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.