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

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)center dot nH(2)O (2), [Zn(bdam)(bpy)](n)center dot nH(2)O (3) and [Ag-4(bdam)(2)(dpe)](n) (4) (H(2)bdam = 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 bdam(2) 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 Cd-II 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. (C) 2015 Elsevier B.V. All rights reserved.