The syntheses, crystal structures, and characterizations of two MnII/III-sandwiching polyoxometalate complexes based on [α-SeW9O33]8− units

Abstract

Two sandwich-type polyoxometalates (POM) based on [α-SeW9O33]8− building blocks, K8[{MnII(H2O)}2(WO)(SeW9O33)2]·12H2O (1) and K6[{MnIII(H2O)}2(WO)(SeW9O33)2]·18H2O (2), have been synthesized and characterized by elemental analyses, IR, diffuse reflectance UV–vis-NIR spectra, TG, X-ray photoelectron spectroscopy, and single-crystal X-ray diffraction. Electrochemical properties and photocatalytic activities have also been investigated. Single-crystal X-ray diffraction analysis shows that the polyoxoanions of 1 and 2 have similar sandwich structures composed of [α-SeW9O33]8− units except for different oxidation states of Mn centers (II for 1, III for 2). Compound 2 is the first high-valent trinuclear-manganese (III)-substituted [α-SeW9O33]8−-based POM. Cyclic voltammograms of 1 and 2 show irreversible redox processes for Mn2+ and Mn3+, respectively. Compound 2 has better photocatalytic properties with photocatalytic degradation of Rhodamine-B (RhB) compared to 1.