Syntheses and crystal structures of two self-assembled dizinc(II) helicates with novel hydrazone linked polypyridyl ligands |
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Authors: | Hsien-Chang Kao Yi-Chun Wang Wen-Jwu Wang |
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Institution: | 1.Department of Chemistry,Tamkang University,Tamsui, New Taipei City,Taiwan |
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Abstract: | The rationally designed polydentate ligands, L 1 and L 2 , based on the pyridinyl moiety and the hydrazone fragment have been synthesized to coordinate zinc(II) ions. We utilize pyridine as a rigid core connecting two bipyridines as ligand building blocks with a hydrozone linker for the L 1 . The L 2 has a reversed design in which a bipyridine was used as a hinging-available building block of the ligand core, connecting two pyridazine arms with a hydrazone linker. Two novel helical dizinc(II) complexes were obtained by the reaction of L 1 and L 2 with zinc(II) perchlorate in acetonitrile. The structures of both helicates were confirmed by X-ray diffractometry. Single-stranded helicate Zn 2 L 1 contains two zinc ions bridged by an oxygen atom. Except for the L 2 ligand, no other bridging species were found between the two zinc ions in the double-stranded helicate Zn 2 L 2 2 . The self-assembling process of helicate Zn 2 L 1 in solution state was studied by UV–Vis spectrometric titration experiments. The stepwise formation constants imply a slightly positive cooperative behavior for the formation of helicates. |
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