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

摘要

Two new Keggin polyoxometalate-based compounds, [Ag_4(phnz) _6(SiW_(12)O_(40))] (phnz = phenazine) (1) and [Ag(phnz)_(1.5)][Ag(phnz)(pz)][{Ag_2(phnz)(pz)(H _2O)}(SiW_(12)O_(40))] (2) (pz = pyrazine), have been hydrothermally synthesized. Compound 1 is a discrete cluster in which the [SiW_(12)O_(40)]~(4-) (SiW_(12)) 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)(H_2O)]~(2+), [Ag2(phnz) _3]~(2+) and [Ag(phnz)(pz)]~+. The first one extends to a wave-like chain with SiW_(12)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.