Structurally characterised vanadium(v)-substituted Keggin-type heteropolysulfates [SVM11O40]3− (M = Mo, W): voltammetric and spectroscopic studies related to the V(v)/V(iv) redox couple

Abstract

Structures of the n-tetrabutylammonium salts of [SVM11O40](3-) (M = Mo, W) have been determined by X-ray crystallography and exhibit 3D networks with the V atom disordered over several sites. The cyclic voltammetric behavior of SVM11 in neutral and acidified acetonitrile solutions also has been investigated with respect to the V(V)/V(IV) couple. Results have been interpreted in conjunction with data provided by (51)V NMR spectroscopy on the oxidized V(V) form and by EPR spectroscopy on the reduced V(IV) form. Based on mechanistic details inferred from these studies, simulations of the cyclic voltammograms have been undertaken and results compared with experimental data in acidic media (two protonated forms) in order to provide estimates of equilibrium and kinetic parameters. For the V(V)/V(IV) couple in the series [XVM11O40](n-) (X = Si,Ge,P,As,S; M = Mo,W), the reversible potentials in neutral acetonitrile linearly depend on the total charge of the vanadium-substituted polyoxometalates, similar to the dependence previously reported for the non-substituted parent Keggin polyoxometalates [XM12O40](m-).

New Electrochemical Evaluation of the Antioxidant Capacity of Beverages with Polyoxometalates as Redox Probes

“…Vanadium-substituted Keggin-type POMs, n-(X = Si, Ge, P, As, S; M = Mo, W), exhibit higher redox potentials than the corresponding parent non-substituted POMs, [XM12O40] n-. 29,30 In addition, heteropolytungstates are generally more rigid than heteropolymolybdates for hydrolysis. These electrochemical and chemical properties imply that these compounds would react smoothly and stably with antioxidants.…”

“…[25][26][27][28] Recently, we investigated the detailed redox mechanisms of vanadiumsubstituted POMs in CH3CN. 29,30 In general, the redox potentials of POMs are more positive than those of many metal complexes, and POMs are very redox-stable. This property implies that POMs can be used as sensitive probes to evaluate antioxidant activity via electrochemical methods because antioxidants, depending on their activity, can reduce some parts of POMs.…”

Vanadium‐Substituted Tungstosulfate Polyoxometalates as Peroxidase Mimetics and Their Potential Application in Biosensing

“…The observed IR peaks were identical with the reported data. [25,26] Cyclic voltammograms of 0.5 mM SVW 11 and SV 2 W 10 were measured in CH 3 CN containing 0.1 M n-Bu 4 NPF 6 in the absence and in the presence of CF 3 SO 3 H. All of the first reduction processes for SVW 11 are due to V(V/IV). In the case of the SV 2 W 10 , two vanadium atoms were reduced at the same potential after addition of acid (Figure S2).…”

“…In the case of the SV 2 W 10 , two vanadium atoms were reduced at the same potential after addition of acid (Figure S2). [26]…”

Diversity of Polyoxometalate‐Based Copper Compounds Obtained from the Same Reaction System

“…The peak potentials of anodic waves II shows shifts of 0.12 V between CPE 1 and CPE 2 or CPE 4 (Table ); therefore, wave II may be a result of an overlap of the waves for the oxidation of copper(I) centres and the further oxidation of Mo V centres. In this potential range, no redox peaks ascribed to vanadium should be observed, as it is present as a stable V V species in acidic solution . The anodic peak III appears only for CPE 2 and CPE 4 at a high overpotential as a one‐electron oxidation.…”