Theoretical Insight into Proton-Coupled Energy Transfer in an Anthracene-Phenol-Pyridine Triad

Area of Science:

• Photochemistry
• Quantum Chemistry
• Spectroscopy

Background:

• Proton-coupled energy transfer (PCEnT) involves coupled electronic excitation energy and proton transfer.
• Conventional energy transfer theories typically require spectral overlap between donor emission and acceptor absorption.

Purpose of the Study:

• To apply and validate a nonadiabatic PCEnT theory to an anthracene-phenol-pyridine triad system.
• To elucidate the mechanism of PCEnT in the absence of significant spectral overlap.

Main Methods:

• Utilized first-principles calculations to determine input parameters for the nonadiabatic PCEnT theory.
• Analyzed contributions of electron-proton vibronic states to PCEnT rate and absorption spectra.

Main Results:

• The developed theory accurately reproduced the experimentally measured PCEnT rate constant.
• Demonstrated that PCEnT can occur without detectable spectral overlap, challenging conventional theories.
• Identified that proton transfer lowers the energy of the local electron-proton transfer (LEPT) state, enabling sufficient spectral overlap.

Conclusions:

• PCEnT in the studied triad proceeds via a novel mechanism facilitated by proton transfer, overcoming the lack of spectral overlap.
• The findings enhance the fundamental understanding of PCEnT mechanisms.
• Provides insights for designing new PCEnT systems with tailored properties.