Theoretical study of the electronic spectra of oxidized and reduced states of lumiflavin and its derivative

Time‐dependent density functional theory has been applied to investigate the electronic absorption spectrum of oxidized and reduced lumiflavin and its derivative, 8‐NH 2 ‐lumiflavin. The calculations allow the authors to explain the origin of the difference in spectral features between oxidized and reduced states of lumiflavin. For the reduced lumiflavin, a reasonable assignment of the experimental spectrum has been made for the first time. Furthermore, the results obtained reveal that the NH 2 group plays a critical role in shaping the spectral features of 8‐NH 2 ‐lumiflavin, and offer a reasonable explanation for the spectral changes upon substituting the NH 2 group for the CH 3 group of lumiflavin. © 2007 Wiley Periodicals, Inc. J Comput Chem 28: 727–739, 2007