Three novel 1-H-benzimidazole-5-carboxylate-based nickel(II)/cobalt(II) coordination polymers: Synthesis, crystal structures, luminescent, and magnetic properties

摘要

Three 1H-benzimidazole-5-carboxylate (Hbic-)-based coordination polymers, {[Ni(H_2O)(Hbic)_2]·2H_2O} _n (1), {[Ni(H_2O)_2(Hbic)_2] ·3H_2O}_n (2), and {[Co_2(H _2O)_4(Hbic)_4]·4DMF·3H _2O}_n (3) were obtained by reactions of the ligand H _2bic and Ni~(II)or Co~(II) salts in the presence of different structure directing molecules. They were structurally characterized by single-crystal X-ray diffraction, IR spectra, elemental analysis, thermal stability, luminescent, and magnetic measurements. Structural analysis suggests that the three polymers exhibit a 2D (4, 4) layer for 1 and 1D linear double chains for both 2 and 3 due to the variable binding modes and the specific spatial orientation of the Hbic- ligand towards the different paramagnetic metal ions, which were further aggregated into different 3D supramolecular architectures by popular hydrogen-bonding interactions. Weak and comparable antiferromagnetic couplings mediating by Hbic- bridge are observed between the neighboring spin carriers for 2 and 3, respectively. Additionally, complexes 1-3 also display different luminescence emissions at room temperature due to the ligand-to-metal charge transfer.