Computational Investigation of Infrared Vibrational Frequency Shift Modes in Schiff Base-Transition Metal Complexes

The computational investigation of change in the infrared vibrational frequency of some Schiff base-transition metal complexes relative to that observed in the Schiff base ligand was performed using density functional theory (DFT) based on the hybrid functional of three parameters Becke-3-Lee-Yang-Parr (B3LYP) with 6-31G(d,p) basis set. All the calculations were carried out using the Gaussian 09 program package, and the data obtained from the frontier molecular orbitals of the optimized ligand and its complexes showed that the complexes were less stable and more reactive than the ligand. The infrared vibrational frequencies of the Schiff base functional group had lower stretching vibrations in the complexes than the ligand, with the appearance of new vibrational frequencies therein not observed in the spectrum of the ligand. These observations can be used to confirm bond formation between a Schiff base and a transition metal in chemical synthesis.