Solvothermal synthesis, crystal structure and photoluminescence properties of four Cd(II) coordination polymers with different topological structures

Solvothermal reactions of tetrabromoterephthalic (H(2)tbtpa) acid and different bis-imidazoles with cadmium nitrate provided four new Cd(II) coordination polymers (CPs), namely, {[Cd(bip)(tbtpa)]center dot H2O}(n) (1), {[Cd-2(bibp)(tbtpa) 2(H2O)(4)]center dot H2O}(n) (2), {[Cd(1,2-mbix)(tbtpa)]center dot H2O}(n) (3) [Cd(1,2-mbix)(tbtpa)](n) (4), (bip = 1,4-di(1H-imidazol-1-yl) benzene, bibp = 1,1'-(2,5-dimethyl-1,4-phenylene) bis(1H-imidazole), 1,2-mbix = 1,2-bis((2-methyl-1H-imidazol-1-yl) methyl) benzene, H(2)tbtpa = tetrabromoterephthalic acid). All of the compounds have been structurally characterized by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric analyses (TGA). Single crystal X-ray diffraction analysis reveals that compound 1 exhibits a 3D diamond-type (dia, 66) framework of 3-fold interpenetration. Compound 2 displays a noninterpenetrated 3D network with the classical pcu topology. Compound 3 exhibits a polyrotaxanelike 2D + 2D /2D layer with 44-sql topology and the 2D sheets further formed a 3D framework by p/p interaction. Compound 4 is a 2D 44-sql network and the adjacent 2D networks are packed parallel in a /ABAB/fashion. Moreover, the thermal stability and photoluminescence properties of the compounds were investigated.