Syntheses, structures and photoluminescence of a series of coordination frameworks based on dicarboxylate anion and bis(imidazole) ligand

Abstract

Abstract In this article, ten new coordination frameworks, namely, [Ni(H2O)6]·(L3) (1), [Zn(L3)(H2O)3] (2), [Cd(L3)(H2O)3]·5.25H2O (3), [Ag(L1)(H2O)]·0.5(L3) (4), [Ni(L3)(L1)] (5), [Zn(L3)(L1)0.5]·H2O (6), [Cd(L3)(L1)0.5(H2O)] (7), [CoCl(L3)0.5(L1)0.5] (8), [ZnCl(L3)0.5(L2)0.5] (9), and [CoCl(L3)0.5(L2)0.5] (10), where L1 = 1,1′-(1,4)-butanediyl)bis(imidazole), L2 = 1,1′-(1,4-butanediyl)bis(2-ethylbenzimidazole) and H2L3 = 3,3′-(p-xylylenediamino)bis(benzoic acid), have been synthesized by varying the metal centers and nitrogen-containing secondary ligands. These structures have been determined by single-crystal X-ray diffraction analyses, elemental analyses and IR spectra. In 1, the L3 anion is not coordinated to the Ni(II) center as a free ligand. The Ni(II) ion is coordinated by water molecules to form the cationic [Ni(H2O)6]2+ complex. The hydrogen bonds between L3 anions and [Ni(H2O)6]2+ cations result in a three-dimensional (3D) supramolecular structure of 1. In compounds 2 and 3, the metal centers are linked by the organic L3 anions to generate 1D infinite chain structures, respectively. The hydrogen bonds between carboxylate oxygen atoms and water molecules lead the structures of 2 and 3 to form 3D supramolecular structures. In 4, the L3 anion is not coordinated to the Ag(I) center, while the L1 ligands bridge adjacent Ag(I) centers to give 1D Ag–L1 chains. The hydrogen bonds among neighboring L3 anions form infinite 2D honeycomb-like layers, in the middle of which there exist large windows. Then, 1D Ag–L1 chains thread in the large windows of the 2D layer network, giving a 3D polythreaded structure. Considering the hydrogen bonds between the water molecules and L3 anions, the structure is further linked into a 3D supramolecular structure. Compounds 5 and 7 were synthesized through their parent compounds 1 and 3, respectively, while 6 and 9 were obtained by their parent compound 2. In 5, the L3 anions and L1 ligands connect the Ni(II) atoms to give a 3D 3-fold interpenetrating dimondoid topology. Compound 6 exhibits a 3D three-fold interpenetrating α-Po network structure formed by L1 ligands connecting Zn–L3 sheets, while compound 7 shows a 2D (4,4) network topology with the L1 ligands connecting the Cd–L3 double chains. In compound 8, the L1 ligands linked Co–L3 chains into a 2D layer structure. Two mutual 2D layers interpenetrated in an inclined mode to generate a unique 3D architecture of 8. Compounds 9 and 10 display the same 2D layer structures with (4,4) network topologies. The effects of the N-containing ligands and the metal ions on the structures of the complexes 1–10 were discussed. In addition, the luminescent properties of compounds 2–4, 6, 7 and 9 were also investigated.