Construction and Properties of Six Metal-Organic Frameworks Based on the Newly Designed 2-(p-Bromophenyl)-Imidazole Dicarboxylate Ligand

The newly designed organic ligand 2-(p-bromophenyl)-1H-imidazole-4,5-dicarboxylic acid (p-BrPhH3IDC) has been successfully prepared and its coordination features were explored. By the reactions of p-BrPhH3IDC with main group or transition metals, six metal-organic frameworks (MOFs), namely, [Ca(p-BrPhHIDC)(H2O)(2)](n) (1), [Sr(p-BrPhHIDC)(H2O)](n) (2), [Zn(p-BrPhHIDC)(H2O)](n) (3), {[Co(p-BrPhH2IDC)(2)]center dot 2H(2)O}(n) (4), [Cd-1.5(p-BrPhHIDC)(p-BrPhH2IDC)(H2O)](n) (S), and {[Cd-2(p-BrPhHIDC)(2)(4,4'-bipy)]center dot 4H(2)O}(n) (4,4'-bipy = 4,4'-bipyridine) (6) have been synthesized under hydro(solvo)thermal conditions. X-ray single-crystal analyses reveal that they have rich structural chemistry ranging from one-dimensional (ID) (3), two-dimensional (2D) (1, 2, 4, and 5) to three-dimensional (3D) polymers (6). Furthermore, the existence of intermolecular hydrogen bonds and/or pi center dot center dot center dot pi stacking interactions between the aromatic groups supplies the additional stabilization for the solid-state supramolecular structures of polymers 3, 4, and S. The solid-state photoluminescence properties of the polymers 1-6 have been investigated as well.