A novel one-dimensional organic-inorganic polymer: synthesis and crystal structure of [{Ca(DMF)5}2SiMo12O40]η

A novel polyoxometalate-based organic-inorganic polymer [Ca(DMF)52SiMo12O40]η 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, P21/n, with a =1. 3379 (3),b = 1. 9796 (4), c = 1. 4574 (3) nm, β= 92.24(3)δ,V= 3. 8568 (13) nm3, Z = 2,R1= 0.083 andRw= 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-Od-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 (λ= 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 stages of weight loss and that the thermal stability of polyanion is better than that of H4SiMo12O40 · H2O.