Syntheses, crystal structures and properties of four metal coordination complexes constructed from aromatic carboxylate and benzimidazole-based ligands

Four metal–organic coordination complexes, namely {[Zn(SIP)(mbi)2]·(Hmbi)·(H2O)2}n (1), {[Cd3(SIP)2(bbhb)3(H2O)4]·(H2O)2}n (2), [Co3(SIP)2(bbhb)4(H2O)2]n (3) and [Zn2(NIPA)2(mbi)2(H2O)3] (4) (H3SIP = 5-sulfoisophthalic acid, mbi = 2-methylbenzimidazole, bbhb = 1,1′-(1,4-butanediyl)bis-1H-benzimidazole and H2NIPA = 5-nitroisophthalic acid), have been hydrothermally synthesized. Single-crystal X-ray analyses show that these complexes have different structural features. In complex 1, the SIP3− anions bridge Zn(II) atoms to form 1D right-handed helical chains, which are further interconnected by hydrogen-bond interactions, forming a 3D supramolecular architecture. In complex 2, the Cd1 and Cd2 atoms are bridged by SIP3− ligands to form 1D chains, which are extended to 2D layer with Cd3 atoms as hinges. The 2D layers are further connected by bbhb ligands to give a 3D framework. The Co(II) atoms in compound 3 are bridged by SIP3− anions to generate 1D ladder-like chain; then, the 1D chains extend to 2D network by the connection of “L”-shaped bbhb ligands. Finally, the 2D networks are bridged by “S”-shaped bbhb ligands to give rise to the formation of 3D framework. In compound 4, the binuclear molecules are connected through hydrogen bonds to generate a 2D layer. The results illustrate that the carboxylate ligands and the versatile conformations of the bbhb ligands contribute to the structural diversity of these complexes. The photoluminescent properties of complexes 1, 2 and 4 are also studied.