Syntheses of two new hybrid compounds based on Keggin polyoxotungstates: The use of rigid and flexible ligands

Through using rigid and flexible bis(pyridine) ligands, two new Keggin POM-based hybrid compounds: [Cu(bipy)]2[H2SiW12O40]·2H2O (1) and [Cu(bpp)2][H2PW12O40]·2H2O (2) (bipy = 4,4′-bipyridine and bpp = 1,3-bis(4-pyridyl)propane) have been synthesized and characterized by routine methods. In compound 1, each rigid bipy molecule links two Cu ions into an unbent Cu–bipy coordination polymeric chain, which are further covalently connected by SiW12 clusters resulting in a ladder-like chain. In compound 2, the flexible organic ligand bpp with (CH2)3 spacer is used. The PW12 cluster as a template is wrapped by two “S”-style [Cu(bpp)2]+ fragments in a pseudo-parallelogram grid. Furthermore, these grids are fused together by sharing [Cu(bpp)2]+ fragments resulting in a 1D chain. Also, the electrochemical properties of these two compounds have been studied in the paper.