Role of aromatic dicarboxylates in the structural diversity of cobalt(ii) and copper(ii) coordination polymers containing a flexible N,N′-di(3-pyridyl)octanediamide ligand

Abstract

Six new transition metal coordination polymers, namely, [Co(1,2-BDC)(L)_1.5(H₂O)] (1), [Co(1,3-BDC)(L)(H₂O)₂]·H₂O (2) [Co(5-AIP)(L)_0.5(H₂O)]·2H₂O (3), [Cu(1,2-BDC)(L)] (4), [Cu(1,3-BDC)(L)(H₂O)]·3H₂O (5), and [Cu₂(5-AIP)₂(L)₂(H₂O)]·6H₂O (6) (L = N,N′-di(3-pyridyl)octanediamide, 1,2-H₂BDC = 1,2-benzenedicarboxylic acid, 1,3-H₂BDC = 1,3-benzenedicarboxylic acid, 5-H₂AIP = 5-aminoisophthalic acid), have been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. In compound 1, the adjacent Co^II ions are connected by L ligands to form a 1D chain with an alternating arrangement of L ligands and Co₂L₂ dinuclear loops. The 1,2-BDC anions coordinate with one Co^II ion in a bis(monodentate) chelate mode. Complex 2 shows a 2D (4⁴) grid network with the sql topology, which consists of the 1D zigzag [Co–L]_n chain and 1D linear [Co-1,3-BDC]_n chain. When 5-H₂AIP is used in compound 3, an interesting 2D terraced-type layer based on 1D [Co-5-AIP]_2n ladder-like chains and μ₂-bridging L ligands with 3,4-connected {6².10}{6} topology is formed. Under the similar conditions to compound 1, except that the cobalt(II) salt is replaced by a copper(II) salt, a 2D wave-like network 4 with 2,4-connected {6⁴.8.10}{6} topology is obtained. Compound 5 displays a 3D coordination polymeric architecture based on 1D [Cu-1,3-BDC]_n chains and [Cu–L]_n chains, which represents an intriguing 3-fold interpenetrating framework with CdSO₄-type topology. When 1,3-BDC is replaced by 5-AIP, another 3-fold interpenetrating 3D CdSO₄-type coordination framework for compound 6 is obtained, which is constructed from three types of 1D chains: [L^a–Cu–L^c]_n chain, [L^b–Cu–L^b]_n chain and [Cu-5-AIP]_n chain. The adjacent 1D chains for 1 and 2D layers for compounds 2, 3 and 4 are further extended by hydrogen bonding interactions to 3D supramolecular frameworks. The effect of dicarboxylates and central metals on the structures of the title complexes has been discussed. Furthermore, the electrochemical behaviors and solid state fluorescent properties for compounds 1–6 are investigated.