Coordination site induced controllable assembly of metal-organic units in polyoxometalate-based hybrids

Two hybrid materials based on Keggin-type polyoxometalate, [Ag-4(mtrz)(4)(H2O)(2)(SiW12O40)] (1), [Ag-4(mtez)(5) (SiW12O40)] center dot H2O (2), (mtrz = 1-methyl-1,2,4-triazole, mtez = 1-methyl-1,2,3,4-tetrazole), have been hydrothermally synthesized and structurally characterized. Through the use of the azole ligands mtrz and mtez, compounds 1 and 2 with totally different metal-organic units are obtained. In 1, the mtrz ligands with N atoms in meta-positions induced the formation of chain-like metal-organic units, while in 2, the mtez ligands with adjacent N atoms induced the assembly of tetranuclear units. The SiW12 anions act as bridging linkers to evolve the structural dimensionality of the two title compounds into 20 network and 3D framework, respectively. (C) 2014 Elsevier B.V. All rights reserved.