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Updated: Jun 16, 2025

Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization
Published on: August 6, 2018
Evidence for the O-H⋅⋅⋅O=C Resonance-Assisted Hydrogen Bond in Tropolones and Quantification of its σ- and
Andrei V Afonin1, Danuta Rusinska-Roszak2
1A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of Russian Academy of Sciences, 1 Favorsky St., Irkutsk, 664033, Russian Federation.
Abstract:
For a series of tropolones, the nature of the intramolecular O-H⋅⋅⋅O=C hydrogen bond closing the five-membered quasi-cycle was studied. Enhancement of conjugation in the hydrogen-bonded rotamer was revealed. Quantification of hydrogen bond energy in tropolones via the molecular tailoring approach yields values in the range from 15 to 20 kcal/mol suggesting that the intramolecular interaction in tropolones has nature of the resonance-assisted hydrogen bond. The total resonance-assisted hydrogen bond energy in the tropolones was divided into σ- and π-components. The magnitudes of total energy of resonance-assisted hydrogen bond in the substituted tropolones can be controlled by the electronic properties of the substituents at the tropone ring. In 3-, 4-, and 5-substituted tropolones, the resonance-assisted hydrogen bond energy is raised due to electron-donating substituents and lowered due to electron-withdrawing ones. The opposite trend is observed in 7-substituted tropolones. The size of the π-shares plays a crucial role in establishing the total energy of resonance-assisted hydrogen bond. The reason for the occurrence of a resonance-assisted hydrogen bond in the tropolones is the molecular backbone aromaticity, since, in accordance with the Hückel rule, 10 π-electrons are delocalized.
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