PUB - Publikationen an der Universität Bielefeld

Catalysis of electron transfer by a Cu-substituted wheel-type oxomolybdate cluster-anion, [(H4Cu5II)Mo-28(V) Mo-114(VI) O-432(H2O)(58)](26-), {Mo142Cu5}, (1), is demonstrated. Data provided include aqueous-solution chemistry (stability) studies of 1 and [Mo-28(V) (Mo114O432)-O-VI(H2O)(58)H-14](26-) ,{MO142}, (2), derivatives of the "plenary" {Mo-154 anion, [(Mo28Mo126O462)-Mo-V-O-VI(H2O)(70)H-14}(14-) (3). Combined use of cyclic voltammetry and UV-vis spectroscopy shows that, while both 1 and 2 appear to be stable in solution at pH 0.33 (0.5 M H2SO4), 1 is more stable than 2 at pH 3 (in 0.2 M Na2SO4). Cyclic voltammetric analysis in the presence of O-2 shows that I is an electrocatalyst for electron transfer to O-2. Bulk electrolysis of 1 in the presence of O-2 (ca. 1 mM) is used to assess catalyst stability under turnover conditions, and to demonstrate that the final product of electrocatalytic reduction is water, rather than H2O2. Finally, control experiments using 1, 2, and CuSO4 (no oxomolybdate-cluster present), show that catalytic activity is due to specific interaction(s) between Cu ions and the Mo-142 type oxomolybdate structure of 1.