Photo-ionization Initiated Differential Ultrafast Charge Migration: Impact of Molecular Symmetries and Tautomeric Forms

TL;DR

This study investigates how molecular symmetry and tautomeric forms influence ultrafast charge migration after photo-ionization, revealing distinct charge dynamics in different tautomers and orbital symmetries, with implications for molecular control and fragmentation.

Contribution

It provides the first ab initio analysis of charge migration in tautomers, highlighting the role of symmetry and tautomerism in ultrafast electron dynamics.

Findings

Keto and enol tautomers exhibit opposite charge migration directions.

A' orbitals show faster, more delocalized charge dynamics than a'' orbitals.

Molecular symmetry and tautomerism significantly affect charge migration pathways.

Abstract

Photo-ionization induced ultrafast electron dynamics is considered as a precursor to the slower nuclear dynamics associated with molecular dissociation. Here, using ab initio multielectron wave-packet propagation method, we study the overall many-electron dynamics, triggered by the ionization of outer-valence orbitals of different tautomers of a prototype molecule with more than one symmetry element. From the time evolution of the initially created averaged hole density of each system, we identify distinctly different charge dynamics response in the tautomers. We observe that keto form shows charge migration direction away from the nitrogen bonded with tautomeric hydrogen, while in enol - away from oxygen bonded to tautomeric hydrogen. Additionally, the dynamics following ionization of molecular orbitals of different symmetry reveal that a' orbitals show fast and highly delocalized charge in comparison to a" symmetry. These observations indicate why different tautomers respond differently to an XUV ionization, and might explain the subsequent different fragmentation pathways. An experimental schematics allowing detection and reconstruction of such charge dynamics is also proposed. Although the present study uses a simple, prototypical bio-relevant molecule, it reveals the explicit role of molecular symmetry and tautomerism in the ionization-triggered charge migration that controls many ultrafast physical, chemical, and biological processes, making tautomeric forms a promising tool of molecular design for desired charge migration.