Metal–organic coordination polymers based on imidazolyl- and benzimidazolyl-containing 4,4′-bipy type ligands

• Two new semirigid imidazolyl containing 4,4′-bipy ligands were synthesized.
• Six new coordination compounds with bidentate or tridentate ligands.
• The ligands exhibit conformational diversity and variable coordination modes.
• A 2-D network and a 3-D motif with different {M(1,3-bdc2−)}n chains.
• Intense fluorescent emissions upon ultraviolet excitation.

Two new semirigid ligands 2,2′-bis(imidazol-1-ylmethyl)-4,4′-bis(4-pyridyl)biphenyl(L1) and 2,2′-bis(benzimidazol-1-ylmethyl)-4,4′-bis(4-pyridyl)biphenyl(L2) were designed and synthesized. Six new coordination compounds, {Cd(L1)Br2}n (1), {Cd(L1)(1,2-bdc)(H2O)⋅H2O}n (2), {Zn(L1) (1,3-bdc)⋅2.7H2O}n (3), {Co(L1)(1,3-bdc)⋅H2O}n (4), (1,2-bdc = 1,2-benzenedicarboxylate, 1,3-bdc = 1,3-benzenedicarboxylate, {Cd(L2)2(NO3)2⋅2H2O}n (5) and, [Ni(L2)2(H2O)2](ClO4)2⋅3H2O (6) based on them were obtained and characterized by single-crystal X-ray diffraction methods. 1 is a 2D infinite spongy cushion-like network. In 2, two bridging 1,2-bdc anions chelate two neighboring Cd(II) atoms with their carboxylate groups to form a 1D double chain. 3 displays a 2D network in which the wavelike {Zn(1,3-bdc2−)}n chains are linked to each other by bidentate L1. 4 adopts a unique 3D framework, in which the coplanar {Co(1,3-bdc2−)}n chains are connected to each other through tridentate L1. 5 features a 1D double chain motif composed of a square bimetallic ring as the building block. 6 is mononuclear nickel complex. The photoluminescence properties of L1–L2, 1–3 and 5 were investigated, and all of them exhibit intense fluorescent emissions in the solid state at room temperature.