Understanding the photodynamics of 3-hydroxypyran-4-one using surface hopping simulations

Photoinduced relaxation mechanisms of 3-hydroxypyran-4-one (3HOX) are explored by performing surface hopping dynamics simulations. Multiple conical intersections promote an internal conversion from higher singlet states to S1 within 50 fs. On a similar timescale, the intramolecular proton transfer occurs via a barrierless channel on S2. The proton-transferred (keto) tautomer then decays to its ground electronic state through an energetically accessible S1/S0 conical intersection. Eventually, the keto tautomer returns to S0 of enol form by back proton transfer. As events of the proton transfer cycle happen in the ultrafast timescale, 3HOX is expected to be highly photostable. [Display omitted] •Competing photorelaxation channels.•Simultaneous internal conversion and ESIPT within 50 fs.•Ultrafast ground-state back proton transfer.•Highly photostable.