Structural diversity of four coordination polymers based on asymmetric dicarboxylate: Effect of metal ions and N-donor ligands

Abstract

To determine the influence of metal ion and N-donor auxiliary ligands on the formation of metal–organic frameworks, four novel metal coordination polymers, [Cd(bdam)(phen)2]n (1), [Cd(bdam)(bpy)]n·nH2O (2), [Zn(bdam)(bpy)]n·nH2O (3) and [Ag4(bdam)2(dpe)]n (4) (H2bdam=benzophenone-2,4′-dicarboxylic acid, bpy=2,2′-bpyridine, phen=1,10-phenanthroline, dpe=1,2-(4-pyridyl)ethane) were synthesized and characterized. Complex 1 is 1D square-wave-like chain structure. Two phen ligands chelate to one cadmium atom in 1. 2 shows 1D ring chain based on dinuclear cadmium unit linked by (bdam)2− ions, while two 2,2′-bpy ligands coordinate one dinuclear cadmium unit. 3 forms a 1D right-handed helical chain. Different from the above complexes, 4 possesses a 2D network structure based on octanuclear silver clusters cross-linked by bdam2− ions and dpe ligands, in which there is significantly Ag⋯Ag interactions. The structural differences of 1 and 2 indicate that the subtle variations on N-donor ligands can greatly affect the coordination modes of (bdam)2− ion and the coordination geometries of CdII ion. The structural differences of 2, 3 and 4 indicate that metal ions also have great influence on the structures of the complexes. In addition, we have investigated the luminescence of 1–4 in the solid state at room temperature, revealing that the polymers are photoluminescent and their emissions are varied with the alteration of metal ions and N-donor ligands.