 x 10 5 M were pipetted into the cuvette using an automatic pipettor. The background consisted of tetrabutylammonium nitrate at a concentration of 1 x 10 2 M to ensure that the ionic strength was cons tant throughout. The free ligand spectrum was collected followed by addition of a spike of metal solution with a concentration approximately 2 x 10 3 M. The spike volume was chosen to added a 1:10 molar ratio M:L for each spike. The solution was then st irred for 5 minutes and the spectrum collected. This was repeated until the system reached equilibrium. The data was processed using Reactlab EQUILIBRIA created by Jplus Consulting. This global analysis software fits the UV/VIS spectral trends and outpu ts the binding constant. 4 4.3 Synthetic Procedures 4 4.3 A Compound 4 4 A 8.68g sample of 4 3 ( 62.7 mmol) was di ssolved in 200mL of ethanol and 75mL of hydrazine was added. The mixture was heated to reflux (80 o C) for 2 hours at which point the reaction m ixture was cooled to room temperature which induced crystal lization The flask was then placed in the refrigerator overnight. The resulting w hite crystalline solid was isolated by filtration, washed with cold water, dried under vacuum and the resulting 4 4 (9.61 g ) was used without further purification 1 H NMR (CHLOROFORM d) ppm 4.63 (br. s., 2 H), 5.13 (br. s., 2 H), 7.30 (dt, J =7.9, 0.7 Hz, 1 H), 7.62 7.70 (m, 1 H), 7.94 (dt, J =7.8, 0.8 Hz, 1 H). 4 4.3 B Compound 4 5 Compound 4 4 (9.61g, 56.3mmol) wa s combined with benzil ( 11.82 g, 56.3mmol) in 200 mL of ethanol. T he mixture was heated to reflux for 3.5 hours during which time yellow solid began to precipitate. The solvent was removed under reduced pressure

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105 and the residue was recrystallized from refl uxing methanol yielding 4 5 as yellow needle shaped crystals which were collected by filtration (18.52 g, 95%) 1 H NMR (CHLOROFORM d) ppm 7.32 7.50 (m, 6 H), 7.54 (d, J=7.9 Hz, 1 H), 7.68 (dd, J=17.7, 7.5 Hz, 4 H), 7.91 (t, J=7.9 Hz, 3 H), 8.62 (d, J=7.6 Hz, 1 H). 13 C {1H} NMR, 122.5, 126.3, 128.6, 128.7, 129.6, 129.9, 130.0, 130.9, 135.1, 135.4, 139.5, 152.3, 153.4, 156.2, 156.6, 159.7. HRMS: calcd for [M+H] + : m/z 345 Found: m/z 345 Anal. Calcd for C 20 H 13 ClN 4 : C, 69.67; H, 3.80; N, 16.25. Found: C, 69.42 ; H, 3.64 ; N, 16.13. 4 4.3 C Compound 4 6 In a N 2 filled dry box 4 5 ( 1.0 g, 2.9 mmol) was combined in a 100mL S chlenk flask with a 5% catalyst loading of palladium(0) tetrakis(triphenylphosphine) ( 0.17g, 0.29mmol), copper(I) iodide ( 0.03 g, 0.29mmol) and 80mL of tetrahydrofuran. T rimethylsilylacet y lene ( 0.46mL 3.2mmol) was then added to the flask by syringe The flask was rem oved fr om the dry box and dry, deoxygenated triethylamine ( 8.1 mL, 58 mmol) was added by syringe. The reaction was stirred at room temperature overnight. The dark brown solution was filtered over celite and the solvent removed from the filtrate under redu ced pressure. Final purification was achieved using column chromatography with silica gel eluting with 1:3 ethyl acetate/hexane. The solvent was removed under reduced pressure and 4 6 was isolated as a pale yellow solid ( 0.82 g, 70 %). 1 H NMR (CHLOROFORM d) ppm 0.30 (s, 9 H), 7.31 7.52 (m, 6 H), 7.60 7.76 (m, 5 H), 7.89 (t, J=7.8 Hz, 1 H), 8.61 (dd, J=7.9, 1.2 Hz, 1 H). 13 C {1H} NMR 0.3, 95.8, 103.5, 123.4, 128.5, 128.6, 129.1, 129.5, 129.8, 130.0, 130.8, 135.3, 135.5, 137.1, 143.9, 153.3, 156. 2, 156.5, 160.3. Anal. Calcd for C 2 5 H 22 N 4 Si : C, 73.86 ; H, 5.45 ; N, 13.78 Found: C, 73.63; H, 5.51 ; N, 13.27

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106 4 4.3 D Comp o und 4 7 A 0.20g portion of 4 6 ( 0.49 mmol) was dissolved in 150 mL of 1:1 H 2 O/THF. CsF ( 0. 09 g, 0.59 mmol) was added and the reaction wa s stirred for 3 hours. The extent of the rea ction was monitored by TLC. The solvent was removed and the residue was taken up in 75mL of dichloromethane. The organic layer was washed with 50mL of brine with a small amount of 10% HCl aqueous solution adde d. The organic solvent was dried with sodium sulfate and then removed under reduced pressure. The resulting residue was purified by column chromatography using silica gel eluting with 1:1 ethyl acetate/hexane. The solvent was removed under reduced press ure and 4 7 was isolated as a pale yellow solid ( 0.16 g, 97 % ). 1 H NMR (CHLOROFORM d ) ppm 3.22 (s, 1 H), 7.29 7.51 (m, 6 H), 7.59 7.77 (m, 5 H), 7.90 (t, J =7.8 Hz, 1 H), 8.63 (dd, J =7.9, 0.9 Hz, 1 H). 13 C { 1 H} NMR 78.0, 82.6, 123.8, 128.5, 128.6, 129.1, 129.5, 129.8, 130.0, 130.8, 135.2, 135.4, 137.2, 143.0, 153.4, 156.2, 156.5, 160.2 Anal. Calcd for C 2 2 H 14 N 4 : C, 79.02 ; H, 4.22 ; N, 16.76 Found: C, 7 8.6 4 ; H, 4.52 ; N, 1 6.41 4 4.3 E Com p ound 4 9 4 7 ( 0.36 g, 1.3 mmol) was combined with 2 4 ( 0.21 g, 0.23 mmol) and a 10% catalyst loading of copper iodide ( 0.02 g, 0.13 mmol) in a 100mL Sch lenk flask inside a N 2 filled dry box. The reaction was stirred overnight at room temperature The solvent was removed under reduced pressure and the residue taken up on ethyl acetate The organ ic layer was then washed wi th 1M NaOH ( 2 x 40mL), followed by 10% HCl (2 x 40mL), then 40mL of 1M NaOH and finally 40mL of brine. The solvent was dried with sodium sulfate and then removed under reduced pressure. Purification was completed by silica gel column chromatography eluting with 1:2 ethyl acetate:hexane and afforded

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107 4 9 (0.34g, 65%) as a yellow solid after evaporation of the solvent 1 H NMR (CHLOROFORM d) p pm 0.44 0.60 (m, 18 H), 1.05 1.24 (m, 36 H), 1.37 1.54 (m, 12 H), 3.93 (m, J=35.0 Hz, 6 H), 4.61 (br. s., 3 H), 4.93 (br. s., 3 H), 6.50 (s, 1 H), 7.09 (d, J=6.7 Hz, 6 H), 7.18 7.45 (m, 18 H), 7.55 7.67 (m, 12 H), 7.75 (t, J=7.9 Hz, 3 H), 8.28 (d, J=7.9 Hz, 3 H), 8.39 (d, J=7.6 Hz, 3 H), 8.61 (s, 3 H). 13 C {1H} NMR 9.1, 9.5, 28.1, 28.8, 29.1, 34.6, 36.8, 37.6, 39.0, 50.7, 70.0, 122.0, 122.9, 125.0, 125.2, 127.8, 128.3, 128.4, 129.5, 129.9, 130.5, 135.3, 135.5, 137.3, 137.4, 140.5, 143.5, 1 47.7, 150.9, 152.1, 152.4, 155.7, 156.0, 160.6. Anal. Calcd. For C 121 H 127 N 21 O 3 : C, 75.56; H, 6.66; N, 15.29. Found: C 75.41; H, 6.78; N, 15.41 4 4.3 F Compound Yb 2 ( 4 9 ) (NO 3 ) 6 (CH 3 OH) 6 ((CH 3 ) 3 COCH 3 ) 2 X ray quality crystals were grown by diffusion of methy l tButyl ether into a saturated solution of Yb 2 (4 9)(NO 3 ) 6 in methanol. 1 H NMR (METHANOL d 4 ) ppm 1.49 (t, J =7.0 Hz, 9 H), 1.61 (t, J =7.3 Hz, 9 H), 2.16 (m, J =9.5 Hz, 1 H), 2.56 (q, J =6.9 Hz, 6 H), 3.13 (br. s, 9 H), 3.81 3.96 (m, 3 H), 4.16 4.32 (m, 3 H), 4.37 4.53 (m, 3 H), 5.84 6.03 (m, 3 H), 6.37 (d, J =10.7 Hz, 3 H), 6.57 6.78 (m, 3 H), 7.68 7.90 (m, 9 H), 8.40 8.62 (m, 9 H), 9.01 (s, 6 H), 9.16 9.32 (m, 6 H), 9.46 (d, J =1.8 Hz, 3 H), 9.75 9.91 (m, 3 H), 10.39 (d, J =6.7 Hz, 6 H), 15.74 15.84 (m, 1 H). Analyzed as Yb 2 (4 9)(NO 3 ) 6 (CH 3 OH) 2 Anal Calcd. For C 1 2 3 H 1 35 N 27 O 2 7 Yb 2 : C, 54.60 ; H, 5.03 ; N, 13.98 Found: C, 54.74 ; H, 4.93 ; N, 13.94 4 4.4 X Ray Structure Solution Structure solutions were obtained by Dr. Patrick Hillesheim and Dr. Khalil Abboud. X Ray intensity data was collected at 100 K on either a Bruker DUO or Bruk er SMART diffractometer using MoK radiation ( = 0.71073 ) or CuK ( = 1.54178 ) and an

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108 APEXII CCD area detector. Raw data frames were read by program SAINT and integrated using 3D profiling algorithms. The resulting data was reduced to produce hkl re flections, intensities, and estimated standard deviations. Structures were solved and refined in SHELXTL6.1 59, 60 using full matrix least squares refinement. Where necessary, the program SQUEEZE, a part of the PLATON 61 package 61 of crystallographic software, was used to calculate the solvent disorder area and remove its co ntribution to the overall intensity data. Figure 4 1 Synthetic scheme for ligand arm 4 7. i) H 2 O 2 Acet. Acid, 80 C, 12hrs ii) NaCN, TMSCl. DMF, 80 C, 2 days iii) Hydrazine Hydrate, EtOH, 80 C 4hrs iv) Benzil, EtOH, reflux, 4hrs. v) Pd(0)( PP h 3 ) 4 Me 3 SiCCH CuI NEt 3 THF, 12hrs. vi) CsF, H 2 O/THF.

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10 9 Figure 4 2 Synthesis of the triazole based triphenoxymethane ligand 4 9 i) CuI, THF, 12hrs, r.t. Figure 4 3 Solid state structure of Yb(4 9) 3+ (left) and binding pocket (right). Hydro gens, solvent, alkyl group disorder, and anions removed for clarity. Atoms represented by 50% probability ellipsoids. Grey = carbon, blue = nitrogen, purple = ytterbium.

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110 Figure 4 4 Representative spectrum from titration of 4 9 with Yb(NO 3 ) 3 in ace tonitrile. The [L] was approximately 2 x 10 5 M. Figure 4 5 Extraction results from 1M nitric acid into dichloromethane for 3 19 (squares) and 4 9 (diamonds). [M] = 1 x 10 4 M and [L] = 1 x 10 3 M with a 12 hour contact time. 0 0.1 0.2 0.3 0.4 0.5 0.6 250 270 290 310 330 350 370 390 A (nm) 0.0 10.0 20.0 30.0 La Ce Pr Nd Eu Gd Tb Dy Er Tm Yb E%

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111 Table 4 1 Bond lengths and prism twist angle in Yb(4 9) 3+ with Yb(3 19) 3+ included for comparison. Yb(3 19) 3+ Yb(4 9) 3+ M N Triazine () 2.531(3) 2.465(3) M N Pyridine () 2.476(3) 2.491(2) M O/M N T riazole () 2.301(2) 2.421(2) Twist () 12.973(115) 10.651(10) Table 4 2 Measured binding constants for 4 9 in acetonitrile. The [L] was approximately 2 x 10 5 M. log( K ) +/ La 5.224 0. 008 Eu 7.281 0.0 84 Yb 7.037 0.0 16

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112 Table 4 3 X ray crystal data for the solid state structure of Yb 2 (4 9) (NO 3 ) 6 Yb 2 (4 9)(NO 3 ) 6 E mpirical Formula C 121 H 127 N 27 O 21 Yb 2 Total Reflections 94402 Uniq. Reflections/ Reflections I >2 (I) 31754/24801 Collection Range ( ) 1.66 to 27.50 M r 2641.58 Crystal System Triclinic Space Group P Z 2 a ( ) 13.8162(15) b () 13.9131(16) c () 40 .956(5) () 96.233(3) () 91.615(3) () 117.197(2) V c ( 3 ) 6933.9(14) D c (g cm 3 ) 1.265 F ( 000 ) 2700 [Mo K ] (mm 1 ) 1.41 R 1 [ I > 2 (I)data] 0.0576 wR 2 [ I >2 (I)data] 0.1174 GoF 1.096 Largest Peak, deepest trough (e 3 ) +2.631, 6.333 R 1 = ( ||F o | |F c ||) / |F o | wR 2 = [ [w(F o 2 F c 2 ) 2 ] / [w(F o 2 ) 2 ]] 1/2

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113 CHAPTER 5 THEORETICAL COMPARISON OF BIS ( 1,2,4 TRIAZIN 3 YL)PYRIDINES WITH ANALOGUES OF EXTRACTANTS FOR THE SEGREGATION OF LANTHANIDES AND ACTINIDES 5 1 Introduction To understand fully t he preferential bonding of bis (1,2,4 triazin 3 yl) pyridines ( BTP ) compared to other similar terdentate nitrogen donor ligands the investigation must be extended beyond structural analysis as this approach is limited in what it elucidates about the compl ex bonding picture. T heoretical calculations allow examination of the geometric and electronic structure which is necessary to unearth the finer details that make BTP selective. This approach is especially important in cases where similar bond lengths ar e found between Ln( BTP ) 3 3+ complexes and An( BTP ) 3 3+ complexes but in extraction experiments there is selectivity for An. BTP and dithiophosphinic acid ( DTPA ) both show excellent selectivity for Cm(III) over Eu(III) in biphasic extraction systems but ac cording to EXAFS data on the solution structure there is negligible differences between the solution state complexes 17, 25 A major shortcoming to this type of analysis is the lack of e xperimental data to bolster the quality of calculation results and to calibrate theoretical calculations The consequence of this is the quality of calculation results and their application to real systems remains ambiguous. 95, 96 This is especially true for Cm as its relative scarcity and radiolytic hazard make it a burden for experimental work The complexity of the calculation presents another difficulty and the main at tribute s this affects is the calculation time and hardware needs. The majority of calculations with f block elements require simplification of the ligand architecture in order to decrease the resources needed for computations Simplification of ligand

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114 sy stems is not always trivial as Eisenstein and co workers have shown with parallel calculations across the entire Ln series indicating how seemingly innocuous modification of alkyl substitution substantially affects the overall result of the calculation. 97, 98 Interpretation of the electronic structure for the metal ligand bond is a challenging task in that it is often a search for very small covalent contributions among the prevalent ionic interactions It is well established that both Ln and An complexes consist of predominantly ionic interactions but comparatively small magnitude differences exist in the covalent nature of their bonding. The goal of theoretical methods applied to Ln and An systems is to elucidate these small disc repancies because they are the source of different bonding behavio r arising from the more radially diffuse 5f orbitals of the An Ideally a theoretical method could be developed to screen lig ands. To create a r eliable theoretical approach ligands must be analyz ed in a theoretical regime with concurrent comparison to solid state and solution state structural data In the work reported here systems were evaluated from three different approaches First target structures were optimized at the DFT level. Second the electronic structure of the simplified target ligand arms were analyzed for characteristic electronic properties and the result s compared to those of a BTP derivative Third the orbital population of the ML 3 complexes were analyzed and compared to determine the extent of covalent bonding interactions Similar calculations were performed on BTP complexes for comparison to literature examples and novel solid stat e structures collected w ith synthesiz ed BTP d erivatives

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115 5 2 Results and Discussion 5 2.1 Geometry Optimizations T erdentate heterocyclic ligands frequently show monomeric structures unless combined with large excesses of ligand and t his is especially true when combined with the smaller Ln (S m Lu). 65, 99 101 Terpyridine only attains the ML 3 struc ture when in the presence of excess ligand and very weakly coordinating anions. 102 These literature results make BTP more striking in its coordination chemistry. Even addition of 1 to 1 combinations of 5 2 to An(III) in the presence of the strongly competitive nitrate ( NO 3 ) a nion forms preferentially the ML 3 3+ structure. 27 A comparison was performed between crystal structures of Ln with BTP in the literature, BTP structures grown for this dissertation, and the outputs of the geome try optimizations completed by Dr. I. F. Dempsey Hyatt of the Scott group The BTP ligands compared in this work are shown in Figure 5 1 and the results of the comparison in Table 5 1 Close agreement was seen between the solid state structure of Yb(5 2 ) 3 3+ reported by Drew et al. 27 with two BTP derivatives Yb( 3 7 a ) 3 3+ and Yb( 3 7 b ) 3 3+ The alkyl substitution is not the same in 5 2, 3 7 a and 3 7 b but after a th orough literature review only the solid state str ucture of Yb(5 2 ) 3 3+ was located for comparison For Yb(3 7 a ) 3 3+ the 6 position of the triazine ring contains a hydrogen atom and this lack of steric bulk most likely allows for the smaller bond lengths seen for this derivative. Ligand behavior with Ln wa s an essential part of these studies but t he ligand coordination with respect to Cm and Am was also a necessary focus A comparison was made between calculated bond lengths for the optimized geometry of Cm(5 1) 3 3+ and the same calculation reported in the literature by Maldivi and co workers 31 and Guillaumont 29 using different theoretical techniques The non alkylated BTP (5 1) was

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116 chosen for simplicity and to limit calculation time These results were compared against solution state structure data colle cted by Denecke et al. on Cm(5 2 ) 3 3+ (Table5 2) 25 The data indicated a small overestimation of the Cm N bonds in all cases and the deviation was larger than the experimental error It should be noted that the experimental data was collected with the n p ropyl derivative (5 2), possible accounting for the deviation The literature calculation bond lengths were 0.03 and 0.02 shor ter than the calculation result for the Cm N Pyridine and Cm N Triazine respectively. The calculation results for the Cm N Pyridine and Cm N Triazi ne were 0.07 and 0.06 longer than the EXAFS data respectively. The structure of Eu(5 1) 3 3+ was a lso optimized and this result was compared to the experimental results with Eu(5 2 ) 3 3+ which were in slightly better agreement. This data is also included in Table 5 2. The complete results of the geometry optimizations for all calculated compounds are s hown in Table 5 3. 5 2.2 Ligand Orbital Comparison The energy difference between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) has been used previously to dete rmine the absolute hardness of donating ligand s 103 The absolute hardness for ligands 5 1, 5 3, 5 4, and 5 5 was evaluated with this approach. The ligands were treated as a fragment made up of three ligands (3L) and the HOMO LUMO energy gap measured for t he combined fragment For 5 1 the donating nitrogen lone pairs are accumulated in the HOMO orbitals of the 3L fragment. The LUMO is comprised of the of the triazine aromatic system. It is

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117 thought that softer donors can increase the level of covalent character in the bonding with an appropriate metal that has orbitals of the proper energy and symmetry. The selectivity of 5 1 for An has been well documented but the driving force for selectivity is still unclear. 28, 64 A recent theoretical analysis was carried out by Petit and co workers 32 in a manner simil ar to that described above. A comparison was made between 5 1 the methyl substituted BTP (Me BTP) and terpyridine as L 3 fragments. The authors pointed out that though terpyridine has the lowest energy for its donating electrons i ts LUMO ( character) was at a much hig her energy. 5 1 and Me B TP had slightly higher energy donating orbitals but the LUMO of each was significantly closer in energy to the HOMO compared to terpyridine. 32 Pred ictably 5 1 has the smallest gap as it contains six softer donor 1,2,4 triazine rings within the fragment. Compound 5 4 contains an amide carbonyl oxygen donor yet it had only a 3 .0 kcal increase in the energy gap The triazole moiety thought to mimic th e bis tr iazine structure actually had a larger gap than 5 4 with a deviation from 5 1 of 3.5kcal. The largest gap was seen for 5 3 because coupling a carbonyl oxygen donor to a bipyridine represents the hardest donor group compared to other ligands a nalyz ed in this study The complete results of this analysis are collected in Table 5 4. 5 2.3 ML 3 3+ Electronic Structure The source of selectivity for BTP seems by the numerous literature examples to be rooted in the finer details of the electronic structur e of An coordination with bis 1,2,4 triazin 3 yl pyridines as compared with Ln( BTP ) 3 3+ compounds. T he extent of 5f orbital contribution to bonding in complexes is commonly analyzed for comparison to the 4f orbital contribution. It has been seen numerous times that the 5f are more radially

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118 extended and available to generate covalent interactions In many cases the extent of bonding of the s, p, and d orbitals in covalency is similar and therefore cannot be the differentiating factor. 21 Theoretical c alculations that can probe the orbital structure of Ln, Am, and Cm complexes are especially useful when standard, straightforward methods to discern enhanced covalent interaction like analysis of solid and solution sta te structure are inconclusive. Significant d eviation was not seen between the Ln and An complexes that were optimized ( Table 5 3) and the solid state structures from the ionic radii trend with the radius of Eu(III) being 0.95 Am(III) 0.98 and Cm(III) 0.97 38 All theoretical calculations were performed in the Gaussian program package. 104 Each calculation used the B3LYP functional, a relativistic small core effective core potent ial (RSC ECP) basis set for Eu, Am, and Cm, and the 6 31G* basis set for C, H, O, and N. The full geometry optimizations for each structure converged to within 2kcal/mol of the C 3 or D 3 symmetric complexes. Subsequent single point calculations were perfo rmed to compute the Mulliken population and the output was formatted for analysis with the AOMix program package. 105, 106 Orbital contribution percent ages were also reported along with the overlap integral and orbital population parameter to determine the character of the overlap 5 2.3A Molecular Orbital Visualizations Direct interpretation of molecular orbital results in the form of tex t output files is difficult because of the expansiv e amount of data Visual representations allow for a more complete description of the bonding as nuances in orbital directionality can be discovered. Difficulty also exists because large percentage contributions can be

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119 predicted due to similar energies o f metal and ligand orbitals but when visualized do not represent a measurable interaction because the spatial extent of the 4f and 5f orbitals is severely limited. This can lead to false positives as large contributions to a molecular orbital from a metal orbital can still result in negligible overlap. Kaltsoyannis and co workers 21, 107 provided an explanation for why some calculated results show increased interaction of f orbitals f or Am and Eu They state because these metals are actually more ionic as opposed to accepting more electron density through covalent bonds. The reasoning followed that Am and Eu can attain the +2 oxidation state more readily because the f 7 electron confi guration is a half filled subshell with its inherent greater stability compared to the f 6 configuration. This electron donation is read as covalent interaction but is really partial electron transfer. For all orbital visualization discussion HOFO and LUFO refer to the frontier orbitals either centered on the metal or L 3 fragment while HOMO and LUMO will be reserved to describe molecular orbitals of the ML 3 3+ complex. A representation of the HOMO [ 10] and HOMO[0] of Am(5 1) 3 3+ are shown in Figure 5 2 as e xample s of interactions that contain metal f orbital character Inspection of the molecular orbital data for HOMO[0] shows tw o interactions with the Am d or bitals (1.2% and 1.1% respectively) with two orbitals of the ligand (HOFO[0] at 23% and HOFO[ 1] at 9.1%) which could be interpreted as a weak bonding molecular orbital. This small bonding interaction is counterbalanced by a much larger 53.8% contribution from an Am f orbital (HOFO[ 5]) which has an anti bonding interaction with the same 23.1% HOFO[0] of the ligand thereby generating an essentially anti bonding contribution to the overall bonding picture. The population of this antibonding fra ction is also predicted to be higher in this

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120 portion of the orbital. From visual inspection of the molecular o rbitals in Figure 5 2 (right), it is clear that the character of the orbital is anti bonding Examination of the HOMO[ 10] orbital data indicates a positive population of 25.1% contribution of the Am HOFO[ 5] (f orbital) interacting with 23.6% of the lig and HOFO[0]. This orbital is depicted on the left side of Figure 5 2. Clearly it is the bonding combination associated with the antibonding character of the HOMO[0]. The m olecular orbital data for all complexes was evaluated in a similar manner 5 2.3B Bis 1,2,4 triazin 3 yl pyridine Molecular Orbital Descriptions Eu(5 1) 3 3+ Am(5 1) 3 3+ and Cm(5 1) 3 3+ were all treated with the same theoretical method to give a baseline for comparison to other literature studies with the same systems. The europium in Eu(5 1) 3 3+ show ed minimal covalent interaction with the ligand orbitals. Only one interaction of Eu f orbitals was seen in the HOMO[ 35] which consisted of 3.4% f orbital and 47.1% of the ligand HOFO[ 19] This molecular orbital is severely buried in ene rgy and should not be deemed indicative of a frontier orbital interaction. There is also one molecular orbital each for the metal d orbitals and s orbitals with contributions of 3.2% and 2.2% respectively. Overall this is insignificant relative to the e lectrostatic interactions that dominate the bonding picture. Am(5 1) 3 3+ on the other hand had noteworthy orbital interactions within an array or m olecular orbitals. Contributions from the f orbitals are seen in the HOMO[ 9], [ 11], and [ 17] with metal co ntributions of 39.2%, 36.3%, and 4.7% respectively. This is a substantial deviation from the behavior of Eu. The HOMO[ 9] is shown in Figure 5 3 Two overlaps can be seen at opposing lobes of the f orbital with the triazine rings of the ligand fragment

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121 The HOMO[ 10] and HOMO[ 13] also show bonding interactions but are more complex than the three orbitals just described. The case of the HOMO[ 10] will be covered here as both orbitals parallel one another in their behavior. The HOMO[ 10] is predicted t o have a mixture of character because it has a combination of positively populated orbital interactions from the Am HOFO[ 5] to the ligand HOFO[0] but also a negatively populated interaction indicating anti bonding between the same Am f orbital and the lig and HOFO[ 11] (Figure 5 4). The overall orbital character for the HOMO[ 10] of Am(5 1) 3 3+ is bonding and this can be elucidated from inspection of the percentage contributions, the overlap integral, and the absolute population values The Am HOFO[ 5] ha s a covalent, populated interaction with the ligand HOFO[0] with 25.1% and 23.6% contributions respectively. The same Am HOFO[ 5] has a negatively populated interaction with the ligand HOFO[ 11] (10.4%) in an anti bonding interaction. T he degree of bond ing interaction in the complex is larger than anti bonding but the bonding interaction also has a larger population Considering all the contributions the bonding mode should dominate the HOMO[ 10] orbital picture which is seen (Figure 5 4) There are multiple other d, s, and p contributions but all are less than 4% and deemed insignificant in the overall bonding picture. The Am(5 1) 3 3+ structure has 5 predicted f orbital bonding interactions with an average f orbital contribution of 30.0%. The valence orbital structure of Cm(5 1) 3 3+ has a substantially different energetic match with 5 1 than Am. The highest occupied orbitals in Am(5 1) 3 3+ are metal centered and contain the f electrons (f 6 electron configuration) but the analogous orbitals in Cm(5 1) 3 3+ ( f 7 ) are set within the molecular orbital manifold from HOMO[ 24]

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122 to HOMO[ 29]. This very clearly shows the energetic recession of the f orbitals moving from left to right across the actinide series. An analysis of the orbital structure of Cm(5 1) 3 3+ shows a diminished but existent f orbital contribution compared with Am(5 1) 3 3+ Three interactions between Cm f orbitals and ligand orbitals (HOMO[ 33], [ 43], [ 44]) with an average metal contribution of 17.0% were calculated The three molecular orbi tals are depicted in Figure 5 5 and it is interesting to note that HOMO[ 43] and HOMO[ 44] show interaction of the metal f orbital with the triazine rings while for Am (5 1) 3 3+ there are three molecular orbitals with interactions with the ligand triazine ri ngs. The results o f this analysis for 5 1 are in line with literature studies. 5 1 is predicted to interact with An with a degree of covalency that other terdentate N donor ligands and Ln(5 1) 3 3+ cannot. A ccording to the calculation results the f orbita l contribution is the determining factor in why 5 1 is able to selectively coordinate An over Ln Also, Eu(5 1) 3 3+ was the only complex that showed a lack of appreciable covalent contribution from its f orbitals. O nly the f orbitals show any real deviati on from complex to complex while the s, d, and p orbitals all exhibit similar, small percentage s ( < 4%) in a small number of molecular orbitals. 5 2.3C ( 1,2,4 Tria zin 3 yl ) Picolinamide A similar co mparison was made between Eu(5 4 ) 3 3+ Am(5 4 ) 3 3+ and Cm(5 4 ) 3 3+ which was an analogue of a triphenoxymethane derivative s 3 17, 3 18, 3 19 synthesized and reported in Chapter 3. The calculation results were compared against those of 5 1 as it is the literature precedent In each structure the total number of c ovalent interactions between the metal f orbitals with various ligand molecular orbitals

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123 decreased relative to M(5 1) 3 3+ which was expected as the total number of triazine rings decreased from 6 in the 5 1 structures to 3 in the 5 6 structures. The expec ted bonding picture was seen for Eu(5 6) 3 3+ congruent to Eu(5 1) 3 3+ and literature examples There were only three molecular orbitals that contained positive interaction one with the d obital, one with an s/p m ix, and another just with the s orbital T he maximum percentage contribution was 2.8% and the average donation was on the order of 2% which resided in the HOMO[ 16], HOMO[ 29], and HOMO[ 56] indicating insignificant covalent interaction The f orbital density resided in the filled HOMO[ 39] to HO MO[ 4 4] with with no indication of covalent overlap with the ligands The case of Am(5 6) 3 3+ was a bit more complex. The HOMO[0] to HOMO[ 4] orbitals were on average 75% metal f orbital with no overlap with ligand orbitals These molecular orbitals repre sent the non interacting f electrons electrons as Am(III) has an f 6 configuration. Three orbitals showed significant overla p with f orbital density with a contributio n of 8.4% in the HOMO[ 5], 8.6% in the HOMO[ 20], and 2.7% in the HOMO[ 26] for an averag e donation of 6.6%. As predicted there is a sharp decline relative to 5 1 but it was not expected that the drop off would be larger than 50% and that the total number of interactions would decrease For An affinity to be seen for 3 17, 3 18, a nd 3 19 th e preorganization of donors and constriction of movement will have to imbue selectivity to the ligands. The Cm(5 6 ) 3 3+ case was more divergent than the Am case. Similar to Cm(5 1) 3 3+ the orbitals containing the non i nteracting f electrons reside at lower energies and are within the molecular orbital manifold from HOMO[ 16] to HO MO[ 23] T here is one small s orbital contribtion in the HOMO[ 36] of 1.6% and a d otbiral contribution to the

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124 HOMO[ 15] of 2.0%. The f orbital contribution rsides in only 2 mole cualr orbitals, the HOMO[ 24] and the HOMO[ 30] (Figure 5 6) with large contribution of 43.7% and 43.1% respectively. Upon close inspection the donation in HOMO[ 24] is clearly coming from the oxygen of the amide carbonyl and in HOMO[ 30] the donation ar ises from the pyridine nitrogen lone pairs. Therefore even thoug h two strong covalent interactions are predicted with an average of 43.4% f orbital contribution upon visual inspection of the orbitals all interaction with ligand orbitals on the triazine rings were lost. The triazine rings are the source of selectivity in BTP so these ligands are not predicted to show the same selectivity for Cm as BTP type ligands. Validation of the se calculation results must be supported with experimental results in pl ace of open conjecture. 5 2 .3D (1,2,4 Triazin 3 yl)(1,2,3 T riazol 4 yl )Pyridine The same theoretical method was applied to Eu(5 5 ) 3 3+ and Cm(5 5 ) 3 3+ (Am(5 5 ) 3 3+ was not calculated due to problems associated with SCF convergence ) In Eu(5 5 ) 3 3+ there were only two perceived overlaps both including the 6s orbital. The first interaction was in the HOMO[ 35] and the second in the HOMO[ 50] with an average contribution of 4.5%, a very weak interaction. For Cm(5 5 ) 3 3+ there was a larger degree of overlap co mpared to Eu (5 5) 3 3+ Three interactions were seen between the Cm f orbitals and ligand orbitals. They arose in the HOMO[ 28], [ 29], and [ 30] with contribut ions of 21.5%, 22.7%, and 35.3% from the f orbitals, respectively. There were also four d orbit al interactions with an average contribution of 2.3% and one s contribution of 2.8%. Clearly the dominant effect originates in the f orbitals.

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125 The bonding interac tions for Cm(5 5) 3 3+ are shown in Figure 5 7. Upon visual inspection of the HOMO[ 28] HOMO[ 29], and HOMO[ 33] clearly depicted in all three molecular orbitals is interaction of metal f orbitals with combinations of the ligand pyridine lone pairs. T his was not an encouraging result A ddition of the triazole caused any covalent interaction with the triazine rings to be eliminated and no new interactions with the triazole ring s were apparent. This was surprising as bis triazole pyridines synthesized by Kolarik paralleled the behavior of BTP derivatives especially in higher pH conditions. In 0. 1M nitric acid solution separation factors as high as 140 were detected. The source of selectivity shown by the triazole moiety must be further investigated. 14 5 2.3E Pyridine Picolinamide Both Eu(5 3 ) 3 3+ and Cm(5 3 ) 3 3+ were given the same treatment as the previous ex amples while Am(5 3 ) 3 3+ was not calculated due to problems associated with SCF convergence 5 3 seems to promote d orbital interactions as a slight increase was seen in Eu(5 3 ) 3 3+ compared to previous calculated Eu complexes Three interactions were seen in the HOMO[ 22], [ 23], and [ 24] with contributions of 2.6%, 2.6%, and 5.1% and an average of 3.4%. This is still deemed weak in terms of the overall bonding picture. The Cm(5 3 ) 3 3+ structure showed covalent interactions in four molecular orbitals for the f orbitals and two for the d orbitals. The interactions of the f orbitals were rather large with contributions of 51.4%, 48.9%, 52.9%, and 36.9% to the HOMO[ 27], [ 28], [ 29], and [ 30] respective ly. All these interactions involved overlap with both the carbonyl oxygen of the amide linkage and the central pyridine ring. No overlap with the terminal ring was seen. Representative pictures of the HOMO[ 27] and HOMO[ 29] are

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126 shown in Figure 5 8. Th e d orbital interactions were centered in HOMO[ 23], and [ 24] with an average contribution of only 2.1%. It is difficult to say definitively that 5 3 will show selectivity for Cm over Eu at this time because of limited experimental comparison. The theo retical method predicted that Cm(5 3) 3 3+ has enhanced covalent interaction that Eu(5 3) 3 3+ does not exhibit and this arising from the Cm 5f orbitals. The only conclusion that can really unequivocally be state d is that potential exists in the ligand to mat ch the symmetry of the f orbitals if the energies/spatial extent also match. 5 3 Conclusions Theoretical c alculations have been performed with an array of ligands with Eu representative of the Ln block of elements and with Am and Cm Structures input for analysis contained the important donor fragments but were simplified to limit calculation time. The results allowed insight into the orbital structure of the ML 3 3+ complex and the orbital structure of the ligand fragments (L 3 ) A theoretical approach to discern the potential of target ligands for selective extraction has been developed that can discriminate between ligands that promote f orbital interactions from those that generate exclusively ionic interactions In all cases the d ifferentiating factor was the f orbital contribution to the bonding picture as contributions from the s, d, and p orbitals were small and only showed small deviations between the Ln and An complexes Comparison to literature examples showed parallels with the synthesized liga nds and showed some to be worthy of further experimental study with the chosen metals. Validation of the theoretical method is still necessary against actual structures especially in the case of Am and Cm as the total number of structures for physical

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127 analysis is detrimentally low Concurrent spectroscopic analyses are required to determine the quality of the molecular orbital electronic structure prediction

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128 5 4 Computational Details All density functional theory (DFT) calculations were carried o ut by Dr. I. F. Dempsey Hyatt with t he Gaussia 104 Spin unrestricted multiplicities were used to account for the formal f n configurations for the Ln and An. Each geometry optimization was carried out with use of the B3LYP functional and the 6 31 G basis set for C, H, O, and N. A small core relativi stic effective core potential (RSC ECP) was used for Eu, Am, and Cm. The RECP was taken from the EMSL basis set library which used work from the Stuttgart and Dres den groups. 108, 109 Single point energy calculations were performed to determine the Mulliken population analysis and th e output was processed by the AOMix program package. 105, 106 Spin contamination was closely monitored and found to remain near accepted levels. Orbital pictures were generated with Gabedit 110 Figure 5 1 Structures used as simplified analogues of synthesized structures for the basis for theoretical calculations and experimental data comparisons.

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129 Figure 5 2 Visual representation of the HO MO[ 10] (left) and the HOMO[0] (right) of Am(5 1) 3 3+ Figure 5 3 Am(5 1) 3 3+ depicting interaction between the ligand HOFO[ 3] and Am f orbital (HOFO[ 2]) with a covalent interaction within the HOMO[ 9].

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130 Figure 5 4 Am(5 1) 3 3+ HOMO[ 10] as viewed do wn the z axis highlighting the bonding interaction. Figure 5 5 Cm(5 1) 3 3+ HOMO[ 33], HOMO[ 43], and HOMO[ 44] visualization highlighting the bonding interactions.

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131 Figure 5 6 Cm(5 6) 3 3+ HOMO[ 24] (left) and HOMO[ 30] (right), note interaction with the carbonyl oxygens for HOMO[ 24] and N Pyridine in HOMO[ 30]. Figure 5 7 Bonding interactions between ligand molecular orbitals and Cm f orbitals. Left: HOMO[ 28], center: HOMO[ 29], right: HOMO[ 33].

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132 Figure 5 8 Depiction of the HOMO[ 27] and HOMO[ 29] for Cm(5 3) 3 3+ Table 5 1 Bond length comparison of experimental solid state structure data and literature values. Yb(5 2 ) 3 3+ Yb(3 7 a ) 3 3+ Yb( 3 7 b ) 3 3+ () () () Yb N Py 2.466(11) 2.447(2) 2.461(1) Yb N Trz 2.479(9) 2.465(1) 2.482 (1) Drew et al.; Inorg. Chem. Comm. 2001 4,12 Table 5 2 Comparison of theoretical calculation results to literature calculation and experimental results for M(5 1) 3 3+ complexes. Lit. Calc a Lit. Calc b, Lit. Calc c Calc Exp c Ionic Rad. d ( ) () () () () () Eu N Py ridine n.d. n.d. 2.64 2.61 2.56 0.01 0.95 Eu N Tr ianzine n.d. n.d. 2.63 2.60 2.56 0.01 Cm N Py ridine 2.61 2.63 2.65 2.64 2.57 0.01 0.97 Cm N Tr iazine 2.61 2.61 2.64 2.63 2.57 0.01 (a) Maldivi et al.; C. R. Chemie 20 07 10, 888 (b) Guillaumont; J. Mol. Str: THEOCHEM 2006, 771, 105 (c) Denecke et al.; Inorg. Chem 2005 44, 8418; Exptl. Data shown for Cm(5 4) 3 3+ (d) Shannon; Acta Crystallogr. A 1976 32, 751 Calculated structure ML(H 2 O) 6 3+

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133 Ta ble 5 3 Complete geometry optimization results for all M(5 1) 3 3+ M(5 3) 3 3+ M(5 4) 3 3+ and M(5 5) 3 3+ complexes. Eu(5 1) 3 3+ Am(5 1) 3 3+ Cm(5 1) 3 3+ Eu(5 3 ) 3 3+ Cm(5 3 ) 3 3+ N top ( ) 2.60 2.62 2.63 2.66 2.70 N py () 2.61 2.64 2.64 2.64 2.68 N bot () 2. 60 2.62 2.63 2.38 2.44 Twist ( ) 16.69 17.95 17.80 16.15 17.81 Table 5 3 (C ont.) Eu(5 4 ) 3 3+ Am(5 4 ) 3 3+ Cm(5 4 ) 3 3+ Eu(5 5 ) 3 3+ Cm(5 5 ) 3 3+ N top ( ) 2.65 2.69 2.67 2.63 2.64 N py () 2.62 2.66 2.67 2.64 2.67 N bot () 2.39 2.43 2.44 2.56 2.59 Twist ( ) 16.99 17.47 18.99 15.45 17.21 Table 5 4 HOMO LUMO gap for L 3 fragments (5 1) 3 (5 3) 3 (5 4) 3 and (5 5) 3 5 1 5 3 5 4 5 5 E LUMO E HOMO (kcal) 88.1 100.8 91.1 91.6

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134 APPENDIX 1 H NMR AND 13 C NMR SPECTRA Figure A 1 1 H NMR and 13 C NMR for Comp ound 2 4.

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135 Figure A 2. 1 H NMR and 13 C NMR for Compound 2 5.

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136 Figure A 3. 1 H NMR and 13 C NMR for Compound 2 6 a

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137 Figure A 4. 1 H NMR and 13 C NMR for Compound 2 6 b

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138 Figure A 5. 1 H NMR and 13 C NMR for Compound 2 6 c

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139 Figure A 6. 1 H NMR and 13 C NMR for Compound 3 7 a

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140 Figure A 7. 1 H NMR for Compound 3 7 b

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141 Figure A 8. 1 H NMR and 13 C NMR for Compound 3 9.

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142 Figure A 9. 1 H NMR and 13 C NMR for Compound 3 10.

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143 Figure A 10. 1 H NMR and 13 C NMR for Compound 3 11.

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144 Figur e A 11. 1 H NMR and 13 C NMR for Compound 3 12.

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145 Figure A 12. 1 H NMR for Compound 3 13.

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146 Figure A 13. 1 H NMR and 13 C NMR for Compound 3 15.

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147 Figure A 14. 1 H NMR and 13 C NMR for Compound 3 16.

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148 Figure A 15. 1 H NMR and 13 C NMR for Compound 3 17.

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149 Figure A 16. 1 H NMR and 13 C NMR for Compound 3 18.

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150 Figure A 17. 1 H NMR and 13 C NMR for Compound 3 19.

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151 Figure A 18. 1 H NMR for Compound La(3 17). Figure A 19. 1 H NMR for Compound Er(3 17).

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152 Figure A 20. 1 H NMR for Compound Yb(3 17). Figure A 21. 1 H NMR for Compound Yb(3 18).

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153 Figure A 22. 1 H NMR for Compound Yb(3 19). Figure A 23. 1 H NMR for Compound Yb(3 16) 3

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154 Figure A 24. 1 H NMR for Compound Yb(3 7 a ) 3 Figure A 25. 1 H NMR for Compound Yb(3 7 b ) 3

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155 Figure A 26. 1 H NMR fo r Compound Eu(3 18). Figure A 27. 1 H NMR for Compound 4 4.

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156 Figure A 28. 1 H NMR and 13 C NMR for Compound 4 5.

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157 Figure A 29. 1 H NMR and 13 C NMR for Compound 4 6.

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158 Figure A 30. 1 H NMR and 13 C NMR for Compound 4 7.

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159 Figure A 31. 1 H NMR and 13 C NMR for Compound 4 9.

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160 Figure A 32. 1 H NMR for Compound Yb(4 9).

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161 LIST OF REFERENCES (1) U.S. Energy Information Administration 2010 DOE/EIA 0484(2010) 13. (2) Congressional Research Service; Holt, M. 2009 RL33558 1 32. (3) Annua l Energy Outlook 2010; Moens, J. 2009 DOE/EIA 0383(2010) (4) Energy Information Administration 2002 RW 859 (5) Bennett, R. G. In In Alternatives to Direct SNF Disposal: Advanced Nuclear Fuel Cycles; 2003 NAE National Meeting Symposium in Honor of For eign Secretary Harold. K. Forsen; Idaho National Engineering and Environmental Laboratory: 2003; (6) Madic, C.; Lecomte, M.; Baron, P.; Boullis, B. C. R. Phys. 2002 3 797 811. (7) Nash, K. L.; Madic, C.; Mathur, J. N.; Lacquement, J. 2006 2622 2798. (8) Gryntakis, G.; Cullen, D. E.; Mundy, G. 1987 273 199. (9) Zhu, Y.; Chen, J.; Jiao, R. Solvent Extr. Ion Exch. 1996 14 61 68. (10) Zhu, Y.; Chen, J.; Choppin, G. R. Solvent Extr. Ion Exch. 1996 14 543 553. (11) Chen, J.; Zhu, Y.; Jiao, R. Sep Sci. Technol. 1996 31 2723 2731. (12) Hill, C.; Madic, C.; Baron, P.; Ozawa, M.; Tanaka, Y. J. Alloys Compd. 1998 271 273 159 162. (13) Guoxin, T.; Yongjun, Z.; Jingming, X.; Ping, Z.; Tiandou, H.; Yaning, X.; Jing, Z. Inorg Chem 2003 42 735 741. (14) Kolarik, Z.; Mllich, U.; Gassner, F. Solvent Extraction and Ion Exchange 1999 17 23. (15) Kolarik, Z.; Mullich, U.; Gassner, F. Solvent Extraction and Ion Exchange 1999 17 1155. (16) Ghiorso, A.; Harvey, B. G.; Choppin, G. R.; Thompson, S. G. ; Seaborg, G. T. Phys. Rev. 1955 98 1518 1519. (17) Jensen, M. P.; Bond, A. H. J. Am. Chem. Soc. 2002 124 9870 9877. (18) Seaborg, G. T. Radiochim. Acta 1993 61 115 122.

PAGE 162

162 (19) Pearson, R. G. J. Am. Chem. Soc. 1963 85 3533 3539. (20) Choppin, G. R. J. Alloys Compd. 2002 344 55 59. (21) Gaunt, A. J.; Reilly, S. D.; Enriquez, A. E.; Scott, B. L.; Ibers, J. A.; Sekar, P.; Ingram, K. I. M.; Kaltsoyannis, N.; Neu, M. P. Inorg. Chem. (Washington, DC, U. S. ) 2008 47 29 41. (22) Mazzanti, M.; Wietz ke, R.; Pecaut, J.; Latour, J.; Maldivi, P.; Remy, M. Inorg. Chem. 2002 41 2389 2399. (23) Karmazin, L.; Mazzanti, M.; Gateau, C.; Hill, C.; Pecaut, J. Chem. Commun. (Cambridge, U. K. ) 2002 2892 2893. (24) Karmazin, L.; Mazzanti, M.; Bezombes, J.; Ga teau, C.; Pecaut, J. Inorg. Chem. 2004 43 5147 5158. (25) Denecke, M. A.; Rossberg, A.; Panak, P. J.; Weigl, M.; Schimmelpfennig, B.; Geist, A. Inorg. Chem. 2005 44 8418 8425. (26) Petit, L.; Adamo, C.; Maldivi, P. Inorg. Chem. 2006 45 8517 8522. (27) Drew, M. G. B.; Guillaneux, D.; Hudson, M. J.; Iveson, P. B.; Russell, M. L.; Madic, C. Inorganic Chemistry Communications 2001 4 12 15. (28) Berthet, J.; Miquel, Y.; Iveson, P. B.; Nierlich, M.; Thuery, P.; Madic, C.; Ephritikhine, M. J. Chem. Soc Dalton Trans. 2002 3265 3272. (29) Guillaumont, D. Journal of Molecular Structure: THEOCHEM 2006 771 105 110. (30) Troxler, L.; Dedieu, A.; Hutschka, F.; Wipff, G. Journal of Molecular Structure: THEOCHEM 1998 431 151 163. (31) Maldivi, P.; Pet it, L.; Adamo, C.; Vetere, V. Comptes Rendus Chimie 2007 10 888 896. (32) Petit, L.; Daul, C.; Adamo, C.; Maldivi, P. New J. Chem. 2007 31 1738 1745. (33) Malone, J. F.; Marrs, D. J.; McKervey, M. A.; O'Hagan, P.; Thompson, N.; Walker, A.; Arnaud Neu F.; Mauprivez, O.; Schwing Weill, M.; et al J. Chem. Soc. Chem. Commun. 1995 2151 2153. (34) Dam, H. H.; Reinhoudt, D. N.; Verboom, W. Chem. Soc. Rev. 2007 36 367 377.

PAGE 163

163 (35) Arnaud Neu, F.; Boehmer, V.; Dozol, J.; Gruettner, C.; Jakobi, R. A.; Kraf t, D.; Mauprivez, O.; Rouquette, H.; Schwing Weill, M.; et al J. Chem. Soc. Perkin Trans. 2 1996 1175 1182. (36) Martin, K. A.; Horwitz, E. P.; Ferraro, J. R. Solvent Extr. Ion Exch. 1986 4 1149 1169. (37) Dinger, M. B.; Scott, M. J. European Journa l of Organic Chemistry 2000 2000 2467 2478. (38) Shannon, R. D. Acta Crystallogr. Sect. A 1976 A32 751 767. (39) Miguirditchian, M.; Guillaneux, D.; Guillaumont, D.; Moisy, P.; Madic, C.; Jensen, M. P.; Nash, K. L. Inorg. Chem. 2005 44 1404 1412. (40) Sassoon, R. E.; Aizenshtat, Z.; Rabani, J. J. Phys. Chem. 1985 89 1182 1190. (41) Wietzke, R.; Mazzanti, M.; Latour, J.; Pecaut, J. J. Chem. Soc. Dalton Trans. 1998 4087 4088. (42) Drew, M. G. B.; Foreman, M. R. S. J.; Hill, C.; Hudson, M. J. ; Madic, C. Inorg. Chem. Commun. 2005 8 239 241. (43) Foreman, M. R. S. J.; Hudson, M. J.; Geist, A.; Madic, C.; Weigl, M. Solvent Extr. Ion Exch. 2005 23 645 662. (44) Nilsson, M.; Ekberg, C.; Foreman, M.; Hudson, M.; Liljenzin, J.; Modolo, G.; Skar nemark, G. Solvent Extr. Ion Exch. 2006 24 823 843. (45) Nilsson, M.; Andersson, S.; Drouet, F.; Ekberg, C.; Foreman, M.; Hudson, M.; Liljenzin, J.; Magnusson, D.; Skarnemark, G. Solvent Extr. Ion Exch. 2006 24 299 318. (46) Geist, A.; Hill, C.; Modo lo, G.; Foreman, M. R. S. J.; Weigl, M.; Gompper, K.; Hudson, M. J.; Madic, C. Solvent Extr. Ion Exch. 2006 24 463 483. (47) Matloka, K.; Gelis, A.; Regalbuto, M.; Vandegrift, G.; Scott, M. J. Dalton Trans. 2005 3719 3721. (48) Horwitz, E. P.; Diamond H.; Kalina, D. G. ACS Symp. Ser. 1983 216 433 450. (49) Norrby, T.; Brje, A.; Zhang, L.; kermark, B. Acta. Chem. Scand. 1998 52 77 85. (50) Rudzevich, V.; Schollmeyer, D.; Braekers, D.; Desreux, J. F.; Diss, R.; Wipff, G.; Bohmer, V. J Org Chem 2 005 70 6027 6033.

PAGE 164

164 (51) Peters, M. W.; Werner, E. J.; Scott, M. J. Inorg. Chem. 2002 41 1707 1716. (52) Mitra, R.; Peters, M. W.; Scott, M. J. Dalton Trans. 2007 3924 3935. (53) Hubscher Bruder, V.; Haddaoui, J.; Bouhroum, S.; Arnaud Neu, F. Inorg. Chem. 2010 49 1363 1371. (54) Matloka, K.; Gelis, A.; Regalbuto, M.; Vandegrift, G.; Scott, M. J. Sep. Sci. Technol. 2006 41 2129. (55) Krejzler, J.; Narbutt, J.; Foreman, M. R. S. J.; Hudson, M. J.; Casensky, B.; Madic, C. Czech. J. Phys. 2006 56 d459 d467. Radiochim. Acta 2008 96 273 284. Seluck, P. Journal of Organometalli c Chemistry 2009 694 1678 1689. (58) Barboso, S.; Carrera, A. G.; Matthews, S. E.; Arnaud Neu, F.; Bohmer, V.; Dozol, J. F.; Rouquette, H.; Schwing Weill, M. J. Chem. Soc. Perkin Trans. 2 1999 719 724. (59) Bruker AXS, Madison, Wisconsin, USA. 2000 (60) Sheldrick, G. M. Acta Crystallogr A 2008 64 112 122. (61) Van der Sluis, P.; Spek, A. L. Acta Crystallogr. Sect. A: Found. Crystallogr. 1990 A46 194 201. (62) Drew, M. G. B.; Iveson, P. B.; Hudson, M. J.; Liljenzin, J. O.; Spjuth, L.; Cord ier, P.; Enarsson, A.; Hill, C.; Madic, C. J. Chem. Soc. Dalton Trans. 2000 821 830. (63) Drew Michael, G. B.; Hill, C.; Hudson, M. J.; Iveson, P. B.; Madic, C.; Youngs Tristan, G. A. Dalton Trans 2004 244 251. (64) Iveson, P. B.; Riviere, C.; Nierli ch, M.; Thuery, P.; Ephritikhine, M.; Guillaneux, D.; Madic, C. Chem. Commun. 2001 1512 1513. (65) Cotton, S. A.; Raithby, P. R. Inorg. Chem. Commun. 1999 2 86 88. (66) Drew, M. G. B.; Guillaneux, D.; Hudson, M. J.; Iveson, P. B.; Madic, C. Inorganic Chemistry Communications 2001 4 462 466. (67) Boucher, C.; Drew, M. G. B.; Giddings, P.; Harwood, L. M.; Hudson, M. J.; Iveson, P. B.; Madic, C. Inorganic Chemistry Communications 2002 5 596 599.

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165 (68) Riviere, C.; Nierlich, M.; Ephritikhine, M.; Madi c, C. Inorg. Chem. 2001 40 4428 4435. (69) Berthet, J.; Riviere, C.; Miquel, Y.; Nierlich, M.; Madic, C.; Ephritikhine, M. Eur. J. Inorg. Chem. 2002 1439 1446. (70) Suzuki, H.; mori, T. J. Chem. Soc. Perkin Trans. 1 1995 291 293. (71) Mincher, B. J.; Arbon, R. E.; Knighton, W. B.; Meikrantz, D. H. Applied Radiation and Isotopes 1994 45 879 887. (72) Nilsson, M.; Andersson, S.; Ekberg, C.; Foreman, M. R. S.; Hudson, M. J.; Skarnemark, G. Radiochim. Acta 2006 94 103 106. (73) Drew, M. G. B.; Fo reman, M. R. S. J.; Geist, A.; Hudson, M. J.; Marken, F.; Norman, V.; Weigl, M. Polyhedron 2006 25 888 900. (74) Hill, C.; Guillaneux, D.; Berthon, L.; Madic, C. J. Nucl. Sci. Technol. 2002 309 312. (75) Hudson, M. J.; Boucher, C. E.; Braekers, D.; De sreux, J. F.; Drew, M. G. B.; Foreman, M. R. S. J.; Harwood, L. M.; Hill, C.; Madic, C.; Marken, F.; Youngs, T. G. A. New J. Chem. 2006 30 1171 1183. (76) Fermvik, A.; Berthon, L.; Ekberg, C.; Englund, S.; Retegan, T.; Zorz, N. Dalton Trans. 2009 6421 6430. (77) Fermvik, A.; Ekberg, C.; Englund, S.; Foreman, M. R. S. J.; Modolo, G.; Retegan, T.; Skarnemark, G. Radiochim. Acta 2009 97 319 324. (78) Gorbyleva, O. I.; Evstratova, M. I.; Yakhontov, L. N. Khim. Geterotsikl. Soedin. 1983 1419. (79) Sago t, E.; Le Roux, A.; Soulivet, C.; Pasquinet, E.; Poullain, D.; Girard, E.; Palmas, P. Tetrahedron 2007 63 11189 11194. (80) Benson, S. C.; Gross, J. L.; Snyder, J. K. J. Org. Chem. 1990 55 3257 3269. (81) Konno, S.; Osawa, N.; Yamanaka, H.; Sanemitsu Y.; Kawamura, S.; Sakaki, M. J. Agric. Food Chem. 1995 43 838 842. (82) Ulucam, G.; Bey Phosphorus, Sulfur & Silicon & the Related Elements 2008 183 2237 2247. (83) Yu, W.; Wang, E.; Voll, R. J.; Miller, A. H.; Goodman, M. M. Bioorg. Med. Chem. 2008 16 6145 6155.

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166 (84) Hudson, M. J.; Foreman, M. R. S. J.; Hill, C.; Huet, N.; Madic, C. Solvent Extr. Ion Exch. 2003 21 637 652. (85) Colette, S.; Amekraz, B.; Madic, C.; Berthon, L.; Cote, G.; Moulin, C. Inorg. Chem. 2002 41 7031 7041. (86) Colette, S.; Amekraz, B.; Madic, C.; Bertho n, L.; Cote, G.; Moulin, C. Inorg. Chem. 2003 42 2215 2226. (87) Meudtner, R. M.; Ostermeier, M.; Goddard, R.; Limberg, C.; Hecht, S. Chem. -Eur. J. 2007 13 9834 9840. (88) Li, Y.; Huffman, J. C.; Flood, A. H. Chem. Commun. (Cambridge, U. K. ) 2007 2692 2694. (89) Fletcher, J. T.; Bumgarner, B. J.; Engels, N. D.; Skoglund, D. A. Organometallics 2008 27 5430 5433. (90) Brunet, E.; Juanes, O.; Jimenez, L.; Rodriguez Ubis, J. C. Tetrahedron Lett. 2009 50 5361 5363. (91) Meldal, M.; Torne, C. W Chem. Rev. 2008 108 2952 3015. (92) Alker, D.; Ollis, W. D.; Shahriari Zavareh, H. J. Chem. Soc. Perkin Trans. 1 1990 1623 1630. (93) Furukawa, N.; Ogawa, S.; Kawai, T.; Oae, S. J. Chem. Soc. Perkin Trans. 1 1984 1839 1845. (94) Altmann, E.; A ichholz, R.; Betschart, C.; Buhl, T.; Green, J.; Irie, O.; Teno, N.; Lattmann, R.; Tintelnot Blomley, M.; Missbach, M. J. Med. Chem. 2007 50 591 594. (95) Strittmatter, R. J.; Bursten, B. E. J. Am. Chem. Soc. 1991 113 552 559. (96) Guillaumont, D. J. Phys. Chem. A 2004 108 6893 6900. (97) Maron, L.; Eisenstein, O. New J. Chem. 2001 25 255 258. (98) Eisenstein, O.; Maron, L. J. Organomet. Chem. 2002 647 190 197. (99) Drew, M. G. B.; Hudson, M. J.; Iveson, P. B.; Russell, M. L.; Liljenzin, J.; Sklberg, M.; Spjuth, L.; Madic, C. J. Chem. Soc. Dalton Trans. 1998 2973 2980. (100) Semenova, L. I.; White, A. H. Aust. J. Chem. 1999 52 507 517.

PAGE 167

167 (101) Leverd, P. C.; Charbonnel, M.; Dognon, J.; Lance, M.; Nierlich, M. Acta Crystallogr. Sect. C: Cryst. Struct. Commun. 1999 C55 368 370. (102) Semenova, L. I.; Sobolev, A. N.; Skelton, B. W.; White, A. H. Aust. J. Chem. 1999 52 519 529. (103) Pearson, R. G. Proc. Natl. Acad. Sci. U. S. A. 1986 83 8440 8441. (104) Frisch, M. J., et al Gauss ian 09 Gaussian Inc., Wallingford, CT, 2009. (105) Gorelsky, S. I.; Lever, A. B. P. J. Organomet. Chem. 2001 635 187 196. (106) Gorelsky, S. I. 2007 6.36ed. (107) Ingram, K. I. M.; Tassell, M. J.; Gaunt, A. J.; Kaltsoyannis, N. Inorg. Chem. (Washingt on, DC, U. S. ) 2008 47 7824 7833. (108) Feller, D. Journal of Computational Chemistry 1996 17 1571 1586. (109) Schuchardt, K. L.; Didier, B. T.; Elsethagen, T.; Sun, L.; Gurumoorthi, V.; Chase, J.; Li, J.; Windus, T. L. J. Chem. Inf. Model. 2007 47 1045 1052. (110) Allouche, A. J. Comput. Chem. 2010

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168 BIOGRAPHICAL SKETCH Gary Guille t was born in Woonsocket, RI in 1981. He spent his formative years in Burrillville, RI until 1999 when he enrolled at the University of Florida in Gainesville, FL. He graduated Cum Laude with a degree in chemistry. He then entered the work force with a position at Southern Analytical Labs in Tampa, FL and also as a high school teacher at Sickles High School in Tampa, FL. In 2005 he enrolled in the graduate in organic chemistry program at the University of Florida under the guidance of Dr. Michael J. Scott. His work centered on ligands for the segregation of lanthanides and actinides from acidic aqueous phases. He completed the requirements for his D octor of P hilosophy in December 2010.