A zinc(II) coordination polymer based on a flexible bis(benzimidazole) ligand: synthesis, crystal structure and fluorescence study

A new one-dimensional Zn(II) coordination polymer, {[ZnCl2(BBM)]·CH3OH}n(2,2-(1,4-butanediyl)bis-1,3-benzimidazole [BBM]), has been obtained from the hydrothermal reaction of zinc chloride with the flexible bis-benzimidazole ligand BBM and characterized by single-crystal X-ray diffraction, elemental analysis, IR and UV–vis spectra. Structural analysis has revealed that the BBM ligand connects the Zn(II) atoms to form a square-wave chain, which is further extended into supramolecular layers through hydrogen bonds and π···π stacking interactions. Solid-state fluorescence investigations showed that the Zn(II) coordination polymer has an emission peak at 381 nm upon excitation at 330 nm, which is attributed to ligand-centered luminescence. It is only slightly red shifted as compared to the ligand but partially quenched due to the strong π···π stacking interactions.