A novel one-dimensional organic-inorganic polymer:: synthesis and crystal structure of [{Ca(DMF)5}2SiMO12O40]n

A novel polyoxometalate-based organic-inorganic polymer [{Ca(DMF)(5)}(2)SiMo12O40](n), has been synthesized and characterized by elemental analysis, IR, UV and X-ray single-crystal structural analysis. The title compound crystallizes in a monocline lattice, P2(1)/n, with a = 1.3379(3), b = 1.9796(4), c = 1.4574(3) nm, beta = 92.24(3)degrees, V = 3.8568(13) nm(3), Z = 2, R-1 = 0.083 and Rw = 0.2065. The result of crystal structure analysis indicates that Ca2+ is surrounded by seven coordination oxygen atoms with pentagonal bipyramidal geometry and bridged with terminal oxygen atom of polyanion in the structure. The compound contains an unprecedented one-dimensional linear chain built by alternate polyanions and cationic units through Mo-O-d-Ca-O-Ca links in crystal. The IR spectra and X-ray crystallography analysis exhibit that there is a strong interaction between the polyanion and organic group in solid state. The electronic spectra (lambda = 200-500 nm) for the title compound dissolved in the mixed solvent of acetonitrile and water indicate that it is fully dissociated. The TGA/DTA study shows three stage's of weight loss and that the thermal stability of polyanion is better than that of H4SiMo12O40.H2O.