Determining the Intermolecular Structure in the S₀ and S₁ States of the Phenol Dimer by Rotationally Resolved Electronic Spectroscopy

Graphical Abstract

Excited state structures: The intermolecular geometry of the phenol dimer is determined from the rotationally resolved UV spectra of five isotopomers. The spectra are analyzed by a fitting strategy based on a genetic algorithm. The authors find that the electronic ground state has a longer hydrogen bond and a smaller tilt angle between the aromatic rings than the excited state (see picture).

Abstract

The rotationally resolved UV spectra of the electronic origins of five isotopomers of the phenol dimer have been measured. The complex spectra are analyzed using a fitting strategy based on a genetic algorithm. The intermolecular geometry parameters have been determined from the inertial parameters for both electronic states and compared to the results of ab initio calculations. In the electronic ground state, a larger hydrogen-bond length than in the ab initio calculations is found together with a smaller tilt angle of the aromatic rings, which shows a more pronounced dispersion interaction. In the electronically excited state, the hydrogen-bond length decreases, as has been found for other hydrogen-bonded clusters of phenol, and the two aromatic rings are tilted less toward each other.