Synthesis, spectral characterization and DFT calculations of new Co(II) complexes derived from benzimidazoles

Document Type: Research Article


Department of Chemistry, Mashhad Branch, Islamic Azad University, Mashhad, Iran


The synthesis, characterization and quantum-chemical investigations of two new Co(II) complexes derived from fluorescent benzimidazoles have been reported. Two new fluorescent heterocyclic ligands were synthesized from reduction of imidazo[4',5':3,4]benzo[1,2-c]isoxazole derivatives, and characterized by elemental analyses, IR, mass, and NMR spectra. Coordination of the bidentate ligands with Co(II) cation produced orange complexes. The structures of the complexes have been established by spectral and analytical data as well as Job’s method. Photophysical properties of the new ligands and Co(II) complexes were characterized by UV-Vis and fluorescence spectroscopies. An efficient charge transfer from the p-orbital of ligand to the Co(II) d-orbital could be proposed as the main reason for the color of the new complexes.. To gain insight into geometry, spectral properties and energy difference between the HOMO and LUMO frontier orbitals of the ligands and Co(II) complexes, the DFT calculations at the B3LYP/6-311++G(d,p) level were employed. The DFT-calculated spectral properties were in good agreement with the experimental values, and confirmed suitability of the optimized geometries for cobalt complexes.


Main Subjects