Femtosecond spectroscopic study on photochromic salicylideneaniline

Photochromic reactions of salicylideneaniline (SA) have been studied in solution using femtosecond transient absorption spectroscopy and picosecond fluorescence measurements. In the excited state, SA undergoes intramolecular enol–keto tautomerism and subsequent isomerization to give a colored photoproduct. Both the proton transfer and photochromic product formation were found to occur within few hundreds of femtosecond. The mechanism of these two ultrafast processes and their solvent dependence are discussed.