Extensive TDDFT Benchmark Study of the Resonance Raman Spectra of Lumiflavin

An extensive computational TDDFT resonance Raman study of lumiflavin is presented including 42 DFT functionals, benchmarked against the experimental Evolution Associated Spectra (EAS) of the equilibrated S₁ and T₁ states of FMN published earlier. Initially, off-resonance spectra were computed, yielding adequate agreement, and fine-tuning was achieved with the inclusion of specific frequency scaling factors. Since the experimental EAS were obtained under resonance for the singlet and near-resonance for the triplet state, the subsequent inclusion of resonance effects in the calculations improved the correlation for most functionals. Their evaluation according to specific criteria narrowed down the choice to HCTH, OLYP, and TPSSh. Among the included criteria were the percent error of the 0-0 transitions, the quantification of the increase/decrease in correlation due to the addition of resonance enhancements, and the reproduction of the singlet-triplet peak shifts. Owing to the extensive data set, valuable insights were gained to assist similar studies.