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Ionization-induced π→ H site switching dynamics in phenol-Ar3
Shun-ichi Ishiuchi1, Mitsuhiko Miyazaki, Makoto Sakai
1Chemical Resources Laboratory, Tokyo Institute of Technology, Yokohama 226-8503, Japan.
Physical Chemistry Chemical Physics : PCCP
|December 8, 2010
Summary
Researchers studied phenol-Argon clusters using spectroscopy. They identified new isomers and observed that ionization triggers a rapid rearrangement of Argon atoms from the aromatic ring to the hydroxyl group, forming hydrogen-bonded structures.
Area of Science:
- Physical Chemistry
- Spectroscopy
- Chemical Physics
Background:
- Understanding intermolecular interactions in van der Waals clusters is crucial for molecular science.
- Phenol-Ar(n) clusters serve as a model system for studying solvation effects and isomerism.
- Previous studies have characterized stable isomers, but less stable configurations remain elusive.
Purpose of the Study:
- To identify and characterize new isomers of phenol-Ar(n) clusters using electronic and vibrational spectroscopy.
- To investigate the structural dynamics and isomerization pathways of phenol-Ar(n) clusters upon ionization.
- To elucidate the role of argon ligand positioning (π-bonded vs. hydrogen-bonded) in cluster stability and reactivity.
Main Methods:
- Resonance-enhanced two-photon ionization (REMPI) spectroscopy to probe electronic transitions and identify isomers.
- Infrared (IR) ion dip spectroscopy to record vibrational spectra of neutral and cationic clusters.
- Picosecond time-resolved IR spectroscopy to study the dynamics of ionization-induced isomerization.
Main Results:
- Established an additivity rule for S(1) origin shifts, enabling the identification of two new, less stable isomers ((2/0) and (2/1)).
- Observed distinct spectral signatures for π-bonded argon ligands in neutral phenol-Ar(n) and hydrogen-bonded isomers in cationic phenol-Ar(n)+.
- Demonstrated that ionization of phenol-Ar(n)+ (with n=3) triggers a rapid π→H isomerization (< 3 ps) with no observable back reaction due to fast energy redistribution.
Conclusions:
- Sequential complexation of argon atoms to phenol follows an additivity rule, aiding in isomer identification.
- Ionization of phenol-Ar(n) clusters induces a significant structural rearrangement, favoring hydrogen-bonded configurations.
- The π→H isomerization is a fast, irreversible process in phenol-Ar(n)+ driven by the electronic changes upon ionization.
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