Intrinsically Competitive Photoinduced Polycyclization and Double-Bond Shift through a Boatlike Conical Intersection

Area of Science:

• Photochemistry
• Theoretical Chemistry
• Organic Chemistry

Background:

• Cycloocta-1,3,5,7-tetraene (COT) is a molecule known for its complex photochemical behavior.
• Understanding the deactivation pathways of excited states is crucial for controlling chemical reactions.

Purpose of the Study:

• To elucidate the mechanism of deactivation for photoexcited cycloocta-1,3,5,7-tetraene (COT*).
• To investigate the role of conical intersections in the photochemical transformation of COT.
• To explain the formation of semibullvalene (SBV) and other isomers.

Main Methods:

• Ab initio electronic structure calculations were employed to study the potential energy surface of COT*.
• The study focused on identifying and characterizing novel conical intersection structures.
• Computational methods were used to simulate reaction pathways and product distributions.

Main Results:

• A novel type of conical intersection was identified as the key feature in the deactivation of COT*.
• The deactivation process through this conical intersection intrinsically leads to the formation of semibullvalene (SBV).
• The formation of a double-bond-shifted isomer of COT was also found to be intrinsically linked to this deactivation pathway.

Conclusions:

• The study provides a mechanistic view of COT* deactivation, highlighting the critical role of a novel conical intersection.
• The proposed mechanism successfully explains the experimental observation of semibullvalene (SBV) formation in both gas-phase and solution-phase studies.
• This work deepens the understanding of photochemical reaction dynamics in polyenes and provides a theoretical basis for experimental findings.