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Three novel coordination polymers have been synthesized via hydrothermal reactions at different temperatures, namely [Cu2(H2tcbi)(H2O)4] (1), [Cd3(H3tcbi)2(H2O)6]·2H2O (2) and [Ca(H4tcbi)(H2O)2] (3) (H6tcbi = 4,4′,5,5′-tetracarboxyl-2,2′-biimidazole). This is the first report on complexes of the Hntcbi ligand. Single crystal X-ray analyses reveal that they have rich structural chemistry, ranging from one-dimensional (1), to two-dimensional (2 and 3). Three different coordination modes of the H6tcbi ligand, μ2, μ3 and μ4, have been observed. The coordination geometries of the metal sites vary from five-coordinate square pyramidal, six-coordinate octahedral to seven-coordinate pentagonal bipyramidal. The H6tcbi ligand in complexes 1, 2 and 3 is tetra-deprotonated to H2tcbi4−, tri-deprotonated to H3tcbi3− and bi-deprotonated to H4tcbi2−, and coordinates to the metal ions as a tetradentate, pentadentate and pentadentate ligand respectively, resulting in the formation of 1D, 2D and 2D coordination polymers. Photoluminscent investigation of complexes 2 and 3 shows intense blue and green fluorescent emissions respectively.

The novel three-dimensional chiral framework of the four-coordinate zinc complexes, [Zn 4 (biim) 3 (ina) 2 ] ( 1a and 1b ) (H 2 biim = 2,2′-biimidazole, ina = isoniconate), has been prepared via hydrothermal reaction. X-ray single crystal diffraction analysis shows the biim 2− in title complexes acts as a tetradentate ligand and links four different Zn 2+ ions. Spontaneous chiral resolution occurs in solvo-thermal reaction, which was confirmed by solid-state circular dichroism spectra. Photoluminescent spectra of compound 1 exhibit an intense blue emission at 440 nm.