Versatile frameworks constructed from divalent metals with 4,4′-methylenedibenzoic acid and imidazole derivative ligands: Syntheses, crystal structures and physical properties

Seven coordination polymers, namely, [Zn(DBA)(Hpyim)]n·nH2O (1), [Cd(DBA)(Hpyim)]n (2), [Zn(DBA)(bix)]n·2nH2O (3), [Co(DBA)(bix)]n (4), [Ni(DBA)(bix)]n (5), [Co(DBA)(mbix)]n (6), and [Ni(DBA)(mbix)(H2O)2]n·nH2O (7), where H2DBA=4,4′-methylenedibenzoic acid, Hpyim=2-(2-pyridyl)imidazole, bix=1,4-bis(imidazol-1-ylmethyl) benzene and mbix=1,3-bis(imidazol-1-yl-methyl) benzene, were synthesized. Complex 1 is a one-dimensional (1D) infinite chain. Complex 2 has a two-dimensional (2D) 4-connected (4,4) network based on dinuclear units. Complex 3 features a 2D sheet constructed from mononuclear center. Complexes 4 and 5 exhibit similar 2D layers, which are further linked into 3D supramolecular frameworks through π–π interactions. Complex 6 possesses a 3D 5-fold interpenetrating diamond framework, while complex 7 shows a 1D double-strand chain. The results indicate that the coordination modes of DBA, auxiliary ligands and metal ions play important roles in the formation of the final framework. Moreover, the luminescent properties of 1–3 and nonlinear optical and ferroelectric properties of 1 were also investigated.

Seven new complexes were obtained by the reactions of 4,4′-methylenedibenzoic acid and several ancillary ligands with metal nitrate. The structural differences indicate that the different coordination modes of DBA anion, auxiliary N-donor ligands and metal ions play important roles in the formation of the final framework structures. Moreover, their physical properties were also investigated.Figure optionsDownload as PowerPoint slideHighlights
► Seven complexes based on 4,4′-methylenedibenzoic acid were obtained.
► The complexes were structurally characterized by single-crystal X-ray diffraction.
► The systematic investigation of the effects of anion and auxiliary N-donor ligands on the ultimate frameworks.
► Complex 1 has modest powder SHG activity and ferroelectric properties.