Femtosecond dynamics of photocyclization of 1-[(4-{5-[4-chloromethyl-2,5-dimethyl-3-thienyl]-2-oxo-1,3-dioxol-4-yl}-2,5-dimethyl-3-thienyl)methyl]pyridinium chloride

The photochromic ring closure in diarylethylene was studied by femtosecond laser spectroscopy. The absorption spectrum of the initial excited state under pulse excitation at 305 nm was observed. The kinetic scheme of transitions from the initial excited state to the closed-ring isomer as the final product is proposed.