We study the transient photophysical properties of a diarylethene with a
carboxylic anchor group by a combination of steady-state and ultrafast
emission and absorption spectroscopy. After excitation of the closed-ring
form, fluorescence with a quantum yield of 10−5 is observed and separated into
different spectro-temporal components. The S1 state of the closed-ring form
shows a lifetime of 1.3 ps and decays mainly by internal conversion to the S0
state of this isomer. This vibrationally hot ground state cools on a time
scale of 10 ps
