Stability investigation of some heteropolyoxotungstate and heteropolyoxomolybdate salts in buffer solutions

Abstract

Polyoxometalates (POMs) have shown a great potential of antitumor and antiviral activities; take into account, in this work we investigated the stability of a series of heteropolyoxotungstate-amino acids, heteropolyoxomolybdate-amino acids and the corresponding 12-heteropoly acids at different experimental conditions such as pH, buffer concentration, and the type of counter ion using UV-vis spectroscopy. Furthermore, the effect of tyrosine and ornithine were investigated as a counter ion, on the stability of POMs. The results indicated that degradation of these POMs in aqueous solutions follows pseudo-first order reaction kinetics according to the order of H 4SiW 12O 40 > H 3PW 12O 40 > H 4SiMo 12O 40 > H 3PMo 12O 40 for stability with respect to increasing of pH. The stability of POM increases in the presence of these amino acids. © 2012 Elsevier B.V.