Excited‐state intramolecular proton transfer driven by conical intersection in hydroxychromones

Abstract

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*).

Modern Theoretical Approaches to Modeling the Excited-State Intramolecular Proton Transfer: An Overview

“…Moving to the MCTDHF applications to simulating the ESIPT process, interesting results on the photophysics of hydroxychromones have been reported by Perveaux et al [ 148 ] and Anand et al [ 149 ]. In the former case, the full-dimensional (48 DOFs) ML-MCTDH method was applied to analyze the interplay between the ESIPT reaction and the out-of-plane hydrogen torsion in 3-hydroxychromone, while the latter study comprised analogical simulations for the 3-hydroxychromone and 5-hydroxychromone systems, performed at the multimode MCTDH level with the inclusion of 25 DOFs.…”

Excited-state dynamics of 3-hydroxychromone in gas phase

“…The new reaction pathway is unreactive with respect to the ESIPT process, and thus a new explanation for the slower ESIPT process has been proposed. Vennapusa et al 30 further investigated the nonadiabatic dynamics of 3-HC using the multiconfiguration time-dependent Hartree (MCTDH) method. A similar deactivation mechanism scheme was proposed.…”

“…A number of experimental and theoretical studies have been undertaken to investigate the photochemical and photophysical properties of 3-HC and its derivatives. 11–37 Especially, 3-HC, as the basic unit of its derivatives, is a good model system to study the excited-state dynamics because it can provide elementary information without perturbation from substituents. Clevalier et al 17 found that the photoinduced excited-state dynamics of 3-HC are solvent dependent.…”

ESIPT in the pyrrol pyridine molecule: mechanism, timescale and yield revealed using dynamics simulations

“…Dynamics methods on the other hand allow the explicit simulation of the proton transfer reaction. Full quantum dynamics methods such as Multi-Configuration Time-Dependent Hartree (MCTDH) [39][40][41][42][43][44] and semi-classical approaches such as Ab Initio Multiple Spawning (AIMS) 45,46 and surface hopping (with decoherence correction) [47][48][49][50][51][52][53] have been applied to investigate ESIPT. The Nuclear Electronic Orbital (NEO) method, which allows the full quantum treatment of a restricted set of nuclei (usually hydrogen), is a promising alternative in that context.…”