Ultrafast laser spectroscopic study on photochromic cycloreversion dynamics in fulgide derivatives: one-photon and multiphoton-gated reactions

Abstract

Cycloreversion processes of three photochromic fulgide derivatives in toluene solution were investigated by means of picosecond and femtosecond laser photolysis methods. Femtosecond laser irradiation revealed that the cycloreversion processes upon visible one-photon excitation took place within a few ps in these three derivatives. On the other hand, drastic enhancements of the reaction yield were observed under picosecond laser exposure. Excitation intensity effect of the reaction yield and dynamic behaviors revealed that the successive two-photon absorption process leading to higher excited states opened the efficient cycloreversion channel in the three derivatives. The reaction yields in higher excited states were found to be quite large in these three systems, 0.35–0.55, while those in the S1 state were 0.048–0.21. The correlation of the reaction yield in the S1 state with that in Sn states suggest the character of the electronic states connected by the optical absorption plays an important role in the control of the cycloreversion reaction.