Issue 30, 2016

Internal conversion and intersystem crossing pathways in UV excited, isolated uracils and their implications in prebiotic chemistry

Abstract

The photodynamic properties of molecules determine their ability to survive in harsh radiation environments. As such, the photostability of heterocyclic aromatic compounds to electromagnetic radiation is expected to have been one of the selection pressures influencing the prebiotic chemistry on early Earth. In the present study, the gas-phase photodynamics of uracil, 5-methyluracil (thymine) and 2-thiouracil—three heterocyclic compounds thought to be present during this era—are assessed in the context of their recently proposed intersystem crossing pathways that compete with internal conversion to the ground state. Specifically, time-resolved photoelectron spectroscopy measurements evidence femtosecond to picosecond timescales for relaxation of the singlet 1ππ* and 1nπ* states as well as for intersystem crossing to the triplet manifold. Trapping in the excited triplet state and intersystem crossing back to the ground state are investigated as potential factors contributing to the susceptibility of these molecules to ultraviolet photodamage.

Graphical abstract: Internal conversion and intersystem crossing pathways in UV excited, isolated uracils and their implications in prebiotic chemistry

Supplementary files

Article information

Article type
Paper
Submitted
16 Mär 2016
Accepted
03 Mai 2016
First published
10 Mai 2016

Phys. Chem. Chem. Phys., 2016,18, 20168-20176

Internal conversion and intersystem crossing pathways in UV excited, isolated uracils and their implications in prebiotic chemistry

H. Yu, J. A. Sanchez-Rodriguez, M. Pollum, C. E. Crespo-Hernández, S. Mai, P. Marquetand, L. González and S. Ullrich, Phys. Chem. Chem. Phys., 2016, 18, 20168 DOI: 10.1039/C6CP01790H

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