Syntheses, structures and properties of five Cu(II) coordination polymers derived from semi-rigid bis-pyridyl-bis-amide and nitro-substituted aromatic carboxylates

Abstract

Five new coordination polymers (CPs) based on two semi-rigid bis-pyridyl-bis-amide ligands and different nitro-substituted carboxylates, namely [Cu(3,5-dnb)(μ2-OH)] (1), [Cu4(4-bpcc)2(3,5-dnb)6(μ3-OH)2(H2O)2] (2), [Cu(4-bpcc)2(5-Hnip)2] (3), [Cu3(4-bpcc)(5-nip)2(5-Hnip)(μ3-OH)(H2O)]·4H2O (4), and [Cu(3-bpcc)(5-nip)]·2H2O (5) (3,5-Hdnb=3,5-dinitrobenzoic acid, 5-H2nip=5-nitroisophthalic acid, 4-bpcc=N,N′-bis(4-pyridinecarboxamide)-1,2-cyclohexane, and 3-bpcc=N,N′-bis(3-pyridinecarboxamide)-1,2-cyclohexane), were synthesized under hydrothermal conditions and characterized by single crystal X-ray diffraction, elemental analysis, IR spectroscopy, TG analysis and powder X-ray diffraction. Complex 1 shows a 3D framework, which features a (3,5)-connected topology with the Schläfli symbol of {3·72}{32·75·83}. Complex 2 displays a 3D supramolecular structure based on the tetranuclear [Cu4(3,5-dnb)6(μ3-OH)2] clusters, while complex 3 presents a 3D supramolecular architecture with mononuclear Cu(II) subunits. Complex 4 was obtained at a higher pH value than that in 3, which exhibits a uninodal 5-connected 3D bnn framework constructed from 1D ladder-like chains and μ2-bridging 4-bpcc ligands. Complex 5 is a 2D (4,4)-network based on a 1D [Cu(3-bpcc)]n meso-helixe and a 1D [Cu(5-nip)]n zigzag chains. The bis-pyridyl-bis-amide ligands and nitro-substituted carboxylates, as well as pH show great influence on the formation and various structures of the title complexes. The fluorescent and electrochemical properties of the title complexes were investigated.