Structural Diversity and Properties of Six ZnII/CdII Coordination Polymers Based on an O-Bridged Semi-Rigid Bis-pyridyl-bis-amide and Different Dicarboxylates

Abstract

Six new coordination polymers [Zn2(L)(chdc)2]·2H2O (1), [Zn(L)(mip)]·3H2O (2), [Zn(L)(bdc)]·H2O (3), [Cd2(L)(chdc)2]·2H2O (4), [Cd(L)(mip)]·2H2O (5), and [Cd(L)(bdc)]·2H2O (6) (L = N,N′-bis(pyridine-3-yl)-4,4′-oxybis(benzoic) dicarboxamide, 1,4-H2chdc = trans-1,4-cyclohexanedicarboxylic acid, H2mip = 5-methylisophthalic acid, 1,3-H2bdc = 1,3-benzenedicarboxylic acid) have been synthesized from ZnII/CdII ions and L ligands in the presence of auxiliary dicarboxylates via hydrothermal or solvothermal reaction. The coordination polymers have been fully characterized by infrared spectroscopy, powder X-ray diffraction, thermogravimetric analyses, and single-crystal X-ray diffraction analysis. Complex 1 contains a 1D [Zn4(chdc)4]n wave-like chain, which is connected by the μ2-bridging ligand L, affording a 3,4-connected 2D polymeric network. Complexes 2 and 3 both possess similar 2D 4-connected square grid-like layers, which are based on Zn-carboxylates linear chains and left-handed [Zn(L)]n helix chains. The structure of complex 4 is very similar to that of 1. Complexes 5 and 6 demonstrate a similar 2D 3,5-connected channel-level network, which is constructed from a pair of Cd-carboxylates linear chains and 1D [Cd2(L)2]n cyclic chains. The effects of the central metal ions and different dicarboxylates on the formation and structures of the title coordination polymers have been discussed. In addition, the fluorescence and photocatalytic properties of the title complexes have been investigated.