Keggin polyoxometalate-templated chair-like heptanuclear silver complex

Two isostructural Keggin-templated compounds containing a chair-like heptanuclear silver complex, [{Ag7(Hbtz)2(btz)4}{PM12O40}]·H2O (M = W, 1; Mo, 2) (Hbtz = benzotriazolate), have been hydrothermally synthesized and characterized by routine methods and single crystal X-ray diffraction. In the compounds 1 and 2, the Hbtz ligands present two types of coordination modes. A pentameric silver chain with two kinds of Ag⋯Ag weak interactions exists in the heptanuclear silver complex. The heptanuclear silver cations connect the polyoxoanions PM12O403− to a two-dimensional layer, and the adjacent layers are fused together by the pseudo wave-like chains, H-bonds and AgI–π interactions, constructing a three-dimensional net. Furthermore, electrochemical properties have been studied for compounds 1 and 2 and the two compounds display excellent electrocatalytic activities to the reduction of nitrite.