Primary processes of photodecomposition of 2-(5′-nitro-2′-furanyl)ethenyl-4-{N-[4′-(N,N-diethylamino)-1′-methylbutyl] carbamoyl} quinoline: Effect of oxygen and compound concentration

The study of the kinetics of photodecomposition of 2-(5′-nitro-2′-furanyl)ethenyl-4-{N-[4′-(N,N-diethylamino)-1′-methylbutyl] carbamoyl} quinoline (Quinifuryl, Q) was studied using steady-state and time resolved absorption spectroscopy. We detected the formation of the Q triplet state, which is characterized by the absorption maximum at 550 nm, triplet state energy ET = 18,200 ± 500 cm−1 and a decay constant k0=1.8×104 s−1. This triplet state is quenched by Q molecules in its ground state with the constant kq1=2.6×108 M−1 s−1 and by molecular oxygen with the constant kq2=2.0×109 M−1 s−1. The initial rate of Q photodecomposition under continuous irradiation by visible light (Vi) increases when the Q concentration is increased. In air and oxygen saturated solutions Vi is linearly proportional to Q concentration and does not depend on the O2 concentration. Our kinetic model of the process supposed two ways of Q photodecomposition: the reaction between Q molecules in triplet and ground states and the photodecomposition directly from the Q singlet excited state.