The redox properties of heteropolytungstosilicates of transition metals Kn[SiM(H2O)W11O39] (M = Mn2+, Fe3+, Co2+, Ni2+, Zn2+, Cd2+) n solution were studied with polarog. and cyclic voltammetry, together with UV spectroscopy and XPS. The order of the polarog. half-wave potential (E1/2) of heteropoly anions was as follows: Ni2+ > Co2+ > Zn2+ > Fe2+ > Mn2+. The E1/2 values of heteropoly anions were correlated linearly with both the electronegativities of the transition metals, and the logarithm of the rate constants (log k) of the reaction of transition metal ions with hydrated electrons. The reduction mechanism and effects of transition metals on the redox properties of the heteropoly anions are discussed.

Key words: OXIDATION REDUCTION REACTION, REACTION MECHANISM, HETEROPOLYACID, POLAROGRAPHIC ANALYSIS, SILICATE P, X-RAY PHOTOELECTRON SPECTROMETRY, ANION, TRANSITION METAL COMPOUND, ELECTROCHEMICAL ANALYSIS, TUNGSTATE P