Three new metal–organic complexes derived from N,N′-bis(3-pyridinecarboxamide)-1,2-ethane and polycarboxylate ligands: Synthesis, fluorescent and electrochemical properties

Three new metal–organic coordination polymers, [Cu2(3-dpye)(2,6-PDA)2(H2O)2] (1), [Cu2(3-dpye)(1,3,5-HBTC)2(H2O)3]·3H2O (2), [Cu(3-dpye)(1,3-BDC)(H2O)]·H2O (3), have been hydrothermally synthesized by using the flexible N,N′-bis(3-pyridinecarboxamide)-1,2-ethane (3-dpye) and different polycarboxylates [2,6-H2PDA = pyridine-2,6-dicarboxylic acid, 1,3,5-H3BTC = benzene-1,3,5-tricarboxylic acid, 1,3-H2BDC = benzene-1,3-dicarboxylic acid] as mixed ligands, and characterized by elemental analyses, IR, TG and single crystal X-ray diffraction. In complex 1, Cu(II) ions are bridged by 3-dpye to form dinuclear units, which are linked by hydrogen bonding interactions to construct a two-dimensional (2D) supramolecular layer. Complex 2 is a 2D coordination network with a new (3·72)2(3·73·82) topology based on two kinds of 1D polymeric chains: Cu-3-dpye chain and Cu-1,3,5-HBTC chain, and the adjacent 2D layers are packed into a 3D supramolecular structure through hydrogen bonding interactions. Complex 3 exhibits a 3D polymeric framework with threefold interpenetrating 4-connected (65·8) CdSO4-like topology, which represents the first example of 3D coordination polymers constructed from 3-dpye and aromatic polycarboxylate ligands. 3-dpye ligands adopt a μ2-bridging mode in 1 and 3 (via ligation of two pyridyl nitrogen atoms) and a μ3-bridging coordination mode in 2 (via ligation of two pyridyl nitrogen atoms and a carbonyl oxygen atom), which play an important role in the construction of final polymeric structures. The polycarboxylates with different coordination atoms also show obvious effect on structures of the title complexes. In addition, the electrochemical behaviors and the fluorescence properties of complexes 1–3 have been reported.