A Competition among Three Ultrafast Photoinduced Events in Thiotropolone: Internal Conversion vs Intersystem Crossing vs ESIPT.

Gas phase excited-state quantum wavepacket dynamics simulations of the thiotropolone demonstrate the ultrafast triplet formation upon photoexcitation to the dipole-allowed S state. The dominant relaxation pathway of the S-T intersystem crossing, facilitated by the strong spin-orbit coupling and narrow energy gap, competes with the S to S/S internal conversion. The wavepacket populated in T via the former pathway decays to lower triplet states.

Rapid Intersystem Crossing Induced by Ultrafast Excited-State Intramolecular Proton Transfer in 3-Mercaptopyran-4-one.

Investigation into the photoinduced processes of 3-mercaptopyran-4-one is carried out using trajectory-based surface hopping simulations. Excitation into the near-degenerate higher singlet excited states reveals rapid internal conversion (IC) into S on a sub-50 fs timescale. Excited-state intramolecular proton transfer (ESIPT) also takes place simultaneously with IC.

Theoretical approach to modeling the early nonadiabatic events of ESIPT originating from three-state conical intersection in quinophthalone.

We explore the excited-state intramolecular proton transfer process of quinophthalone theoretically. This molecule possesses three low-lying singlet excited states ([Formula: see text] and [Formula: see text]) in a narrow energy gap of less than the N-H stretching frequency. Dynamics simulations show nonadiabatic wavepacket transfer to [Formula: see text] and [Formula: see text] upon initiating the wavepacket on [Formula: see text].