Dispersed fluorescence spectra of jet-cooled 7-azaindole-(H2O)n (n = 1–3): Does photoinduced excited-state proton transfer occur or not?

The dispersed fluorescence spectra have been measured for the 7AI–(H2O)n (n = 1–3) clusters in a supersonic free jet expansion by exciting various vibronic bands in the S1 state. There has been controversy about the occurrence of the excited-state proton transfer in the n = 2,3 clusters. The absence of visible fluorescence from the tautomer forms of 7AI–(H2O)n (n = 1–3) indicates that the full tautomerization due to photoinduced excited-state proton transfer does not occur during the lifetime of the S1 state of the normal form each cluster.