On the photostationary state of the flavylium network of chemical reactions

Calculation of the quantum yields from the photostationary state, in the cases where the thermal back reaction competes efficiently with the photoproducts formation is described. The system can be mathematically treated as a single equilibrium involving two opposite reactions, one driven by light of constant intensity and the other due to the thermal back reaction. By analogy with excited state redox potential calculations, the photostationary state can be defined by a constant, which is function of the number of absorbed photons by the cis and trans forms, the respective reaction quantum yields, the light intensity, irradiated volume, as well the rates of the thermal forward and backward thermal reactions (in the absence of light). Application of this concept to the flavylium network of chemical reactions is presented. The model compound 4′,7-dihydroxyflavylium was used to test the model.