摘要:
The combination of the polydentate ligand 2-(1H-imidazol-1-yl) acetic acid (Hima) with metal ions (Pb2+, Li+, Zn2+, Cd2+, Fe2+ and Co2+) leads to seven different coordination polymers: [Pb-3(imaH)(2)Cl-6](n) (1, layer), [Pb(ima)(2)(NO3)(2)](n) (2, chain), [Li2H(ima)(2)(H2O)(2)Cl](n) (3, chain), [Zn(imaH)(ima)Cl](n) (4, chain), [Cd(imaH) Cl-2](n) (5, chain), and [M(ima)(2)]n (6, M = Fe; 7, M = Co; layer). All compounds were characterized by FT-IR, elemental analysis and TG analysis, and their structures were determined by single crystal X-ray diffraction. According to the structural analysis, compound 1 shows a [Pb3Cl6] layer; compounds 2-4 show an infinite chain, but they were connected with imaH or ima bridges, respectively; compound 5 also has an infinite chain constructed of double chloride bridges; and compounds 6 and 7 exhibit layers without chloride ions involved. In these compounds, the ligand adopts two kinds of forms (anion, ima or zwitter-ion, imaH) and shows diverse modes of coordination. More interestingly, chloride as the second anion participated in the structural architecture based on its different affinities with metal ions. Solid-state room temperature luminescence spectra revealed that emission bands of compound 1 were located at 455 nm, compound 4 at 425 nm, and compound 5 at 550 nm (lambda(ex) = 390 nm), which is mainly assigned to the Ligand-Metal Charge Transfer (LMCT). (c) 2012 Elsevier Ltd. All rights reserved.