Dynamics of cyclization, cycloreversion, and multiphoton-gated reaction of a photochromic diarylethene derivative in crystalline phase

Cyclization and cycloreversion reactions of a photochromic diarylethene derivative, bis(2-methyl-5-phenylthiophen-3-yl)perfluorocyclopentene, in crystalline phase were investigated by means of picosecond laser spectroscopy. Rapid cyclization within a few picoseconds, as comparable to that in solution phase, was confirmed for the colorization reaction in the crystalline phase. On the other hand, cycloreversion reaction took place with a time constant of 25 ps. In addition, nonlinear enhancement of the cycloreversion process was observed. The excitation intensity dependence of the reaction profiles and the correlation of the apparent reaction yield with the time interval of two pulses employed for the excitation clearly revealed that the successive two-photon absorption process via the S-1 state, leading to higher excited states, opened the efficient cycloreversion process. The dynamics and mechanisms of the multiphoton-gated reaction in the crystalline phase were discussed by comparing the present results with those in solution phase.