A one-dimensional chain of manganese(II) bridged peroxomolybdate isolated from an aqueous Mn-polymolybdate-H2O2 system

A new manganese(II)-peroxomolybdate complex, Cs-4[Mn(OH2)(2)(Mo7O22(O-2)(2))]center dot 4.25H(2)O (Cs-1), was isolated from an aqueous solution containing manganese(II) sulfate, sodium heptamolybdate and hydrogen peroxide by the addition of Cs+ salt. Cs-1 was characterized by single crystal X-ray diffraction, thermogravimetry (TG), IR spectroscopy, powder X-ray diffraction (PXRD), cyclic voltammetry (CV) and ultraviolet-visible spectroscopy (UV-vis). The diperoxoheptamolybdate [Mo7O22(O-2)(2)](6-) units were linked by Mn(II) ions to form a one-dimensional infinite chain of [Mn(OH2)(2)(Mo7O22(O-2)(2))] n(4n-), which represents a unique structure with the coexistence of the oxidant-reductant pair O2(2-)/Mn2+. The interconversion between [Mn-II(OH2)(2)(Mo7O22(O-2)(2))](4-) and [MnMo9O32](6-) in the aqueous solution was monitored by UV-vis spectrophotometry. It indicates that 1 is a key intermediate during the redox cycle of Mn(II) and Mn(IV) in the Mn-polyoxometalate-H2O2 system. In the oxidation process of 3,3',5,5'-tetramethylbenzidine and ortho-phenylenediamine by H2O2, Cs-1 shows notable activity as an enzyme mimetic catalyst.

Automated summary

A new manganese(II)-peroxomolybdate complex, Cs-4[Mn(OH2)(2)(Mo7O22(O-2)(2))]center dot 4.25H(2)O (Cs-1), was synthesized by adding Cs+ salt to an aqueous solution containing manganese(II) sulfate, sodium heptamolybdate, and hydrogen peroxide. Cs-1 exhibits a unique structure with the coexistence of the oxidant-reductant pair O2(2-)/Mn2+. It serves as a key intermediate in the redox cycle of Mn(II) and Mn(IV) in the Mn-polyoxometalate-H2O2 system and shows notable activity as an enzyme mimetic catalyst in the oxidation process of 3,3',5,5'-tetramethylbenzidine and ortho-phenylenediamine by H2O2.