Quantum chemistry study on internal conversion of diphenyldibenzofulvene in solid phase

Area of Science:

• Physical Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Nonradiative decay is crucial for understanding photophysical processes in organic molecules.
• Diphenyldibenzofulvene (DPDBF) exhibits interesting photophysical properties, but its solid-state decay mechanisms require detailed investigation.

Purpose of the Study:

• To investigate the nonradiative decay process of DPDBF in the solid phase.
• To calculate the nonradiative rate constant using quantum chemistry methods.
• To elucidate the role of vibronic coupling and molecular geometry in solid-state decay.

Main Methods:

• Development of a solid-phase model using the ONIOM method.
• Geometry optimization for ground and excited states using DFT and TD-DFT.
• Calculation of vibrational frequencies, normal coordinates, Huang-Rhys factors, and vibronic coupling constants.

Main Results:

• Identified 12 vibrational modes with large reorganization energies and similar vibronic coupling constants.
• Determined that high-frequency modes likely dominate the internal conversion rate due to significant nuclear factors.
• Observed suppressed geometrical changes in the solid phase due to stacking effects, leading to reduced Huang-Rhys values.

Conclusions:

• The internal conversion rate in solid-phase DPDBF is primarily governed by high-frequency vibrational modes.
• Solid-state stacking effects reduce molecular distortions, impacting photophysical properties.
• This study provides insights into the nonradiative decay mechanisms of organic molecules in condensed phases.