Two-dimensional extended (4,4)-topological network constructed from Tetra-NiII-Substituted sandwich-type keggin polyoxometalate building blocks and NiII-organic cation bridges

Three novel inorganic-organic composite polyoxotungstates {[Ni(dap)(2)(H2O)](2)[Ni(dap)(2)](2)[Ni-4(Hdap)(2)(alpha-B-HSiW9O34)(2)]}center dot 7H(2)O (1), {[Ni(dap)(2)(H2O)](2)[Ni(dap)(2)](2)[Ni-4(Hdap)(2)(alpha-B-HGeW9O34)(2)]}center dot 6H(2)O (2), and {[Ni(dap)(2)(H2O)](2)[Ni(dap)(2)](2)[Ni-4(Hdap)(2)(alpha-B-PW9O34)(2)])center dot H2O (3) (dap = 1,2-diaminopropane) have been hydrothermally synthesized and characterized by IR spectra, optical diffuse reflection spectroscopy, elemental. analysis, thermogravimetric analysis, and single-crystal X-ray diffraction. Three polyoxotungstates all crystallize in the triclinic space group P (1) over bar, with a = 13.3613(4) angstrom, b = 13.9821(4) angstrom, c 17.0305(5) angstrom, alpha = 68.085(10)degrees, beta = 71.179(11)degrees, gamma = 87.876(14)degrees, Z = 1, R-1 = 0.0742, wR(2) = 0.1692 for 1, a = 13.338(3) angstrom, b = 13.978(3) angstrom c = 17.049(3) angstrom, alpha = 68.159(6)degrees, beta = 71.100(8)degrees, gamma = 87.683(9)degrees, Z = 1, R-1 = 0.0499, wR(2) = 0. 1061 for 2, and a = 13.3570(19) b 13.997(2) angstrom, c = 17.129(2) angstrom, alpha = 67.468(4)degrees, beta = 71.986(5)degrees, gamma = 88.698(6)degrees, Z = 1, R-1 = 0.0461, wR(2) = 0.1254 for 3. Three isostructural polyoxotungstates utilize the two-dimensional structures with inorganic-organic composite surfaces built up from tetra-Ni-II-substituted sandwich-type Keggin polyoxometalate building blocks and Ni-II-dap cation bridges, representing the first (4,4)-connected topological network in polyoxometalate chemistry. Magnetic susceptibility measurements indicate the occurrence of ferromagnetic coupling interactions within the Ni-II centers for 1 and 2.