N-ethyl-4,4'-bipyridinium ZnX4 (X=Cl or Br) with N-ethyl-4,4'-bipyridinium Generated In Situ: Syntheses, Structures,Fluorescence and TDDFT Calculations

摘要

Two new zinc bipyridinium compounds, [N-ethyl-4,4′-bipyridinium][ZnX4](X = Cl(1) or Br(2)) with N-ethyl-4,4′-bipyridinium generated in situ, have been synthesized through solvothermal reactions and structurally characterized by single-crystal X-ray diffraction analyses. Both compounds are isostructural and crystallize in the P21/c space group of monoclinic system. Compound 1: a = 8.4397(5), b = 21.988(1), c = 8.8777(5) , β = 106.490(1)°, V = 1579.7(2) 3, C12H15Cl4N2 Zn, Mr = 394.43, Z = 4, Dc = 1.658 g/cm3, S = 1.068, μ(MoKα) = 2.218 mm-1, F(000) = 796, R = 0.0295 and wR = 0.0766. Compound 2: a = 8.4154(6), b = 22.844(2), c = 9.0308(7) , β = 106.026(1)°, V = 1668.6(2) 3, C12H15Br4N2 Zn, Mr = 572.27, Z = 4, Dc = 2.278 g/cm3, S = 1.033, μ(MoKα) = 11.038 mm-1, F(000) = 1084, R = 0.0427 and wR = 0.1175. Both of them are characteristic of an isolated structure with the zinc atoms locating at a tetrahedral environment. In both compounds, the N-ethyl-4,4′-bipyridinium2+ cations and ZnX42– anions interconnect together via hydrogen bonding interactions to construct a three-dimensional(3-D) supramolecular framework. Fluorescent studies reveal that both compounds exhibit a strong emission in the green region. In combination with the theoretical calculations, we can draw a conclusion that the emissions should result from ligand-toligand charge-transfer(LLCT) transition.