Three cobalt(II) coordination polymers based on V-shaped aromatic polycarboxylates and rigid bis(imidazole) ligand: syntheses, crystal structures, physical properties and theoretical studies

To investigate the effect of organic anions on the coordination frameworks, we synthesized three new complexes, namely, Co(SDBA)(BIMB) (1), Co-2(SA)(BIMB)(1.5)(H2O) (2) and Co(FBA)(BIMB)(0.5)center dot H2O (3) (H(2)SDBA = 4,4'-dicarboxybiphenylsulfone, H(4)SA = 3,3',4,4'-diphenylsulfonetetracarboxylate acid and H(2)FBA = 4,4'-(hexafluoroisopropylidene)bis(benzoic acid)), which were obtained by the reactions of 4,4'-bis(1-imidazolyl)biphenyl (BIMB), and three V-shaped aromatic polycarboxylates as organic anions with Co(NO3)(2)center dot 6H(2)O. Single crystal structure analysis shows that complex 1 features a 3-fold interpenetrating three-dimensional (3D) framework with CdSO4-type topology. Complex 2 has a previously unknown 3D trinodal (4,4,6)-connected framework with a Schlafli symbol of (4.6(4).8)(2)(4(3).6(3))(2)(4(4).6(10).8). Complex 3 exhibits a three-dimensional 2-fold interpenetrating pillared helical-layer open framework of alpha-Po topology based upon binuclear paddlewheel units. The results reveal that the carboxylic building blocks with different conformations play a significant role in promoting the diversity of the observed structural motifs. The magnetic properties of the three complexes as well as the SHG and ferroelectric properties for 1 have also been investigated. Finally, theoretical calculations were carried out on the conformation of the BIMB ligand in the three complexes.