Ultrafast photochromic reactions of fulgide photoswitches

The dynamics of fulgide photoswitches has been investigated applying femto-second transient absorption spectroscopy. The switching performance of differently substituted fulgides is equally improved in polymer (PMMA) environment as compared to liquid solution (toluene). In the polymer a single pathway for the ring-closure reaction, i.e., without the intermediate observed in toluene, allows for sub-picosecond reaction times. The ring-opening (on-switching) reaction in the donor-acceptor substituted energy-transfer system occurs on ps time scale.