Excited-State Charge Transfer Coupling from Quasiparticle Energy Density Functional Theory

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• The Quasiparticle Energy (QE) scheme, derived from Density Functional Theory (DFT), effectively models excitation energies, including those with charge transfer characteristics.
• Accurate calculation of electron transfer (ET) couplings is crucial for understanding photochemical and photophysical processes.

Purpose of the Study:

• To extend the Quasiparticle Energy (QE) scheme for calculating electron transfer (ET) couplings between two excited states.
• To evaluate the performance of the extended QE scheme using a model donor-acceptor complex.

Main Methods:

• Density Functional Theory (DFT) calculations were employed to develop the Quasiparticle Energy (QE) scheme.
• The extended QE scheme was applied to a furan and 1,1-dicyanoethylene (DCNE) donor-acceptor complex.
• Generalized Mülliken-Hush and fragment charge-difference schemes were used for coupling calculations.
• Comparisons were made with Time-Dependent DFT (TDDFT) results and couplings derived from half-energy gaps with an external field.

Main Results:

• The extended QE scheme successfully calculated electron transfer (ET) couplings involving both charge transfer and local excitation states.
• QE-derived couplings showed good agreement with TDDFT results.
• QE couplings demonstrated superior exponential distance dependence compared to TDDFT.
• The QE scheme significantly reduced computational time.

Conclusions:

• The Quasiparticle Energy (QE) scheme is a robust and computationally efficient method for calculating electron transfer (ET) couplings between excited states.
• The extended QE approach provides a reliable tool for investigating charge transfer phenomena in molecular systems.
• This method holds promise for accelerating research in areas requiring accurate ET coupling calculations.