Intricate Spin-Vibronic Dynamics and Excited-State Intramolecular Thiol Proton Transfer in Dithiotropolone

Area of Science:

• Photochemistry
• Quantum Chemistry
• Molecular Dynamics

Background:

• Dithiotropolone exhibits complex photophysical behavior.
• Understanding intramolecular proton transfer and intersystem crossing is crucial for photochemistry.

Purpose of the Study:

• To computationally investigate the mechanisms of intramolecular thiol proton transfer and triplet formation in dithiotropolone.
• To elucidate the roles of singlet and triplet states in these processes.

Main Methods:

• Computational investigation using quantum chemical methods.
• Simulations of nuclear wavepacket dynamics.
• Analysis of internal conversion and intersystem crossing pathways.

Main Results:

• The S3 state initiates simultaneous internal conversion (S3 to S2/S1) and intersystem crossing (S3-T4).
• Ultrafast internal conversion is observed in the triplet manifold, mirroring singlet dynamics.
• Thiol proton transfer occurs via multiple singlet states due to low energy barriers.
• Triplet formation is possible outside the Franck-Condon region through S1-T4 and S3-T5/T6 crossings.

Conclusions:

• Dithiotropolone displays intricate photophysical pathways involving both singlet and triplet states.
• Both internal conversion and intersystem crossing are significant decay channels.
• Proton transfer and triplet formation can occur through various mechanisms, both within and beyond the Franck-Condon region.