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Zinc 1s valence-to-core X-ray emission spectroscopy of halozincate complexes

DOI: 10.1021/acs.jpca.9b08037 DOI Help

Authors: Coby J. Clarke (Imperial College London) , Shusaku Hayama (Diamond Light Source) , Alexander Hawes (University of Leeds) , Jason P. Hallett (Imperial College London) , Thomas W. Chamberlain (University of Leeds) , Kevin R. J. Lovelock (University of Reading) , Nicholas A. Besley (University of Nottingham)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: The Journal Of Physical Chemistry A

State: Published (Approved)
Published: October 2019
Diamond Proposal Number(s): 17787

Abstract: The Zn 1s valence-to-core (VtC) X-ray emission spectra of six ionic liquids have been measured experimentally and simulated based upon time-dependent density-functional theory (TDDFT) calculations. The seven 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-ionised reference state has a core-hole that is localised 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. Since 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 experiment.

Subject Areas: Chemistry

Instruments: I20-Scanning-X-ray spectroscopy (XAS/XES)

Added On: 21/10/2019 11:11

Discipline Tags:

Physical Chemistry Chemistry

Technical Tags:

Spectroscopy X-ray Emission Spectroscopy (XES)