Determination of infrared and raman spectroscopic properties of an ortho-hydroxyaryl Schiff base derivative molecule

In this study, conformational analysis of Schiff base derivatives was performed using DFT/B3LYP method and 6-311++G(d,p) basis set to determine the most stable conformers of molecules. In the most stable conformer structure, it was observed that the C-N=CH-C azomethine group was in the trans structure and there was an intramolecular O-H–N hydrogen bond between the hydrogen atom of the hydroxy group in the ortho position and the nitrogen atom in the azomethine. It was observed that the total energy difference of conformer structures I and II, in which the free OH group is in cis and trans structures, is 0.35 kJ/mol. Potential energy curves were calculated for the phenol ring and free hydroxy groups. IR and Raman frequencies were calculated for the lowest energy conformers using the DFTB3LYP/6-311++G(d,p) method. Solid-state FT-IR spectra were recorded and compared with scaled frequency values. Due to the low molecular symmetry, many normal vibration bands were observed as mixed modes. It was observed that the observed and calculated vibration frequencies were in good agreement.