TY - JOUR

T1 - Studies on the redox turnover of polyoxometalates using potentiometric chemical sensors

AU - Rudnitskaya, Alisa

AU - Gamelas, Jose A.F.

AU - Evtuguin, Dmitry V.

AU - Legin, Andrey

PY - 2012/4/1

Y1 - 2012/4/1

N2 - Redox reactions of Keggin-type polyoxometalates (POM), [PV xMo 12-xO 40] (3+x)- (x = 1, 2), have been studied for the first time employing an array of potentiometric chemical sensors. Variations in the concentrations of vanadyl ions (VO 2+) during the redox reactions of POMs were followed in the real-time. Differences in the vanadyl concentration profiles observed during re-oxidation of di- and mono-substituted POMs allow us to infer principally different re-oxidation mechanisms for these compounds. At the beginning of the oxidation of [PV IV 2Mo 10O 40] 7- under air an instant release of VO 2+ (ca. 7%) from the coordination sphere of POM to the outside solution was detected. VO 2+ concentration decreased rapidly while oxidation proceeded indicating return of vanadyl back to the coordination sphere of [PV V 2Mo 10O 40] 5-. This finding indicates the participation of VO 2+ outside Keggin structure in the re-oxidation mechanism of di-substituted POM. No release of VO 2+ was detected during re-oxidation of [PV IVMo 11O 40] 5- by air oxygen in the presence of laccase (this POM is not oxidisable by air at low temperature and atmospheric pressure). Biocatalysis of [PV IVMo 11O 40] 5- oxidation may include activation of the molecular oxygen by the prosthetic group of laccase thus allowing the oxidation of V(iv) inside the Keggin structure of POM, i.e., without vanadyl release into the outside solution.

AB - Redox reactions of Keggin-type polyoxometalates (POM), [PV xMo 12-xO 40] (3+x)- (x = 1, 2), have been studied for the first time employing an array of potentiometric chemical sensors. Variations in the concentrations of vanadyl ions (VO 2+) during the redox reactions of POMs were followed in the real-time. Differences in the vanadyl concentration profiles observed during re-oxidation of di- and mono-substituted POMs allow us to infer principally different re-oxidation mechanisms for these compounds. At the beginning of the oxidation of [PV IV 2Mo 10O 40] 7- under air an instant release of VO 2+ (ca. 7%) from the coordination sphere of POM to the outside solution was detected. VO 2+ concentration decreased rapidly while oxidation proceeded indicating return of vanadyl back to the coordination sphere of [PV V 2Mo 10O 40] 5-. This finding indicates the participation of VO 2+ outside Keggin structure in the re-oxidation mechanism of di-substituted POM. No release of VO 2+ was detected during re-oxidation of [PV IVMo 11O 40] 5- by air oxygen in the presence of laccase (this POM is not oxidisable by air at low temperature and atmospheric pressure). Biocatalysis of [PV IVMo 11O 40] 5- oxidation may include activation of the molecular oxygen by the prosthetic group of laccase thus allowing the oxidation of V(iv) inside the Keggin structure of POM, i.e., without vanadyl release into the outside solution.

UR - http://www.scopus.com/inward/record.url?scp=84861453156&partnerID=8YFLogxK

U2 - 10.1039/c2nj21053c

DO - 10.1039/c2nj21053c

M3 - Article

AN - SCOPUS:84861453156

VL - 36

SP - 1036

EP - 1042

JO - New Journal of Chemistry

JF - New Journal of Chemistry

SN - 1144-0546

IS - 4

ER -