Fast estimation of the internal conversion rate constant in photophysical applications

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Photochemistry

Background:

• Non-adiabatic coupling matrix elements (NACME) and internal conversion (k_IC) are crucial for understanding photophysical processes.
• Accurate calculation of these parameters often requires computationally intensive methods, limiting their application.
• Plotnikov's theory provides a theoretical framework, but its direct application can be complex.

Purpose of the Study:

• To develop an efficient and computationally tractable method for estimating NACME and k_IC.
• To enable accurate predictions of energy transfer efficiency and fluorescence quenching.
• To facilitate studies on vibronic effects in TADF emitters and solvent effects.

Main Methods:

• The proposed method relies on calculating electronic wave functions and excitation energies.
• It avoids computationally expensive calculations of electronic wave function derivatives with respect to nuclear coordinates.
• The method is based on Plotnikov's theory.

Main Results:

• NACME and k_IC were calculated for various molecules including porphyrins, azulene, naphthalene, pyrene, and fluorenone.
• Reverse k_IC and NACME were computed for the T₁→ T₂ transition in PTZ-DBTO2, a TADF emitter.
• Energy transfer efficiency was estimated for porphyrinoid dimers.

Conclusions:

• The developed method offers an efficient alternative for calculating NACME and k_IC.
• This approach simplifies the study of photophysical processes influenced by X-H vibrations, hydrogen bonding, and solvent effects.
• The method is applicable to a range of molecules and phenomena, including TADF emitters and energy transfer processes.