Multiple ESIPT pathways originating from three-state conical intersections in tropolone

Area of Science:

• Theoretical Chemistry
• Quantum Dynamics
• Spectroscopy

Background:

• Tropolone exhibits complex electronic excited states (S1, S2, S3).
• Understanding internal conversion decay is crucial for its photochemistry.

Purpose of the Study:

• Investigate internal conversion decay dynamics in tropolone's excited states.
• Explore conical intersections and vibronic coupling effects.

Main Methods:

• Linear vibronic coupling approach.
• Diabatic vibronic Hamiltonian with 32 vibrational degrees of freedom.
• Simulation of photoinduced S0 → S1 and S0 → S2 transitions.

Main Results:

• Direct nonadiabatic population transfer from S1 to S3 observed, bypassing S2.
• Wavepacket on S2 passes through S2-S3 and S1-S3 conical intersections.
• Identified multiple proton transfer channels on coupled potential energy surfaces.

Conclusions:

• Internal conversion in tropolone is complex, involving multiple excited states and conical intersections.
• Proton tunneling dynamics require advanced treatment beyond simple double well potentials.