Two cobalt(II) complexes based on a flexible bis(5,6-dimethylbenzimidazole) and rigid organic dicarboxylate ligands

Two new bis(5,6-dimethybenzimidazole)-based CoII complexes, Co(pydca)(L)2·2H2O (1) and [Co(bdc)(L)]n (2) (L = 1,3-bis(5,6-dimethylbenzimidazol-1-yl)-2-propanol, H2pydca = pyridine-2,6-dicarboxylic acid, H2bdc = 1,4-benzenedicarboxylic acid) were synthesized and characterized by physicochemical, spectroscopic methods and single-crystal diffraction. The cobalt(II) centers display different environments with distorted square-pyramidal geometry in 1 and a perfect tetrahedral geometry in 2. Complex 1 is a mononuclear structure, which is further assembled into a 3D supramolecular network via strong hydrogen bonding as well as π–π interactions; while complex 2 possesses a 2D corrugated (4,4) network that is further formed into a (3,4,4)-connected network with (62.84)(63)2(64.82)2-3,4,4T25 topology due to classical hydrogen bonds. The fluorescence and catalytic performances of the two complexes for the degradation of methyl orange by sodium persulfate have been investigated.