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This dissertation investigates the synthesis and characterization of several rhenium Schiff base complexes as potential radiopharmaceuticals for imaging and therapeutic purposes. A series of acetylacetone derived tetradentate N 2 O 2 Schiff base ligands (i.e., acac 2 en, acac 2 pn, acac 2 dmpn) were reacted with a rhenium (V) starting material (i.e., n-Bu 4 N[ReOCl 4], ReOCl 3 (PPh 3) 2) to yield a series of compounds. In most cases, reaction's involving [n-Bu 4 N][ReOCl 4] with two equivalents of ligand in ethanol yielded monomer complexes of the form trans -[ReO(Ligand)X]. The type of axial substituent, X = Cl -, H 2 O, ReO 4 -, MeO -, found trans to the rhenium oxo group can be adjusted by altering the reaction conditions. A similar reaction utilizing ReOCl 3 (PPh 3) 2, one equivalent of the ligand, and triethylamine yielded [mu]-oxo dimer complexes, trans -[Re 2 O 3 (Ligand) 2]. The conversion of rhenium (V) Schiff base monomer complexes into [mu]-oxo dimer complexes was investigated to gain a better understanding of conditions that yield monomer compounds. Experiments reacting trans -[ReO(acac 2 pn)Cl] with various solution conditions led to the proposal of a dimer formation mechanism that involves two pathways: (1) addition of base(OH - ) and (2) addition of water to generate a trans aquo species and additional water molecules to deprotonate the coordinated water molecule. The rhenium (V) monomer complexes, trans -[ReO(acac 2 en)OH 2]Cl and trans -[ReO(acac 2 pn)Cl], were also reacted with phosphine ligands to potentially generate a bis -phosphine(Schiff base)rhenium(III) cationic complexes, trans -[Re(Ligand)(PR 3) 2] + . The trans -[ReO(acac 2 en)H 2 O]Cl complex yielded the Re (III) complex when reacted with phosphines, while the Schiff base ligand of the [trans -ReO(acac 2 pn)]Cl complex underwent an intramolecular rearrangement to yield an asymmetric complex, [cis -ReO(acac 2 pn)PR 3]X. A mechanism is proposed for the rearrangement of the Schiff base ligand in the complex upon treatment with phosphine ligands. Further experiments with other soft monodentate ligands (i.e., thiocyanate, cyanide) yielded neutral asymmetric complexes. A series of experiments investigated the removal radioactive Tc-99 from solution through precipitation. The study focused on precipitating agents that could be added to a simulated waste stream at a uranium reprocessing plant to remove Tc-99 as a pertechnetate ion pair or a reduced Tc (IV) complex.
The dramatic dependence of Re-binding to functionalized hydrazines on the nature of the coligands associated with the metal site has led to an examination of alkoxy and thiolato ligand types. The observation that multidentate thiolate ligands are highly effective in this latter role suggests the design and synthesis of new chelating polythiolate ligands with high binding affinities for radiometallic nuclides and of functionalized polythiolate ligands for the preparation of radionuclide-conjugated antibodies or peptides and the preparation and characterization of their complexes not only with the Group 7 metals Tc and Re but with the Group 13 metals Ga and In, which also possess radionuclides with useful properties. Since the rational design of these novel bifunctional conjugates requires a fundamental understanding of the coordination chemistry of relevant metals with polythiolate ligands whose syntheses and properties remain unexplored, effort has been directed toward the preparation of novel polythiolate ligands and the characterization of their complexes with Group 7 and Group 13 metals. This report describes studies on several complementary aspects of the coordination chemistry of the pyridinethiolate derived ligands 2-HSC5NH3-SiR3, 2-HSC5NH3-6-SiR3 and 2-HSC5NH2-3,6-SiR3 and the potentially bifunctional polythiolate ligand HOOCCH2Si(CH2CH2SH)3 have been synthesized; of several aspects of rhenium-hydrazido and rhenium-thiolate chemistry have been developed; of Ga and In complexes of the 2-pyridinethiolate class of ligands have been synthesized and structurally characterized; and of the general coordination properties of the 2-pyrithinethiolate and related ligand types.