Abstract
d-H2Pen-binding behavior to [VO(acac)2] at pH=7.00, 7.50 and 10.0 has been studied in thermodynamic viewpoint using UV/VIS spectroscopy. The optical absorption spectra of [VO(acac)2] were analyzed in order to obtain binding constants and stoichiometries using SQUAD software. The estimation of binding constant at various temperatures enabled us to calculate all of the thermodynamic parameters of binding using the van't Hoff equation. Studies of described reactions at pH=7.00, 7.50 and 10.0 show exothermic, endothermic and exothermic modality, respectively. d-penicillamine is a potentially tridentate ligand, but the pKa for the ‒ COOH, NH3 and S‒ H groups are 1.99–2.00, 8.0 and 10.6, respectively, as a result S‒H can not release proton at pH=7.00 and pH=7.50, so the coordination of S is not possible except at strong alkali mediums. At pH=7.00, d-H2Pen converts [VO(acac)2] to a vanadyl Schiff base complex (coordination mode is N2O2). At pH=7.50, d-H2Pen is converted to HPen− and the exchange of acac− with HP...
Highlights
IntroductionNumerous studies in experimental animals have shown that tolerable levels of vanadium-containing compounds can normalize plasma glucose, lipids and the thyroid hormone and at least partially counteract the increased
The VO(IV)-binding capabilities to a type of amino acid (D-penicillamine) have been briefly surveyed and different coordination modes of the ligand have been suggested via the differences in thermodynamic entities at different pHs
In contrast with previous studies that VO(IV) ion has undergone different coordination modes facilities with different ligands or suggested structures of the coordination of a ligand with multiple kinds of potential donors to a vanadyl ion have been obtained with other spectral techniques [15]
Summary
Numerous studies in experimental animals have shown that tolerable levels of vanadium-containing compounds can normalize plasma glucose, lipids and the thyroid hormone and at least partially counteract the increased. The parameters that define this dependency were analyzed with the aim of obtaining further information with regard to the differences of reactants and products’ charges at different pHs, in another research it has been shown that the product at Vanadyl (IV) bis(acetylacetonate) and D-penicillamine neutral pH [25] is a complex with a rather large ligand by joining D-penicillamine with acetylacetonate ligand and complexation at weak alkali and strong alkali has different thermodynamic entities, so it is likely that the formation constants of the products of VO(acac) with D-penicillamine at pH = 7.00 and 7.50 are independent of ionic strength but a Debye–Huckel-type equation was established for the dependence of the formation constant on ionic strength at pH = 10.0
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