Characterizing
Anharmonic Vibrational Modes of Quinones
with Two-Dimensional Infrared Spectroscopy
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Abstract
Two-dimensional
infrared (2D IR) spectroscopy was used to study
the vibrational modes of three quinonesbenzoquinone, naphthoquinone,
and anthraquinone. The vibrations of interest were in the spectral
range of 1560–1710 cm<sup>–1</sup>, 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<sup>–1</sup> 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