Benzylperoxy radical cation: an exceptionally stable and bound species

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Chemical Physics

Background:

• Benzylperoxy radical is an unsaturated alkyl peroxy radical.
• Alkyl peroxy radicals typically undergo dissociative ionization.
• Understanding benzylperoxy radical energetics is crucial for predicting its reactivity.

Purpose of the Study:

• Investigate the energetics of ionization and dissociation of the benzylperoxy radical.
• Explain the elusiveness of the benzylperoxy radical in photoionization and ion-molecule reactions.
• Re-evaluate the valence bond perspective and electronic effects governing its stability.

Main Methods:

• Explicitly correlated coupled-cluster methods were employed for high-accuracy electronic structure calculations.
• Localized intrinsic bond orbital (IBO) methods were used to analyze the benzylperoxy radical cation.
• Theoretical calculations determined adiabatic ionization energy and cationic dissociation barrier.

Main Results:

• Calculated adiabatic ionization energy of 9.331 eV.
• Calculated cationic dissociation barrier of 0.155 eV.
• These values predict the benzylperoxy radical's elusiveness, contrasting with typical dissociative ionization of similar radicals.

Conclusions:

• The benzylperoxy radical's stability is an exception among unsaturated alkyl peroxy radicals.
• Electronic effects responsible for its elusiveness necessitate a revised valence bond perspective.
• Reintroduction of Linnett double-quartet theory is proposed to bridge theoretical and mechanistic understanding of triplet species.