Transient absorption spectra of bifunctional probes of a chromophore-sterically hindered amine type in solution; study of the triplet route to deactivation

Laser flash photolysis was used to study formation and decay of triplet sta tes of bifunctional probes of type chromophore (naphthalene, 1,8-naphthalen eimide, pyrene)-sterically hindered amine (HAS). For all types of probes, t he formation of the triplet state with absorption in the range 400-500 nm o ccurred after 266 nm excitation. The same triplet was formed at 355 nm exci tation for probes extending absorption to this region. Tripler states of al l probes were quenched by oxygen with rate constant 1-5 x 10(9) dm(3) mol(- 1) cm(-1). Intermolecular quenching of triplet states of the parent probes by N-oxyl (1-oxo-2,2,6,6-tetramethyl-4-hydroxypiperidine) was effective for naphthalene type probes and practically no effective for pyrene ones. The efficiency of intramolecular quenching in oxidised probes was determined by type of chromophore. The most effective intramolecular quenching was obser ved for N-(1-oxo-2,2,6,6-tetramethyl-4-piperidinyl)-1,8-naphthaleneimide in methanol, (C) 2001 Elsevier Science B.V. All rights reserved.