Solvent Effects on Complexation of Dioxovanadium (V) with Glycine in Methanol-Water Mixtures

The formation constants of the species formed in the systems fr + glycine + dioxovanadium(V) + and H+ + glycine have been determined in aqueous solutions of methanol at 25 °C and constant ionicstrength, using spectrophotometric and potentiometric techniques. It was shown thatdioxovanadium(V) forms two mononuclear 1 : land 1:2 complexes with glycine. The formationconstants in various media were analyzed in terms of Kamlet and Taft's parameters. Single-parametercorrelation of the formation constants, 13 and 13122, versus a (hydrogen-bond donor acidity) and f3(hydrogen-bond accepter basicity) are poor in all solutions, except for le (dipolarity/polarizability), butmulti-parameter correlation represents significant improvement with regard to the single-parametermodels. Linear relationship are observed when logp and logf3 1,2 are plotted versus re. Finally, theresults are discussed in terms of the effect of solvent on complexation.