Cobalt(II) complexes with small variations in the heterocycle ligand, crystal structure and DFT calculations

Abstract

Novel mononuclear cobalt(II) complexes, [Co(mbipy)(H2O)(η2-NO3)(η-NO3)] (1), [Co(dmbipy)(H2O)(η2-NO3)(η-NO3)] (2) and [Co(dmphen)(H2O)(η2-NO3)(η-NO3)] (3) were synthesized by the reactions of Co(NO3)2·6H2O with bipyridine and phenanthroline derivatives (mbipy = 6-methyl-2,2́-bypiridine; dmbipy = 6,6́-dimethyl-2,2́-bypiridine and dmphen = 2,9-dimethyl-1,10-phenanthroline). The complexes were identified by elemental analysis, IR, UV–Vis spectroscopy and X-ray crystallography. In the molecular structure of the three complexes, the coordination geometry around Co(II) is distorted octahedral in a [CoN2O4] system. The crystal structure was stabilized with a network of OH···O and (CH···O classical hydrogen bond interactions as well as π-π interactions between the pyridine rings in 2 and 3. Furthermore, the density functional theory (DFT) calculations have been performed. Good consistency was observed between the calculated results and the experimental structure, in gas phase and aqua phase. DFT approach was used to interpreter the optical characterization. The electronic properties of the complexes were also calculated and compared. The origin of the intermolecular OH···O hydrogen bond in 3D structure of the complexes was explored by MEP.