Raman Spectral Characteristics of Bis(terdentate)cobalt(III) Complexes with N and O Donor Atoms

Abstract The Raman spectra were measured for the bis and mixed type cobalt(III) complexes with ethylenediamine-N-acetate (edma) in an aqueous solution in the skeletal vibration region. The Raman bands could be classified into five vibration modes; a totally symmetric stretching vibration mode in the 510–650 cm−1 region, a stretching vibration mode excluding the totally symmetric one in the 410–540 cm−1 region, a skeletal breathing vibration mode in the 370–490 cm−1 region, a skeletal bending deformation mode in the 270–420 cm−1 region, and a chelate ring deformation mode in the 220–270 cm−1 region. Differences in the skeletal vibrations were observed between the fac and mer isomers for the chelate ring arrangement. Further, differences for the chelate ring arrangement between the Raman spectra of sym-fac and unsym-fac isomers were observed in the skeletal bending deformation mode. The cobalt(III) complexes with the terdentate ligands containing N-methyl group exhibited Raman bands shifted to a lower frequency than those of the corresponding cobalt(III) complexes containing no N-methyl group in the totally symmetric stretching vibration mode region.