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Paper
CrystEngComm, 2009, 11, 847 - 854, DOI: 10.1039/b819800d
Temperature- and solvent-controlled dimensionality in a zinc 6-(1H-benzoimidazol-2-yl)pyridinecarboxylate system
Xiao-Ming Lin, Hua-Cai Fang, Zheng-Yuan Zhou, Li Chen, Jing-Wei Zhao, Shi-Zheng Zhu and Yue-Peng Cai
Several 0D, 1D, and 3D metal–organic hybrid frameworks of ZnII have been synthesized by using the asymmetric ligand 6-(1H-benzoimidazol-2-yl)pyridinecarboxylic acid (HL) with control of the temperature and solvent in a solvothermal synthesis technique. In DMF, the structure at room temperature confirms that the resulting compound Zn(L)2·2(H2O) (1) is the 0D mononuclear structure, above
80 °C, C–N bond cleavage of partial DMF molecules induces the formation of the 1D chain-like compound {[Zn(L)(HCOO)]·2(H2O)}n (2), but on warming up to 120 and 160 °C, due to the decomposition of a large number of DMF molecules, the same reaction, respectively, gives two 3D metal–organic coordination polymers with 3D channels reported previously {[Zn(HCOO)3]-·[H2N(CH3)2]+}n (3) and [Zn(HCOO)2]n (4), in which the 3D channels of 3 contain guest [H2N(CH3)2]+ motifs, while at high temperature the 3D channels of 4 are an open stable system without any guest molecules. Replacing DMF in the above reaction by ethanol or acetonitrile, only 0D compound 1 is obtained in the range from room temperature to 160 °C. However, the same reaction in DMSO provides a 1D wave-like compound {[Zn(L)(DMSO)]·(ClO4)·H2O}n (5), in which the solvent DMSO molecule coordinates to the central metal ZnII ion. Furthermore, in three new complexes 1, 2 and 5, through 
stacking and hydrogen bonding interactions, 3D supramolecular networks are assembled. It is worth noting that the existence of the twelve-membered cyclic water–perchlorate dimers [(ClO4)(H2O)]22- with chair-conformation in the solid state of 5 not only increases the stability of the supramolecular structure, but also results in a stronger fluorescence signal compared with ligand HL, 1 and 2.
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