Four cobalt(ii) coordination polymers with diverse topologies derived from flexible bis(benzimidazole) and aromatic dicarboxylic acids: syntheses, crystal structures and catalytic properties

Abstract

Four mixed ligand coordination polymers based on the flexible bis(5,6-dimethybenzimidazole) and aromatic dicarboxylic acids, namely, [Co(L1)(bpdc)]_n (1), {[Co(L1)(npht)]·0.5H₂O}_n (2), [Co(L2)(bpdc)]_n (3), and [Co(L3)(bpdc)(H₂O)]_n (4) (L1 = 1,4-bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene, H₂bpdc = 4,4′-biphenyldicarboxylic acid, L2 = 1,3-bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene, H₂npht = 3-nitrophthalic acid, L3 = 1,1′-bis(5,6-dimethylbenzimidazole)methane) have been hydrothermally synthesized and structurally characterized. Polymer 1 features a 3D three-fold interpenetrating dia array with a 4-connected 6⁶ network, while 2 exhibits a 3D noninterpenetrated 3-connected framework with a 10³-ThSi₂ architecture. 3 and 4 have two-dimensional 3-connected (6³) and 4-connected (4⁴.6²) topologies, respectively. Complex 4 ultimately is extended into an unusual 3D (3,5)-connected seh-3,5-P21/c supramolecular network via O–H⋯O hydrogen bonding interactions. The fluorescence and catalytic properties of the complexes for the degradation of the Congo red azo dye in a Fenton-like process are reported.