The Onset of Electron-Induced Proton-Transfer in Hydrated Azabenzene Cluster Anions

Author

Yi Wang
Xinxing Zhang
Svetlana Lyapustina
Michael M. Nilles
Shoujun Xu
Jacob D. Graham
Kit H. Bowen
John T. Kelly
Gregory S. Tschumper, Missouri University of Science and TechnologyFollow
Nathan I. Hammer

Abstract

The prospect that protons from water may be transferred to N-heterocyclic molecules due to the presence of an excess electron is studied in hydrated azobenzene cluster anions using anion photoelectron spectroscopy and computational chemistry. In the case of s-triazine (C₃H₃N₃), which has a positive adiabatic electron affinity, proton transfer is not energetically favored nor observed experimentally. Heterocyclic rings with only 1 or 2 nitrogen atoms have negative electron affinities, but the addition of solvating water molecules can yield stable negative ions. In the case of the diazines (C₄H₄N₂: pyrazine, pyrimidine, and pyridazine) the addition of one water molecule is enough to stabilize the negative ion, with the majority of the excess electron density in a π∗ orbital of the heterocycle but not significantly extended over the hydrogen bonded water network. Pyridine (C₅H₅N), with the most negative electron affinity, requires three water molecules to stabilize its negative ion. Although our computations suggest proton transfer to be energetically viable in all five N-heterocyclic systems studied here when three or more water molecules are present, proton transfer is not observed experimentally in the triazine nor in the diazine series. In pyridine, however, proton transfer competes energetically with hydrogen bonding (solvation), when three water molecules are present, i.e., both motifs are observed. Pyridine clusters containing four or more water molecules almost exclusively exhibit proton transfer along with solvated [C_6-xH_6-x+1N_x·OH]^- ions.

Recommended Citation

Y. Wang and X. Zhang and S. Lyapustina and M. M. Nilles and S. Xu and J. D. Graham and K. H. Bowen and J. T. Kelly and G. S. Tschumper and N. I. Hammer, "The Onset of Electron-Induced Proton-Transfer in Hydrated Azabenzene Cluster Anions," Physical Chemistry Chemical Physics, vol. 18, no. 2, pp. 704 - 712, Royal Society of Chemistry, Jan 2016.

The definitive version is available at https://doi.org/10.1039/c5cp02746b

Department(s)

Chemistry

Comments

National Science Foundation, Grant CHE- 0955550

International Standard Serial Number (ISSN)

1463-9076

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2024 Royal Society of Chemistry, All rights reserved.

Publication Date

01 Jan 2016