Tuning the Cation–Anion Interactions by Methylation of the Pyridinium Cation: An X-ray Photoelectron Spectroscopy Study of Picolinium Ionic Liquids

Men, Shuang, Licence, Peter ORCID: https://orcid.org/0000-0003-2992-0153, Luo, Huimin and Dai, Sheng (2020) Tuning the Cation–Anion Interactions by Methylation of the Pyridinium Cation: An X-ray Photoelectron Spectroscopy Study of Picolinium Ionic Liquids. The Journal of Physical Chemistry B, 124 (30). pp. 6657-6663. ISSN 1520-6106

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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.

Item Type:	Article
Faculty \ School:	Faculty of Science > School of Chemistry, Pharmacy and Pharmacology
Related URLs:	https://www.scopus.com/pages/publication...
Depositing User:	LivePure Connector
Date Deposited:	05 Oct 2026 11:46
Last Modified:	05 Oct 2026 15:00
URI:	https://ueaeprints.uea.ac.uk/id/eprint/104723
DOI:	10.1021/acs.jpcb.0c05872

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