| Summary: | The aqueous chemistry of bis(maltolato)oxovanadium(IV), VO(ma)₂, bis(kojato)oxovandium(IV, VO(ka)₂, and bis(maltolato)dioxovandate(V), [VO₂(ma)₂] were studied as part of a research interest regarding their potential as insulin mimetic therapeutic agents. UV-Visible spectroscopy provided information regarding changes in the immediate vanadium environment with variable pH, and determined that oxidation of VO(ma)₂ and VO(ka)₂ occurs upon exposure to air. Variable pH cyclic voltammetric electrochemical investigation of the compounds of interest revealed that only VO(ma)₂ displayed reversible electrochemical behaviour. Room temperature and frozen solution ESR spectral parameters for the complexes were determined. Reduction of [VO₂(ma)₂]⁻ to VO(ma)₂ in acidic solution was determined by ESR spectroscopy. ⁵¹V NMR spectroscopy was used to probe the type, and stoichiometry, of complexes present in aqueous solution as a function of pH. Oxidation of VO(ma)₂ and VO(ka)₂ to vanadium(V) complexes was proven by ⁵¹V NMR spectra. Potentiometric titrations were used to determine ligand protonation constants, and metal-ligand stability constants.
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