Characterizing excited-state intramolecular proton transfer in 3-hydroxyflavone with ultrafast transient infrared spectroscopy

Vibrational dynamics associated with excited-state intramolecular proton transfer in 3-hydroxyflavone and 3-hydroxy-2-(thiophen-2-yl)chromen-4-one are characterized with ultrafast transient infrared spectroscopy. The spectroscopic data reveal rapid (<100 fs) proton transfer dynamics in both species, followed by vibrational relaxation of the tautomer products within a few picoseconds. Coherent coupling of the shared proton to low-frequency modes along the hydrogen bond coordinate are also observed in the ground electronic states.