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

Two new Keggin polyoxometalate-based compounds, [Ag4(phnz)6(SiW12O40)] (phnz = phenazine) (1) and [Ag(phnz)1.5][Ag(phnz)(pz)][{Ag2(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 Ag2(phnz)3 fragments. All AgI 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: [Ag2(phnz)(pz)(H2O)]2+, [Ag2(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, AgI ions in 2 exhibit three kinds of coordination modes. Their electrochemistry properties have also been studied.