Assembly multi-dimensional CdII coordination architectures based on flexible bis(benzimidazole) ligands: Diversity of their coordination geometries and fluorescent properties

Abstract

Based on three structurally related flexible bis(5,6-dimethylbenzimidazole) ligand, five novel metal–organic CdII coordination architectures: from 0D to 3D structures CdII complexes have been hydrothermally synthesized and structurally characterized, namely, Cd2I4(L1)2 (1), [CdCl2(L1)]n (2), [CdCl2(L2)]n (3), {[Cd(chdc)(L2)0.5]·H2O}n (4), {[Cd(pydca)(L3)0.5(H2O)2]·H2O}n (5) (where L1=1,2-bis(5,6-dimethylbenzimidazole)ethane, L2=1,3-bis(5,6-dimethylbenzimidazole)propane, L3=1,4-bis(5,6-dimethylbenzimidazole)butane, H2chdc=1,4-cyclohexanedicarboxylic acid, H2pydca=pyridine-2,6-dicarboxylic acid). A discrete binuclear [2+2] metallomacrocycles cadmium(II) complex of 1 is 0D, 3 and 5 exhibit one-dimensional helical and zigzag chain structures, respectively. 4 Forms a 2D layer with sql net topology bridged by carboxylate anion and L2, while 2 is an overall 3D array with the diamond topology (dia). In these complexes, the influences of anions coordination on the framework formation were observed and discussed. These results indicate the spacer length of the ligands and anions play important roles in controlling the diversity structural topologies of such metal–organic coordination architectures. The thermogravimetric analyses, X-ray powder diffraction and solid-state luminescent properties of the complexes have also been investigated.