Ab initio calculations and vibrational spectroscopy on the phenylendiamine isomers

Molecular orbital calculations at HF and MP2 levels have been performed using the 6-31G** basis set for full geometry optimization of the phenylenediamine isomers. Our results show that only a transoid conformer is found for o-phenylenediamine, whereas cis and trans conformers exist for m- and p-phenylenediamine. Vibrational normal modes have been also analyzed for the gas phase and in chloroform solution, and compared with experimental data we have obtained using FTIR spectroscopy.