The excited-state intramolecular proton transfer process in 3-hydroxyflavone is investigated based on the computed structural parameters and energetics of stationary points of vibronically coupled S1-S2 potential energy surfaces. A conical intersection close to the Franck-Condon point on S1 is identified. The minimum energy of the conical intersection is found to be near-degenerate with the equilibrium minimum of S2. Quantum nuclear wavepacket simulations revealed a small population transfer from the “bright” S1 to “dark” S2 on a time scale shorter than the O—H stretching vibrational period. Such a nonadiabatic transition opens up the possibility of new photophysical and photochemical pathways, including the proton transfer via S2.

Conformational differences-controlled fluorescence response of carbazole and triphenylamine appended cyano-pyridine donor–acceptor derivatives towards organic acids (TFA/PTSA).

Excited state intramolecular proton transfer (ESIPT) process based organic fluorophores provided opportunity to develop large Stokes shifted multifunctional fluorescence systems for white light emitting, chemosensing and bioimaging applications. In this...

The OH out-of-plane bend vibration induces an extremely rapid S2 to S1 internal conversion in 3-hydroxypyran-4-one.

Nonradiative decay pathways associated with vibronically coupled S1(ππ*)–S2(nπ*) potential energy surfaces of 3‐ and 5‐hydroxychromones are investigated by employing the linear vibronic coupling approach. The presence of a conical intersection close to the Franck–Condon point is identified based on the critical examination of computed energetics and structural parameters of stationary points. We show that very minimal displacements of relevant atoms of intramolecular proton transfer geometry are adequate to drive the molecule toward the conical intersection nuclear configuration. The evolving wavepacket on S1(ππ*) bifurcates at the conical intersection: a part of the wavepacket moves to S2(nπ*) within a few femtoseconds while the other decays to S1 minimum. Our findings indicate the possibility of forming the proton transfer tautomer product via S2(nπ*), competing with the traditional pathway occurring on S1(ππ*).