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 )]·2H 2 O ( 1 ), [Zn 2 ( p -BDC) 2 (L 1 )(H 2 O) 2 ] ( 2 ), [Zn 2 ( m -BDC) 2 (L 2 )]·2.25H 2 O ( 3 ), [Zn 2 ( p -BDC) 2 (L 2 )]·CH 3 OH ( 4 ), [Zn 2 ( m -BDC) 2 (L 3 )]·2H 2 O ( 5 ), and [Zn 2 ( p -BDC) 2 (L 3 )]·2CH 3 OH ( 6 ), where L 1 = 1,1′-(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 π−π interactions. Polymers 2 − 4 display similar 2D layer structures with 3-connected 6 3 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 (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.