Multiphoton-gated cycloreversion reaction of a photochromic 1,2-bis(thiazolyl) perfluorocyclopentene diarylethene derivative

Cycloreversion processes of a 1,2-bis(thiazolyl) perfluorocyclopentene photochromic diarylethene 1 with extremely low reaction yield under steady state irradiation in chloroform solution (1.3 × 10−3) was investigated by means of picosecond and femtosecond laser photolysis methods. The cycloreversion reaction was drastically enhanced by more than two orders of magnitude (ca. ×400) by a picosecond 532 nm laser excitation in comparison with a steady state irradiation. From time-resolved transient absorption measurements, double pulse experiments, and excitation intensity dependence of the transient absorbance and the reaction efficiency, this enhancement was attributed to a stepwise two-photon absorption process leading to high excited state.