名称:
Syntheses, crystal structures and properties of metal complexes with 4,4′,5,5′-tetracarboxyl-2,2′-biimidazole
摘要:
Three novel coordination polymers have been synthesized via hydrothermal reactions at different temperatures, namely [Cu-2(H(2)tcbi)(H2O)(4)] (1), [Cd-3(H(3)tcbi)(2)(H2O)(6)]center dot 2H(2)O (2) and [Ca(H(4)tcbi)(H2O)(2)] (3) (H(6)tcbi = 4,4',5,5'-tetracarboxyl-2,2'-biimidazole). This is the first report on complexes of the H(n)tcbi 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 H(6)tcbi ligand, mu(2), mu(3) and mu(4), 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 H(6)tcbi ligand in complexes 1, 2 and 3 is tetra-deprotonated to H(2)tcbi(4-), tri-deprotonated to H(3)tcbi(3-) and bi-deprotonated to H(4)tcbi(2-), 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. (C) 2013 Elsevier Ltd. All rights reserved.