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IR-dip and IR–UV hole-burning spectra of jet-cooled 4-aminobenzonitrile–(H2O)1. Observation of π-type and σ-type hydrogen-bonded conformers in the CN site

Chemical Physics
Publication Date
DOI: 10.1016/s0301-0104(02)00501-3


Abstract The IR-dip spectra and IR–UV hole-burning spectra of jet-cooled 4-aminobenzonitrile–water 1:1 complex have been measured to investigate the effects of the introduction of two substituents into the aromatic ring on the hydrogen-bonding interaction and stable structures of the complex. We have obtained a clear evidence for the observation of three structural isomers by comparing the experimental IR spectra with the theoretical ones. The water molecule is bonded to the NH 2 site in isomer I, where the amino group can act as a proton donor and the amino hydrogen is bonded to the oxygen atom of water. Water is bonded to the CN site in isomers II and III. The structure of isomer II is very similar to benzonitrile–(H 2O) 1, where the water hydrogen is bonded to the cyano nitrogen and the oxygen atom of water is bonded to the ortho hydrogen atom. The water hydrogen is linearly hydrogen-bonded to the cyano nitrogen in isomer III. The intermolecular hydrogen bond in isomer II is σ-type, whereas that in isomer III is π-type. The proton-donor conformer in the NH 2 site and the σ-type linear conformer in the CN site have not been observed in the aniline–(H 2O) 1 and benzonitrile–(H 2O) 1 complexes, respectively. The observation of three stable structures has been successfully explained by atomic charges on the constituent atoms obtained by natural population analysis.

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