Abstract
X-ray photoelectron spectroscopy is used to investigate the impact of methylation on the electronic environment of pyridinium cations. Because of the electron-donating effect of the methyl group, there is a significant increase in electron density on the cationic nitrogen. The shift of the N 1s binding energy is inversely proportional to the anion basicity. The methylation position on the electronic environment of the cationic nitrogen is investigated. The N 1s binding energy follows the trend: 1-octylpyridinium > 1-octyl-3-picolinium > 1-octyl-4-picolinium > 1-octyl-2-picolinium, which is in good agreement with the cation acidity. The increase in the inductive effect subsequently weakens the cation-anion interactions through charge transfer from the anion to the cation, causing a subtle change in the electronic environment of the anion. Such an effect is noticeably reflected in the Br 3d binding energy. It shows that the Br 3d5/2 binding energy of 1-octyl-2-picolinium bromide is 0.2 eV lower than that of 1-octylpyridinium bromide.
| Original language | English |
|---|---|
| Pages (from-to) | 6657-6663 |
| Number of pages | 7 |
| Journal | Journal of Physical Chemistry B |
| Volume | 124 |
| Issue number | 30 |
| DOIs | |
| State | Published - Jul 30 2020 |
Bibliographical note
Publisher Copyright:Copyright © 2020 American Chemical Society.
Funding
This manuscript was authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ). Acknowledgments S.M. thanks Liaoning Provincial Foundation of Science and Technology (20180550482) for the financial support. S.M. is also grateful to China Scholarship Council for the grant of a scholarship under State Scholarship Fund (201808210439) as a Visiting Scholar in Oak Ridge National Laboratory (ORNL). H.L. and S.D. are supported by U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. Dr. Chi-Linh Do-Thanh from The University of Tennessee (Knoxville) is acknowledged for NMR characterization. Drs. Jun Qu and Harry Meyer III from ORNL are acknowledged for XPS training and helpful discussions. XPS characterization was performed at ORNL’s Materials Characterisation Centre.
| Funders | Funder number |
|---|---|
| U.S. Department of Energy | |
| Office of Science | |
| Basic Energy Sciences | |
| Oak Ridge National Laboratory | |
| Chemical Sciences, Geosciences, and Biosciences Division | |
| China Scholarship Council | 201808210439 |
| University of Science and Technology Liaoning | 20180550482 |