1. Synthesis and Characterization of a Vanadium Based Transition State Mimic for Organophosphate Hydrolase 2. Catalytic Oxidation of Thioanisole and 2-Chloroethyl Ethyl Sulfide Using Resin Bead Supported Oxoperoxidovanadium(V) Complexes
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Two vanadium(V) complexes were prepared for different projects. First the ONS tridentate ligand 14 was prepared according to literature procedure. This ligand was chosen to make the ONS dioxovanadium complex 15 for conjugation to a protein and to eventually elicit catalytic antibodies for the hydrolysis of the chemical weapon VX. Complex 15 was prepared in 65% overall yield and a full characterization was performed including X-ray diffraction. Initial screening performed at the Naval Research Laboratory indicated an IC50 of 84 nM for inhibition of a bacterial cholinesterase. It was also found to be 50% as effective as the control antiobiotic Ceftazidime at inhibiting certain strains of the potential biological weapon Burkholderia psedumallei. Attempts to deprotect 15 led to its degradation from the reaction conditions needed to deprotect the S-benzyl group. A tripodal amine vanadium(V) complex K[VO(O2)LYSNTA] 18 was synthesized in order to prepare gold nanoparticles (AuNPs) functionalized with a catalyst capable of degrading the chemical weapon sulfur mustard. Vanadium(V) peroxo complexes with tripodal amine ligands are the most effective vanadium catalysts for oxidation reactions, and also avoid the over oxidation of sulfides to sulfones. The ligand lysine-NTA 16 was chosen as it contains a tripodal amine chelation head and a pendant amine tail available for eventual attachment to solid supports. Complex K[VO(O2)LYSNTA] 18 was successfully synthesized and fully characterized. Comparisons were made to similar vanadium(V) peroxo complexes with other tripodal amine ligands. Vanadium capped 19.5 nm diameter gold nanoparticles 23 were prepared and ICP-AES results indicated there were 3,630 vanadium atoms per nanoparticle yielding a minimum loading efficiency of 20.8% assuming there is one vanadium complex per gold surface atom. The availability of the pendant amine also allowed for the synthesis of vanadium functionalized polymer beads 21. Catalytic tests were performed to test the prepared compounds for sulfide oxidation. The oxidation of thioanisole was first studied using UV-Vis spectroscopy. The vanadium capped AuNPs 23 could not be used for catalysis, as attempts to bring them into acetonitrile resulted in aggregation. Complex K[VO(O2)LYSNTA] 18 displayed a first order rate constant of k = 1.27 ± 0.27 x 10-3 s -1 , and the polymer supported catalyst 21 had a value of 1.01 ± 0.72 x 10-4 s -1 . The literature value for K[VO(O2)HEIDA] 19 is 2.00 ± 0.29 x 10-3 s -1 . The compounds were also tested for the degradation of the chemical weapon analog 2- chloroethyl ethylsulfide (2-CEES) using GC-MS. The complex K[VO(O2)LYSNTA] 18 degraded 2-CEES into the sulfoxide with a k value of 1.58 ± 0.31 x 10-3 s -1 and a half-life of 6.9 minutes. Kinetic data could not be obtained for the literature complex K[VO(O2)HEIDA] 19 as the reaction was complete by the time the first data point could be obtained. The literature complex K2[VO(O2)NTA] 20 had a k value of 8.08 ± 0.01 x 10-2 s -1 . The polymer anchored K[VO(O2)LYSNTA] 21 had a k value of 1.34 ± 0.14 10- 4 s -1 and a half-life of 97 minutes.