Hydrothermal Synthesis, Structural Investigation and Characterization of an Organic-inorganic Hybrid, [Co(BIIM)3]2H[BW12O40]•7H2O

An organic-inorganic hybrid based on alpha-Keggin-typed [BW12O40](5-) anionic cluster, [Co(BIIM)(3)](2)H[BW12O40]center dot 7H(2)O (BIM = 2,2'-biimidazole), was hydrothermally synthesized and structurally characterized by thermogravimetric analysis, IR and UV spectra. The title compound crystallizes in monoclinic, space group P2(1)/n with a = 12.3490(10), b = 33.270(3), c = 18.9660(16) angstrom,16 = 105.9950(10), V = 7490.5(11) angstrom(3), C36H50BCo2N24O47W12, M-r = 3905.80, D-c = 3.451g/cm(3), mu(MoK alpha) = 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 > 2 sigma(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 center dot center dot center dot 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-O-terminal(imidazole)...pi (ring) interactions which cooperate with the classical N-H center dot center dot center dot O hydrogen bonds to stabilize the structural packing.