Redox Properties and Interchromophoric Electronic Interactions in Isoalloxazine−Anthraquinone Dyads

The electrochemistry of a family of recently synthesized isoalloxazine cyclophanes containing anthraquinones, variously substituted and linked by aliphatic chains of different lengths, has been studied. The redox behavior of such species was elucidated by complementing the voltammetric studies with DFT molecular modelling. In these cyclophanes (mimicking the active centers of enzymes), the distance between chromophores and their reciprocal orientations were found to significantly modify their redox properties. Inter-moiety π−π stacking plays an important role in the electrochemical behavior by modulating the orbital energies, which leads to an inversion of the localization of the first reduction, with the anthraquinone being reduced before the more electron-accepting flavine.