Bis(benzimidazole)-based ligands-directed the various dimensionality of metal–organic complexes based on carboxylates co-ligands: Syntheses, structures and properties

Four new metal–organic complexes [Co2(bbix)4(2,6-pdc)2]·4H2O (1), [Co(bbbm)1.5(2,6-pdc)]·2H2O (2), [Ni(bbmmb)2(dnba)2(H2O)2] (3) and [Ni(bbbm)1.5(dnba)2(H2O)]·(0.5bbbm)(H2O) (4) (bbix = 1,4-bis(benzimidazol-1-ylmethyl)benzene, bbbm = 1,1′-(1,4-butanediyl)bis-1H-benzimidazole, bbmmb = 4,4′-bis(benzimidazol-1-ylmethyl)biphenyl, 2,6-H2pdc = 2,6-pyridinedicarboxylic acid and Hdnba = 3,5-dinitrobenzoic acid) constructed from bis(benzimidazole)-based ligands with different flexibility and organic carboxylates co-ligands have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction analysis. Complex 1 possesses a binuclear Co2(bbix)2 ring. The adjacent binuclear units are packed into a one-dimensional (1D) supramolecular chain through very weak π–π stacking interactions. Complex 2 shows a two-dimensional (2D) 3-connected (63) topology connected by the flexible bbbm ligands. Complex 3 features a discrete mononuclear structure. The adjacent mononuclear units are linked by the H-bond interactions to form a 1D supramolecular chain. Complex 4 exhibits a 1D infinite chain formed by the Ni2(bbbm)2 rectangular macrocycles and bbbm ligands. The results clearly reveal that the flexibility of bis(benzimidazole)-based ligands have a great influence on the dimensionality and final structures of 1–4. The electrochemical and fluorescence properties for 1–4 have been investigated.