Syntheses, Structures And Properties Of Coordination Complexes Based On An Unsymmetrical Ligand And Carboxylate Both Containing Nitrogen

The functional complexes built by benzimidazole and its derivatives present unique optical properties, catalytic properties or biological activity, and also possess the characteristics of polymer and composite macromolecule, as a result, increasing attention has been paid on this field in recent years. In this paper, we used an unsymmetrical N-heterocyclic compound 2-(1H-imidazole-l-methyl)-1H-benzimidazole(imb), in the existing of the second ligands succinic acid,1,3-Benzenedicarboxylic acid,1,2-Benzenedicarboxylic acid, 1,3,5-Benzenetricarboxylic acid or 1,2,4,5-Benzenetetracarboxylic acid (H2adi, 1,3-bdc,1,2-bdc, btc or dpa) to react with Zn(II) ions through hydrothermal syntheses technology, and obtained a series of zinc complexes:[Zn(imb)3]4·(NO3-)·H2O (1), [Zn(adi)2-(imb)·1.5H2O]n (2),{[Zn2(1,3-bdc)2-2(imb)2]·3H2O}n (3), [Zn2(1,2-bdc)2-2(imb)2]n (4), [Zn(btc)2(imb)2] (5),{[Zn4(dpa)2(imb)4]·4H2O}n (6). Crystal structures have been determined by single crystal X-ray diffraction:complex 1 is a tetranuclear structure, and the ligands coordinate with center Zn(II) ions by two different modes; based on 1, we obtained complex 2 by using of succinic acid,2 indicates three-dimensional structure through the intersecting of the two-dimensional networks; by using of 1,3-BDC and 1,2-BDC, we obtained complex 3 and 4, they display two dimensional layered structure and one-dimensional chain structure, respectively; complex 5 is a mononuclear structure; 6 indicates three-dimensional network structure. Otherwise, we used 2-(1H-imidazole-l-methyl)-1H-benzimidazole as the precursor to synthesize a new carboxylic ligand which possesses abundant coordination sites. We have obtained complex 7 which displays three-dimensional structure based on this carboxylic ligand, using hydrothermal syntheses technology.The investigation of fluorescent properties for the free ligand 2-(1H-imidazole-l-methy1)-1H-benzimidazole, carboxylic ligands and complexes 1-6 have been observed. The results show that the fluorescence intensity of the six complexes are significantly weaker than the ligand, and the existence of carboxylic ligands can not affect their fluorescence emission features. In addition, we also investigated the thermal properties for complexes 1-4 and 6. The results show that complexes 1-3 and 6 begin to decompose at low temperature and are less stable as the existence of radical groups, complex 4 possesses satisfactory thermal stability.