Femtosecond fluorescence up-conversion and transient absorption studies of the S2 state in the hydrogen-bonded benzopyranthione–water complex

We have studied for the first time the photophysics of the thioketone, 4H-1-benzopyrane-4-thione (BPT), in water and deuterated water, by using femtosecond fluorescence up-conversion and transient absorption spectroscopies. We propose that the S2-state deactivation occurs in the hydrogen-bonded BPT–water complex. The lifetime of the complex in the S2 state is found to be as short as 1.0 ± 0.1 ps in H2O, and 2.2 ± 0.1 ps in D2O.