Electron attachment dynamics following UV excitation of iodide-2-thiouracil complexes

Abstract

The dynamics of low energy electron attachment to the thio-substituted uracil analog 2-thiouracil are investigated using time-resolved photoelectron spectroscopy (TRPES) of iodide·2-thiouracil (I -·2TU­­) binary clusters. In these experiments, the anions are excited at pump energies of 4.16 and 4.73 eV, and the ensuing dynamics are probed by photodetachment at 1.59 and 3.18 eV. Upon excitation near the vertical detachment energy (4.16 eV), dipole bound (DB) and valence bound (VB) anion signals appear almost instantaneously, and the DB state of the 2TU anion undergoes ultrafast decay (~50 fs). At 4.73 eV, there is no evidence for a DB state, but features attributed to two VB states are seen. The transient negative ions formed by photoexcitation decay by autodetachment and I- fragmentation. The I- dissociation rates and their dependence on excitation energy agree reasonably well with the Rice-Ramsperger-Kassel-Marcus calculations. Notable differences with respect to TRPES of the related iodide-uracil anion are observed and discussed.

Probing Anion–Molecule Complexes of Atmospheric Relevance Using Anion Photoelectron Detachment Spectroscopy

“…In and of themselves, ion–molecule complexes (IMCs) have historically inspired active scientific exploration because of their importance in gas-phase reactions and photochemistry, − the properties and dynamics in aqueous electrolytic solutions, − and physical processes in planetary atmospheres. − Negatively charged complexes in particular have proven to be fertile ground for study using mass-selective photodetachment spectroscopies, with fundamental physical insights on the anions and their associated neutrals pouring from the laboratories engaged in these studies. − These species, like cationic IMCs, can accumulate numerous neutral molecules, forming noncovalently bound clusters, a topic explored in a recent review by Sanov …”

Extreme ultraviolet time-resolved photoelectron spectroscopy of adenine, adenosine and adenosine monophosphate in a liquid flat jet

“…how the excess energy is efficiently dissipated in a non-destructive manner before inducing bond cleavage that can lead to biological damage. [6][7][8][9][10][11] A better understanding of the processes at the molecular level is crucial not only for a bottom-up understanding of the biological effects of UV light, but for elucidating the reasons for the selection of nucleobases as the elements of building blocks that define the genetic code. 12,13 To this end, we have applied extreme ultraviolet time-resolved photoelectron spectroscopy (XUV-TRPES) to investigate the relaxation dynamics of aqueous adenine (Ade), its nucleoside adenosine (Ado), and nucleotide adenosine-5-monophosphate (AMP), the structures of which, including two tautomeric forms of Ade, are shown in Scheme 1.…”

Extreme Ultraviolet Time-Resolved Photoelectron Spectroscopy of Adenine, Adenosine and Adenosine Monophosphate in a Liquid Flat Jet

“…how the excess energy is efficiently dissipated in a non-destructive manner before inducing bond cleavage that can lead to biological damage. [6][7][8][9][10][11] A better understanding of the processes at the molecular level is crucial not only for a bottom-up understanding biological effects of the UV light, but for elucidating the reasons for the selection of nucleobases as the elements of building blocks that define the genetic code. 12,13 To this end, we have applied extreme ultraviolet time-resolved photoelectron spectroscopy (XUV-TRPES) to investigate the relaxation dynamics of aqueous adenine (Ade), its nucleoside adenosine The absorption spectra of Ade, Ado and AMP are nearly identical.…”