Laser flash photolysis study of two aromatic N-oxyimidosulfonate photoacidgenerators

In this paper we study the photophysical and photochemical behavior of two aromatic N-oxyimidosulfonate photoacid generators (PAGs), N-trifluoromethyl sulfonyloxy-phthalimide (PIT) and N-trifluoromethylsulfonyloxy-1,8-naphthal imide (NIT), by means of absorption and emission stationary techniques and nanosecond and picosecond laser flash photolysis. Triplet states have been detected for both compounds; lifetimes of 12 mu s and 43 mu s (acetonitrile solution) and 2 mu s and 28 mu s, (benzene solution), were measured for PI T and NIT, respectively. Photoacid generation quantum yields have also been measured (Phi = 0.28 in acetonitrile, Phi = 0.21 in benzene for PIT; Phi, = 0.17 in acetonitrile, Phi, = 0.09 in benzene for NIT), using Rhodamine B Base as an acid sensor and 2-methyl-4,6-bis(trichloromethyl)-1,3,5-triazine as a suitable actinometer with 308-nm laser excitation. Evidence that phot oacid generation occurs through an ionic mechanism from the singlet state w as obtained.