Characterizing Anharmonic Vibrational Modes of Quinones with Two-Dimensional Infrared Spectroscopy

Two-dimensional infrared (2D IR) spectroscopy was used to study the vibrational modes of three quinonesbenzoquinone, naphthoquinone, and anthraquinone. The vibrations of interest were in the spectral range of 1560–1710 cm^–1, corresponding to the in-plane carbonyl and ring stretching vibrations. Coupling between the vibrational modes is indicated by the cross peaks in the 2D IR spectra. The diagonal and off-diagonal anharmonicities range from 4.6 to 17.4 cm^–1 for the quinone series. In addition, there is significant vibrational coupling between the in-plane carbonyl and ring stretching vibrations. The diagonal anharmonicity, off-diagonal anharmonicity, and vibrational coupling constants are reported for benzoquinone, naphthoquinone, and anthraquinone