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X-ray absorption study of platinum and palladium atoms in argon matrices: Evidence for platinum in a substitutional site and a short Pd–Ar interaction

Harris, Neil; Sakr, Ahmed K.; Snelling, Howard V.; Young, Nigel A.

Authors

Neil Harris

Ahmed K. Sakr

Dr Nigel Young N.A.Young@hull.ac.uk
Senior Lecturer/ Director of Studies/ Deputy Head of Chemistry and Biochemistry/ Industrial Placements Coordinator



Abstract

The Pt L3-edge X-ray absorption spectrum of Pt atoms generated in a hollow cathode sputtering device and trapped in an Ar matrix yielded a PtAr distance of 3.78(4) Å with a coordination number of ca. 12 which confirms the evidence from electronic absorption spectroscopy that Pt atoms occupy a substitutional site in the Ar lattice. These data also yield a van der Waals radius for Pt atoms of 1.90 Å. The Pd K-edge X-ray absorption spectrum of sputtered Pd atoms trapped in an Ar matrix is radically different to that for Pt atoms. The analysis reveals a much shorter PdAr distance of 2.53(3) Å with a low coordination number close to 1, together with an “atomic” EXAFS like spectrum with no significant oscillations indicating the absence of any well defined nearest neighbours. On annealing to 25 K, the 2.53(3) Å interaction essentially disappears to leave the “atomic” spectrum. The featureless “atomic” spectrum is associated with Pd 1S0 atoms in an argon substitutional site, or other site such as a grain boundary with high disorder. The short PdAr distance of 2.53(3) Å is consistent with Pd atoms with a 1S0 atomic ground state in an interstitial octahedral site, the formation of a PdArn exciplex with a short PdAr distance, or the formation of a more formal palladium argon compound such as PdAr2. Although it is not possible to be definitive, the most likely carrier of the short PdAr distance is a PdArn exciplex. What is clear is that this work has identified a short PdAr interaction for the first time.

Journal Article Type Article
Publication Date Nov 15, 2018
Journal Journal of Molecular Structure
Print ISSN 0022-2860
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 1172
Pages 80-88
APA6 Citation Harris, N., Sakr, A. K., Snelling, H. V., & Young, N. A. (2018). X-ray absorption study of platinum and palladium atoms in argon matrices: Evidence for platinum in a substitutional site and a short Pd–Ar interaction. Journal of molecular structure, 1172, 80-88. https://doi.org/10.1016/j.molstruc.2018.06.024
DOI https://doi.org/10.1016/j.molstruc.2018.06.024
Keywords Matrix isolation; EXAFS; Electronic absorption spectroscopy; Platinum atoms; Palladium atoms; Palladium-argon bond
Publisher URL https://www.sciencedirect.com/science/article/pii/S0022286018307257?via%3Dihub
Copyright Statement © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

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Copyright Statement
© 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/





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