SYNTHESIS and CHARACTERIZATION of NEW UNSYMMETRICAL DIGLYCOLAMIDES for TRIVALENT LANTHANIDE METAL EXTRACTION by BENJAMIN GEORGE
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SYNTHESIS AND CHARACTERIZATION OF NEW UNSYMMETRICAL DIGLYCOLAMIDES FOR TRIVALENT LANTHANIDE METAL EXTRACTION By BENJAMIN GEORGE TOKHEIM A dissertation submitted in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY WASHINGTON STATE UNIVERSITY Department of Chemistry JULY 2016 © Copyright by BENJAMIN GEORGE TOKHEIM, 2016 All Rights Reserved © Copyright by BENJAMIN GEORGE TOKHEIM, 2016 All Rights Reserved To the Faculty of Washington State University: The members of the Committee appointed to examine the dissertation of BENJAMIN GEORGE TOKHEIM find it satisfactory and recommend that it be accepted. ____________________________________ Kenneth L. Nash, Ph.D., Chair ____________________________________ Robert C. Ronald, Ph.D. ____________________________________ Scot E. Wherland, Ph.D. ____________________________________ Mark P. Jensen, Ph.D. ii ACKNOWLEDGEMENTS I would like to thank my advisor, Ken Nash, for teaching me how to find patterns in the seemingly inexplicable and how to persevere through repeated failures. I would like to thank my mentor, Rob Ronald, for imparting a portion of his vast wisdom to me and for showing me how to delight in everyday experiences. I would like to thank my professor, Scot Wherland, for introducing me to the world of inorganic chemistry and for sharing his passion for teaching with me. I would like to thank my undergraduate assistant, Shane Kelly, for helping with the difficult task of synthesizing and purifying many new compounds. I would like to thank the Nash group post-doctoral associate, Joey Lapka, for sharing an office and sharing his knowledge. I would like to thank Yuji Sasaki of the Japan Atomic Energy Agency for his generous gift of TODGA. I would like to thank Gerhard Munske of the WSU Molecular Biology and Genomics Core for helping to elucidate structures with his HRMS expertise. I would like to thank Greg Helms and Bill Hiscox of the WSU Center for NMR Spectroscopy for many hours of assistance and sage advice. iii I would like to thank my fellow graduate students for their assistance and support, especially Guy Dutech, Ashleigh Kimberlin, Ian Hobbs, Jeff Berry, Bess O’Leary, Adam Burn, Jeff Johnston, Jessica Drader, and Colt Heathman. I would like to thank all my wonderful professors (Jim Togeas, Nancy Carpenter, Jennifer Goodnough, Rob Rossi, George Shuffelton, Steve Kennedy, and Rick Penning) and teachers (Vern Stevens, Deanna Jordahl, Maury Ferden, Butch Halterman, Teresa Goddard, Darwin Tebeest, and Dan Hampton) from whom I have learned so much and owe my passion for continued learning. I would like to thank my father, Gene Tokheim, who always says that I am a success, even after apparent failures. I would like to thank my brother, Sam Tokheim, who provides excellent advice and comic relief for every situation. I would like to thank my brother, Luke Tokheim, who always shares some of his positive outlook and creates fun wherever he goes. Lastly, I would like to thank my mother, Lucy O’Laughlin, who always listens and sees the beauty in everything. iv SYNTHESIS AND CHARACTERIZATION OF NEW UNSYMMETRICAL DIGLYCOLAMIDES FOR TRIVALENT LANTHANIDE METAL EXTRACTION Abstract by Benjamin George Tokheim, Ph.D. Washington State University July 2016 Chair: Kenneth L. Nash Twelve new unsymmetrical diglycolamide (UDGA) ligands have been synthesized as solvent extraction reagents for trivalent lanthanide ions from highly acidic nitrate media. The asymmetry in the extractant design arises from attaching nonpolar alkyl chains (hexyl, octyl, 2-ethylhexyl, 3,7-dimethyloctyl) to one amide group and smaller, more compact, cyclic alkyl groups (pyrrolidinyl, piperidinyl, morpholino) to the other amide moiety. This structural variant of a well-known cation receptor reduces the interfacial footprint of the extractant and is designed to increase the rate of phase transfer of the target cations. The partitioning of 152,154Eu(III) between aqueous phases of varying nitric acid concentrations (0.01-3 M) and a 0.05 M UDGA in 5% v/v 1-octanol/n-dodecane organic phase was measured radiometrically and compared to the symmetrical diglycolamide, N,N,N′,N′-tetraoctyldiglycolamide (TODGA). All twelve UDGA ligands quantitatively extracted trivalent Eu(III) cations from 1 M nitric acid. Separate solvent extraction slope analysis experiments were used to determine the stoichiometry and conditional v extraction equilibrium constant (K'ex) of the extracted Eu-UDGA complex in 5% v/v 1-octanol/n-dodecane. The metal-ligand complex stoichiometry in the extracted species was found to be approximately 1:3 for the UDGA ligands and TODGA while the conditional extraction equilibrium constants (K'ex) decreased with increasing ligand size and alkyl chain branching. Luminescence spectroscopy investigations established the relative stability and stoichiometry of the complexes in acetonitrile. The overall trends in the conditional extraction equilibrium constant (K'ex) and the 1:3 conditional stability constant (β103) followed a similar pattern, indicating a correlation between complex stability and ligand structural features. vi TABLE OF CONTENTS Page ACKNOWLEDGEMENTS ...................................................................................................... iii ABSTRACT ................................................................................................................................ v LIST OF TABLES ...................................................................................................................... x LIST OF FIGURES ................................................................................................................. xii CHAPTER ONE: INTRODUCTION 1. THE ATOMIC AGE ................................................................................................... 1 2. SOLVENT EXTRACTION COMPLEXANT DEVELOPMENT ........................... 13 3. REFERENCES ......................................................................................................... 33 CHAPTER TWO: SYNTHESIS AND CHARACTERIZATION OF NEW UNSYMMETRICAL DIGLYCOLAMIDES 1. INTRODUCTION .................................................................................................... 40 2. MATERIALS ............................................................................................................ 46 3. METHODS ............................................................................................................... 47 4. SYNTHETIC DESIGN OBJECTIVES .................................................................... 49 5. SYNTHESIS AND PURIFICATION OF LIGANDS 1-9........................................ 51 Flash Chromatography: CombiFlash® Rf+ Lumen™...................................... 58 6. SYNTHESIS AND PURIFICATION OF LIGANDS 10-12.................................... 63 Flash Chromatography: MPLC #3 .................................................................... 71 7. CONCLUSIONS....................................................................................................... 73 vii 8. REFERENCES ......................................................................................................... 75 CHAPTER THREE: TRIVALENT LANTHANIDE METAL EXTRACTION BEHAVIOR BY NEW UNSYMMETRICAL DIGLYCOLAMIDES 1. ABSTRACT .............................................................................................................. 77 2. INTRODUCTION .................................................................................................... 77 3. MATERIALS ............................................................................................................ 81 4. METHODS ............................................................................................................... 83 Radiotracer 152,154Eu Experiments ..................................................................... 84 ICP-MS Ln Experiments................................................................................... 86 5. EQUILIBRATION TIME ......................................................................................... 87 6. THIRD PHASE FORMATION ................................................................................ 90 7. LIGAND SOLUBILITY ........................................................................................... 92 8. NITRIC ACID EXTRACTION ................................................................................ 95 9. EU(III)-UDGA COORDINATION COMPLEXES ............................................... 100 10. NITRIC ACID DEPENDENCE EXTRACTIONS .............................................. 113 11. NITRATE DEPENDENCE EXTRACTION ........................................................ 124 12. LANTHANIDE SERIES EXTRACTIONS ......................................................... 125 13. CONCLUSIONS................................................................................................... 135 14. FURTHER WORK ............................................................................................... 136 15. REFERENCES ..................................................................................................... 137 CHAPTER FOUR: PROBING THE EUROPIUM-UNSYMMETRICAL DIGLYCOLAMIDE COMPLEX USING LUMINESCENCE SPECTROSCOPY 1. INTRODUCTION .................................................................................................. 141 2. MATERIALS .......................................................................................................... 146 viii 3. METHODS ............................................................................................................