Two lanthanide–organic coordination polymers incorporating both substituted imdazole dicarboxylate and benzene monocarboxylate auxiliary ligand, namely, {[Gd2(μ3-OH)(pimda)(imba) (H2pimda) H2O]·2H2O}n (1) and {[Tb2((μ3-OH)(pimda)(imba) (H2pimda) H2O]·2H2O}n (2) (H3pimda = 2-propyl-1H-imidazole-4,5-dicarboxylic acid and H2imba = 4-(1H-imidazole-1-ly) benzoic acid) have been obtained under the hydrothermal conditions, and have been structurally characterized by elemental analysis, IR spectrum and single X-ray diffraction. The polymers are isostructural, both crystallizing in the triclinic system, with space group of p-1. They display one dimensional (1-D) double-stranded ribbon chains based on hydroxyl-bridged [Ln4pimda2] tetranuclear unit as second building block, which are interlinked forming 2-D corrugated layer. The extensive hydrogen bondings further extend these 2-D lamellar networks into 3-D supramolecular architecture. The emission spectrum of polymer 1 exhibits ligand-to-ligand charge-transfer (LLCT) transition luminescence; polymer 2 shows characteristic f-f transition luminescence, which can be considered as a fluorescent molecular sensor for zinc(II) ions in environment. Variable-temperature magnetic susceptibility measurement reveals that multi-bridging fashion of carboxylic group in 1 results in depopulation of the stark levels for a single Gd(III) ion and/or possible antiferromagntic interactions between adjacent Gd(III) cations within the carboxylato bridged binuclear unit.
