Following Flavin's Vibrational Modes to Probe Anharmonicities and Low-Lying Conical Intersections
Vy Vu1, Samer Gozem1
1Department of Chemistry, Georgia State University, Atlanta, Georgia 30303, United States.
The Journal of Physical Chemistry. B
|December 6, 2025
Summary
Anharmonicity in flavin vibrational modes, particularly Franck-Condon active ones, affects UV-Vis spectroscopy. These findings improve computational and experimental studies of flavins and their photophysical properties.
Area of Science:
- Computational Chemistry
- Spectroscopy
- Photochemistry
Background:
- Flavins are essential biological molecules studied via UV-Vis, FTIR, and Raman spectroscopy.
- Spectroscopic methods excite vibrational modes, influencing electronic transitions and absorption profiles.
- Accurate vibrational frequency prediction is crucial for interpreting experimental flavin spectra.
Purpose of the Study:
- To investigate the harmonicity of flavin vibrational modes using computational methods.
- To assess the impact of anharmonicity on UV-Vis absorption profiles and spectral interpretation.
- To identify potential photophysical deactivation pathways in flavins.
Main Methods:
- Time-dependent density functional theory (TD-DFT) was employed on lumiflavin.
- Ground and excited-state potential energy surfaces were mapped along vibrational modes.
- Potential energy surfaces were fitted to identify anharmonic vibrational modes.
Main Results:
- Several Franck-Condon active modes exhibited anharmonic behavior.
- Anharmonicity helps explain discrepancies between computed and experimental flavin absorption wavelengths.
- Low-lying conical intersections between excited states were identified as potential deactivation channels.
Conclusions:
- Anharmonicity significantly influences flavin spectroscopy, impacting UV-Vis profiles.
- Computational insights aid in refining experimental spectroscopic analyses of flavins.
- Conical intersections offer mechanistic insights into flavin photophysics in nonpolar environments.
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