Two unique hydroxyl bridged lanthanide polymers incorporating mixed carboxylate ligands: Syntheses, structures, luminescence and magnetic property

Abstract Two lanthanide–organic coordination polymers incorporating both substituted imdazole dicarboxylate and benzene monocarboxylate auxiliary ligand, namely, {[Gd 2 (μ 3- OH)(pimda)(imba) (H 2 pimda) H 2 O]·2H 2 O} n ( 1 ) and {[Tb 2 ((μ 3- OH)(pimda)(imba) (H 2 pimda) H 2 O]·2H 2 O} n ( 2 ) (H 3 pimda = 2-propyl-1H-imidazole-4,5-dicarboxylic acid and H 2 imba = 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 [Ln 4 pimda 2 ] 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.