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

Six coordination polymers based on three related flexible bis-[(pyridyl)-benzimidazole] ligands and different carboxylates, namely, [Zn-2(m-BDC)(2)(L-1)]center dot 2H(2)O (I), [Zn-2(p-BDC)(2) (L-1) (H2O2] (2), [Zn-2(m-BDC)(2)(L-2)]center dot 2.25H(2)O (3). [Zn-2-(p-BDC)(2)(L-2)]center dot CH3OH (4), [Zn-2(m-BDC)(2)(L-3)]center dot 2H(2)O (5), and [Zn-2(p-BDC)(2)(L-3)]center dot 2CH(3)OH (6), where L-1 = L1'-(1.4-butanediyl)bis-[2-(2-pyridyl)benzimidazole] L-2 = 1,1'-(1,6-hexanediyl)bis[2-(2-pyridyl)benzimidazole], L-3 = 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 pi-pi interactions. Polymers 2-4 display similar 2D layer structures with 3-connected 6(3) topologies. In 2 and 3, the adjacent layers arc further connected through pi-pi 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-told interpenetrating networks with alpha-Po topological structures. A systematic structural comparison of these complexes indicates that the different lengths of the bis-[(pyridyl)-benzimidazolel] ligands (L-1-L-3) are important for the formation of the different structures. In addition, the luminescent properties of L-1-L-3 and 1-6 have been studied in the solid state at room temperature.