Spectroscopy and photophysics of flavin-related compounds: 3-ethyl-lumiflavin

Electronic structure and singlet-singlet and triplet-triplet absorption spectra of 3-ethyl-lumiflavin were calculated using time-dependent density functional theory (TD-DFT) methods. The measured lower-energy transitions are well reproduced in calculations, which are limited by the neglect of the solvent interactions. All the observable singlet-singlet and triplet-triplet transitions have π-π* character. Singlet oxygen production by the studied compound demonstrated that, similar to other lumiflavins, it is an efficient singlet oxygen sensitizer (ϕΔ = 0.55). Radiationless deactivation of the S1 state in solutions was shown to result in the T1 state formation.