Syntheses, Structures And Characterization Of Transition Metal Complexes Of 2, 2'-biimdazole And Its Derivatives

The transition metal coordination compounds with imidazole and its derivatives are more and more important as their various structures and extensive uses in the field of catalysis, bioactivity, and material etc. Therefore, 2,2'-biimidazole, its methyl derivatives ligands and their transition metal complexes in the paper have been synthesized and characterized.The main work is as follows:1. The 2,2'-biimidazole (H₂biim) ligand and eight corresponding complexes with transition metal ion Zn²⁺, Mn²⁺, Cd²⁺, Co²⁺, Ni²⁺and Cu²⁺ have been designed and synthesized, in which eight single crystals were abotaind. These complexes are characterized by IR spectrum, UV-Vis spectrum, thermal analysis and structural analysis. The structural analysis of complexes show that H₂bbiim usually behaves as a chelating bidentate ligand for it's a rigidity group, and mononuclear compounds were often obtained. Furthermore, H₂biim can act as a donor in hydrogen bonding interactions, in this case, two oxygen atoms of a carboxylate group can join directly to the N-H donors via a charge-assisted heteromeric hydrogen-bonded synthon of R₂²(9), extending into multidimensional networks in definite directions. In addition to, there also exist hydrogen bonding interactions between the N-H donors of H₂biim and haloid atoms or carbon atoms. Moreover, there are strong Ï€-Ï€ stacking interaction in adjacent imidazoles, which resulted in two-dimensional network structure so much as three-dimensional stereo structure. The TG studies of the complexes synthesized under hydrothermal condition are more stable than those under common condition.2. The N,N'-dimethyl-2,2'-biimidazole ligand(Me₂biim) and six corresponding complexes with transition metal ion Ag⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ have been designed and synthesized on a basis of H₂biim. These complexes are characterized byIR spectrum, UV-Vis spectrum and molar conductance. A new helix coordination polymer [Zn(u-Me2biim)Cl2]n has been obtained under hydrothermal condition and was characterized by thermal analysis, photoluminescence spectrum and single crystal structural analysis additionally. The results indicate that the Me2biim ligand form dinuclear and polymeric structures with unidentate coordination, since the methyl steric requirements force the two imidazole rings out of coplanarity. Free Me2biim exhibits a weak emission of fluorescence. A comparison of the fluorescence spectra of the Me2biim ligand and its Zn complex demonstrate that the emission of fluorescence was strongly enhanced in the Zn compound. Thermal analysis indicates that the Zn complex is stable until to 355 "C, and then the ligand start to decompose step by step.3. The N-methyl-2,2'-biimidazole ligand (MeHbiim) and two corresponding complexes with transition metal ion Cd2+ and Mn2+ have been synthesized. These complexes are characterized by IR spectrum, UV-Vis spectrum and Molar conductance. Thereinto, a novel coordination polymer [Cd3(MeHbiim)2(u-tere)3]n has been obtained under hydrothermal condition in the first time and was characterized by thermal analysis, photoluminescence spectrum and structural analysis additionally. The structural analysis indicates that the MeHbiim behaves as a chelating bidentate ligand similar to the H2biim ligand except the weak rigidity. And hydrogen bonding interactions between the N-H donor of MeHbiim and the charge acceptor atoms is still existed. Due to the variety of the coordinated mode of the terephthalate, a linear trinuclear Cd polymer with 3-D topology was formed. Photoluminescence spectrum showed highly enhanced fluorescence intensity in Cd polymer comparing to free MeHbiim ligand.