Self-modelling analysis applied to nanosecond transient absorption spectroscopy of flavone: an aid to elucidate and characterize reaction intermediates
Résumé
A nanosecond transient absorption spectroscopy study of flavone performed with a 248 nm pump radiation has been investigated with the support of a chemometric treatment: . The experimental spectra obtained in various solvent with a pump-probe delay lower than about 2 μs are in quite good concordance with those already presented in the literature. Nevertheless after about 10 μs, the spectrum pattern significantly evolves as a function of time particularly for the methanolic solution. A qualitative analysis together with a chemometric treatment of the experimental data allowed to elucidate and characterise two interdependent transient species in the alcoholic medium: the lowest T1 triplet state of flavone and the ketyl radical forming by H-abstraction reaction from the solvent. In cyclohexane and acetonitrile, the same species seem to be produced in the studied time-scale but the radical form is generated with variable quantum yield depending on the solvent polarity. The pure spectrum and the photochemical kinetics of each reaction intermediate could have been determined with the help of the second derivative calculation procedure.