Extended structure constructed from {Co 7 } cluster-containing sandwich-type polyoxometalate

Abstract We report a new 2D layer-like network composed of Co 7 cluster-containing sandwich-type polyoxometalate, Li 10 Na 2 [Co(H 2 O) 3 (CH 3 COO)] 2 {[Co 7 (H 2 O) 4 (OH) 2 (Ale) 2 ][PW 9 O 34 ] 2 }·20H 2 O ( 1 ) {H 5 Ale = Alendronic acid}, which was synthesized by the conventional aqueous solution method. Single-crystal X-ray diffraction analysis reveals that 1 crystallizes in the monoclinic P 2(1)/n space group with unit cell a  = 12.5391 (1) A, b  = 25.2531 (2) A, c  = 22.0462 (2) A, β  = 97.728(1)°, Z  = 2, V  = 6917.55 (10) A 3 . This compound was further characterized by powder X-ray diffraction (PXRD), IR spectra and thermogravimetric (TG) analyses to confirm its structure and composition. As a result, polyoxoanion in 1 consists of two { A -PW 9 O 34 } 9− units, which are fused together by a {Co 7 (H 2 O) 4 (OH) 2 (Ale) 2 } { Co 7 } cluster into a sandwich-type structure. In the { Co 7 } cluster, all the Co 2+ ions are connected together by two Ale ligands and two OH groups into the hepta-nuclear cobalt cluster { Co 7 }. Further, the sandwich-type polyoxoanions are connected together by two {CH 3 CO 2 Co(H 2 O) 3 } units, resulting in the first 2D layer-like structure consisting of Co 7 -containing sandwich polyoxoanion. Electrochemical and electrocatalytic studies reveal that 1 exhibits good electrocatalytic activity toward the reduction of H 2 O 2 in neutral aqueous solution.