1D helical ZnII metal–organic polymers: Syntheses, structures and fluorescent properties

Hydrothermal reactions of 1,1′-(1,5-pentanediyl)bis-1H-benzimidazole (pbbm) with ZnCl2 afford two 1D helical metal–organic polymers {[ZnCl2(pbbm)] · (H2O)1/8}n (1) and {[Zn(pbbm)2] · Cl2 · (H2O)1/2}n (2). Polymer 1 features a 1D single helical architecture, whereas 2 possesses a 1D cationic double helical chain framework. Photoluminescence investigations reveal that both of them display strong emissions in the solid state at room temperature, which could originate from a ligand-to-ligand charge-transfer (LLCT) transition, as confirmed by the molecular orbital (MO) calculations.