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Since 2000, when the Nobel Prize in Chemistry as awarded for conductive polymer research few studies have been performed concerning the conductive capabilities of discrete organometallic compounds. For this project, organometallic compounds were formed specifically with a transition metal included in the structure. Through oxidation and reduction reactions, the variation in the electrical conductivity could allow for an analysis of whether this unique structure would allow for tunability. The goal of this research was to begin with aromatic substituted fulvenes and perform various multistep synthesis processes, utilizing thallium salt intermediates, to produce several disubstituted cyclopentadienyl rhenium complexes. In this project, different rhenium complexes were synthesized accurately and with high yield utilizing methods that were straightforward and generated replicable results. Through melting range analysis, IR spectroscopy, 13C NMR, and 1H -NMR, the identity and purity of these compounds were confirmed.
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.