Ultrafast excited-state dynamics of aminoperylene and of its protonated form observed by femtosecond absorption spectroscopy

The photophysics of aminoperylene (APe) in various solvents, including a room-temperature ionic liquid, has been investigated by steady-state and femtosecond transient absorption spectroscopies. The ultrafast excited-state dynamics originates from the solvation of the polar S₁ state and not from a transition from a locally-excited to a charge-transfer state, as found with perylene-dimethylaniline. Addition of acid yields the protonated form APeH⁺, which exhibits similar photophysical properties than perylene, due to the suppression of the charge-transfer character of the S₀-S₁ transition. However, excited-state proton transfer, resulting to the formation of APe in the S₁ state, is observed in methanol.