A one-dimensional chain of manganese(II) bridged peroxomolybdate isolated from an aqueous Mn-polymolybdate-H 2 O 2 system.

A new manganese(II)-peroxomolybdate complex, Cs 4 [Mn(OH 2 ) 2 (Mo 7 O 22 (O 2 ) 2 )]·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 [Mo 7 O 22 (O 2 ) 2 ] 6- units were linked by Mn(II) ions to form a one-dimensional infinite chain of [Mn(OH 2 ) 2 (Mo 7 O 22 (O 2 ) 2 )] n 4 n - , which represents a unique structure with the coexistence of the oxidant-reductant pair O 2 2- /Mn 2+ . The interconversion between [Mn II (OH 2 ) 2 (Mo 7 O 22 (O 2 ) 2 )] 4- and [MnMo 9 O 32 ] 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-H 2 O 2 system. In the oxidation process of 3,3',5,5'-tetramethylbenzidine and ortho -phenylenediamine by H 2 O 2 , Cs-1 shows notable activity as an enzyme mimetic catalyst.