Hydrothermal Synthesis,Structural Investigation and Characterization of an Organic-inorganic Hybrid, [Co(BⅡM)_3]_2H[BW_(12)O_(40)]·7H_2O

An organic-inorganic hybrid based on α-Keggin-typed [BW12O40]5- anionic cluster, [Co(BⅡM)3]2H[BW12O40]·7H2O(BⅡM = 2,2′-biimidazole), was hydrothermally synthesized and structurally characterized by thermogravimetric analysis, IR and UV spectra. The title compound crystallizes in monoclinic, space group P21/n with a = 12.3490(10), b = 33.270(3), c = 18.9660(16) β = 105.9950(10)°, V = 7490.5(11) 3, C36H50BCo2N24O47W12, Mr = 3905.80, Dc = 3.451g/cm3, μ(MoKα) = 18.886 mm-1, F(000) = 6972, Z = 4, S = 1.004, the final R = 0.0404 and wR = 0.0914 for 14683 observed reflections(I 2σ(I)). The compound consists of two isolated [Co(BⅡM)3]2+ cations and one [BW12O40]5- anion, in which each Co2+ ion is coordinated by six N atoms from three BⅡM ligands displaying a regular CoN6 octahedron. These components are finally linked together via N–H···O(polyoxometalate and water) hydrogen bonds into a two-dimensional framework. Full investigation of the intermolecular interactions by Hirshfeld surface and fingerprint plots clearly indicates that there are rare W–Oterminal···πimidazole ring interactions which cooperate with the classical N–H···O hydrogen bonds to stabilize the structural packing.