Zinc 1s Valence-to-Core X-ray Emission Spectroscopy of Halozincate Complexes

Clarke, Coby J.; Hayama, Shusaku; Hawes, Alexander; Hallett, Jason P.; Chamberlain, Thomas W.; Lovelock, Kevin R.J.; Besley, Nicholas A.

Abstract

The Zn 1s valence-to-core (VtC) X-ray emission spectra of seven ionic liquids have been measured experimentally and simulated on the basis of time-dependent density-functional theory (TDDFT) calculations. Six of the ionic liquids were made by mixing [C8C1Im]X and Zn(II)X2 at three different ZnX2 mole fractions (0.33, 0.50, or 0.67) for X = Cl or Br, and a further ionic liquid was made by mixing [P6,6,6,14]Cl and a mole fraction of ZnCl2 of 0.33. Calculations were performed for the [ZnX4]2–, [Zn2X6]2–, and [Zn4X10]2– ions to capture the expected metal complex speciation. The VtC emission spectra showed three bands arising from single-electron processes that can be assigned to emission from ligand p-type orbitals, zinc d-orbitals, and ligand s-type orbitals. For all seven ionic liquids, the highest occupied molecular orbital arises from the ligand p orbitals, and the spectra for the different size metal complexes for the same X were found to be very similar, in terms of both relative peak intensities and peak energies. For both experiments and TDDFT calculations, there was an energy difference of 0.5 eV between the Cl-based and Br-based metal complexes for the ligand s and p orbitals, while the Zn 3d orbital energies were relatively unaffected by the identity of the ligand. The TDDFT calculations find that for the ions with symmetrically equivalent zinc atoms ([Zn2X6]2– and [Zn4X10]2–), the most appropriate core-ionized reference state has a core-hole that is localized on a single zinc atom. In this framework, the spectra for the larger ions can be viewed as a sum of spectra for the tetrahedral complex with a single zinc atom with small variations in the structure of the coordinating ligands. Because the spectra are relatively insensitive to small changes in the geometry of the ligands, this is consistent with the small variation in the spectra measured in the experiment.

Citation

Clarke, C. J., Hayama, S., Hawes, A., Hallett, J. P., Chamberlain, T. W., Lovelock, K. R., & Besley, N. A. (2019). Zinc 1s Valence-to-Core X-ray Emission Spectroscopy of Halozincate Complexes. Journal of Physical Chemistry A, 123(44), 9552-9559. https://doi.org/10.1021/acs.jpca.9b08037

• Journal Article Type: Article
• Acceptance Date: Oct 14, 2019
• Online Publication Date: Oct 14, 2019
• Publication Date: Nov 7, 2019
• Deposit Date: Oct 28, 2019
• Publicly Available Date: Oct 15, 2020
• Journal: Journal of Physical Chemistry A
• Print ISSN: 1089-5639
• Electronic ISSN: 1520-5215
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 123
• Issue: 44
• Pages: 9552-9559
• DOI: https://doi.org/10.1021/acs.jpca.9b08037
• Public URL: https://nottingham-repository.worktribe.com/output/2976698
• Publisher URL: https://pubs.acs.org/doi/10.1021/acs.jpca.9b08037
• Additional Information: This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in The Journal of Physical Chemistry A, copyright © American Chemical Society after peer review. To access the final edited and published work see https://pubs.acs.org/doi/10.1021/acs.jpca.9b08037