Two new polyoxometalate-based hybrids: Structural transformation played by a secondary bridging ligand

Two new Keggin polyoxometalate-based compounds, [Ag-4(phnz)(6)(SiW12O40)] (phnz = phenazine) (1) and [Ag(phnz)(1.5)][Ag(phnz)(pz)][{Ag-2(phnz)(pz)(H2O)}(SiW12O40)] (2) (pz = pyrazine), have been hydrothermally synthesized. Compound 1 is a discrete cluster in which the [SiW12O40](4) (SiW12) anion symmetrically connects two dinuclear Ag-2(phnz)(3) fragments. All Ag-I in 1 adopt a trigonal geometry. By introducing the secondary bridging ligand pz into the above system, compound 2 was obtained. Compound 2 contains three kinds of silver complex subunits: [Ag-2(phnz)(pz)(H2O)](2+), [Ag-2(phnz)(3)](2+) and [Ag(phnz)(pz)](+). The first one extends to a wave-like chain with SiW12 anions as bi-dentate suspenders, and the last two are counter cations. Furthermore, Ag-I ions in 2 exhibit three kinds of coordination modes. Their electrochemistry properties have also been studied. (C) 2010 Elsevier B.V. All rights reserved.