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Syntheses, Structures, and Photoluminescence of Zinc(II) Coordination Polymers Based on Carboxylates and Flexible Bis-[(pyridyl)-benzimidazole] Ligands

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journal contribution
posted on 03.11.2010, 00:00 by Hai-Yan Liu, Hua Wu, Jian-Fang Ma, Ying-Ying Liu, Bo Liu, Jin Yang
Six coordination polymers based on three related flexible bis-[(pyridyl)-benzimidazole] ligands and different carboxylates, namely, [Zn2(m-BDC)2(L1)]·2H2O (1), [Zn2(p-BDC)2(L1)(H2O)2] (2), [Zn2(m-BDC)2(L2)]·2.25H2O (3), [Zn2(p-BDC)2(L2)]·CH3OH (4), [Zn2(m-BDC)2(L3)]·2H2O (5), and [Zn2(p-BDC)2(L3)]·2CH3OH (6), where L1 = 1,1′-(1,4-butanediyl)bis[2-(2-pyridyl)benzimidazole], L2 = 1,1′-(1,6-hexanediyl)bis[2-(2-pyridyl)benzimidazole], L3 = 1,1′-(1,10-decanediyl)bis[2-(2-pyridyl)benzimidazole], m-BDC = m-benzenedicarboxylate anion, and p-BDC = p-benzenedicarboxylate anion, have been synthesized under solvothermal conditions. Their structures have been determined by single crystal X-ray diffraction analyses and further characterized by elemental analyses and infrared (IR) spectra. Compound 1 shows a one-dimensional (1D) double chain which extends into a two-dimensional (2D) supramolecular sheet by π−π interactions. Polymers 24 display similar 2D layer structures with 3-connected 63 topologies. In 2 and 3, the adjacent layers are further connected through π−π interactions to form three-dimensional (3D) supramolecular structures. However, in 4, two identical layers penetrate each other in parallel modes to give a 2-fold parallel interpenetrating net. Compounds 5 and 6 show 2-fold interpenetrating networks with α-Po topological structures. A systematic structural comparison of these complexes indicates that the different lengths of the bis-[(pyridyl)-benzimidazole] ligands (L1−L3) are important for the formation of the different structures. In addition, the luminescent properties of L1−L3 and 16 have been studied in the solid state at room temperature.