Study of the Stability of 1-Alkyl-3-methylimidazolium Hexafluoroantimonate(V) Based Ionic Liquids Using X-ray Photoelectron Spectroscopy

Longo Jr, Luiz S.; Smith, Emily F.; Licence, Peter

Abstract

A series of highly pure 1-alkyl-3-methylimidazolium hexafluoroantimonate (V) ionic liquids was firstly investigated by XPS. Reliable binding energy values for all elements within the samples were obtained by applying a C 1s fitting model previously employed for other imidazolium ionic liquids, based on setting the C 1s aliphatic component to 285.0 eV when alkyl chains are longer than 8 carbons. We also observed a straightforward X-ray-mediated photoreduction of Sb (V) to Sb (III) species, i.e. reduction of [SbF6]- anion to volatile SbF3. Thus, binding energies values observed at 542.5 eV and 533.1 eV were attributed to Sb 3d3/2 (V) and Sb 3d5/2 (V), respectively, whereas values at 541.0 eV and 531.7 eV were found for Sb 3d3/2 (III) and Sb 3d5/2 (III), respectively. The SbF3 being formed can be lost either by evaporation and/or redistribution to the bulk. Providing the sample is cooled to freezing temperatures, the SbF3 is prevented from escaping the ionic liquid and it accumulated on the surface of cooled [C4C1Im][SbF6] and [C8C1Im][SbF6]. Particularly in the case of prolonged X-ray exposure of a cooled [C4C1Im][SbF6], an unprecedented further reduction of Sb (III) to Sb (0) was noticed. This study provides fundamental knowledge on the XPS data for antimony compounds as well as providing a step towards the surface analysis of materials composed by antimony species, notably the hexafluoroantimonate (V) anion.

Citation

Longo Jr, L. S., Smith, E. F., & Licence, P. (2016). Study of the Stability of 1-Alkyl-3-methylimidazolium Hexafluoroantimonate(V) Based Ionic Liquids Using X-ray Photoelectron Spectroscopy. ACS Sustainable Chemistry and Engineering, 4(11), 5953-5962. https://doi.org/10.1021/acssuschemeng.6b00919

• Journal Article Type: Article
• Acceptance Date: Aug 9, 2016
• Online Publication Date: Aug 19, 2016
• Publication Date: Nov 7, 2016
• Deposit Date: Aug 22, 2016
• Publicly Available Date: Aug 22, 2016
• Journal: ACS Sustainable Chemistry & Engineering
• Electronic ISSN: 2168-0485
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 4
• Issue: 11
• Pages: 5953-5962
• DOI: https://doi.org/10.1021/acssuschemeng.6b00919
• Public URL: https://nottingham-repository.worktribe.com/output/806174
• Publisher URL: http://pubs.acs.org/doi/abs/10.1021/acssuschemeng.6b00919
• Additional Information: This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Sustainable Chemistry and Engineering, copyright © American Chemical Society after peer review and technical editing by the publisher.