A DFT characterization of the structures and UV/vis absorption spectra of mauveine dyes

The s-cis and s-trans conformers are energetically nearly degenerate. Of the two rings appended to the phenazine nucleus, the phenyl ring is rigidly kept perpendicular whereas the aminophenyl ring is twisted and can easily oscillate. The electronic transitions responsible for the brilliant colour of the mauveine dyes are related to a modification of the π-bonding pattern within the diaminophenazine moiety.