On the application of nanosecond laser flash photolysis to the investigation of the photoreactivity of di and triarylamines

This review aims to provide the readership with an overview of the applications of the time-resolved spectroscopic techniques (often combined with steady-state measurements) in the elucidation of the mechanism of the photochemical behaviour of diaryl- and triarylamines. Such derivatives undergo cyclization to the carbazoles or ionization to the corresponding amine radical cations depending on both the nature of the starting substrates and the reaction conditions. In this context, time-resolved spectroscopy techniques allowed for the detection and the full characterization of all the excited states and the transients involved in these processes. The main characteristics of such species, including lifetime, time-resolved absorption spectra, quantum yield values and rate constants of formation and decay in both homogeneous and micro-heterogeneous environment (e.g. aqueous surfactant solutions) are thus summarized in the presented paper.

This review focuses on the application of laser flash photolysis as a key spectroscopic tool in the elucidation of the mechanism of the photoinduced [6π]-electrocyclization reaction of diaryl- and triarylamines. This time-resolved methodology led to detect and demonstrate that transients triplet state of the amine; the triplet and the ground state of the 4a,4b-dihydrocarbazole are formed in a consecutive adiabatic pathway.