Vanadium(III) interaction with adenine

The interaction of vanadium(III) trichloride with adenine in aqueous solutions was investigated. UV-Vis spectroscopy and potentiometry results proved that adenine stabilises the V(III) oxidation state and forms with vanadium trichloride weak monomeric and dimeric complexes in the 1.8-4.5 pH range, depending on the metal concentration. Conditional consecutive stability constants of monomeric and dimeric species were evaluated. They are slightly higher than hydrolysis constants, which suggests very complex equilibria in aqueous solutions of this system. At pH > 4.5 precipitation of hydrolysis mixed vanadium-adenine-OH products with unidentified elemental formulae occurs. A stable V(III) microcrystalline dimeric and/or polymeric compound with formula {H-2[VCl2(Ad(-))O]}(x) was isolated in solid phase from ethanol. The oxidation state of vanadium, + 3, and V(III) ion coordination by adenine molecule in the solid phase was confirmed by measurements of reflectance spectra, magnetic susceptibility measurements (mu = 2.5 BM V-1 in the 40- 300 K range) as well as IR spectra. (C) 2001 Elsevier Science Ltd. All rights reserved.