Photophysics of diiodine-substituted fluorinated boron–dipyrromethene: A time resolved study

In this letter nanosecond laser flash photolysis and femtosecond pump-probe spectroscopy are applied to clarify the nature, spectral and kinetic properties of transient species formed upon the excitation of 4,4-difluoro-2,6-diiodo-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene in ethanol solution. Picosecond dynamics observed after the excitation of this compound can be adequately interpreted as the following sequence of processes: ultrafast (0.6 ps) internal S2 − S1 conversion, vibrational relaxation of the hot S1 state (7 ps) and intersystem crossing (115 ps) to the long-lived T1 state (φТ = 0.56). The latter species decays in a microsecond timescale via oxygen quenching and T–T annihilation leading to the recovery of the ground state.