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

Abstract

Laser flash photolysis was used to study formation and decay of triplet states of bifunctional probes of type chromophore (naphthalene, 1,8-naphthaleneimide, pyrene)-sterically hindered amine (HAS). For all types of probes, the formation of the triplet state with absorption in the range 400–500 nm occurred after 266 nm excitation. The same triplet was formed at 355 nm excitation for probes extending absorption to this region. Triplet states of all probes were quenched by oxygen with rate constant 1–5×10 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 observed for N-(1-oxo-2,2,6,6-tetramethyl-4-piperidinyl)-1,8-naphthaleneimide in methanol.