Neptunyl Peroxide Chemistry: Synthesis and Spectroscopic Characterization of a Neptunyl Triperoxide Compound, Ca2[NpO2(O2)3]·9H2O

Sarah Hickam, Debmalya Ray, Jennifer E.S. Szymanowski, Ru Ye Li, Mateusz Dembowski, Philip Smith, Laura Gagliardi, Peter C. Burns

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Little is known about the crystal chemistry of neptunyl peroxide compounds compared to uranyl peroxide compounds, for which dozens of structures have been described. Uranyl peroxides are formed over a broad range of pH and solution conditions, but neptunyl peroxide chemistry is complicated by the ability of H2O2 to act as an oxidizing or reducing agent for Np, depending on the conditions present. The combination of Np(V) in 1 M HCl, H2O2, and CaCl2 under alkaline conditions leads to the immediate crystallization of a neptunyl triperoxide monomer, Ca2[NpO2(O2)3]·9H2O, which is the first Np(VI)-based peroxide compound to be characterized in the solid state and is isostructural to Ca2[UO2(O2)3]·9H2O. The crystal structure reveals bond distances of 1.842(7) Å that are the longest reported to date for nonbridging Np(VI)-Oyl bonds. Computational studies probe the oxidation state and bond distances of the monomer unit and differences in Raman spectra of the neptunyl and uranyl triperoxide compounds.

Original languageEnglish (US)
Pages (from-to)12264-12271
Number of pages8
JournalInorganic chemistry
Issue number18
StatePublished - Sep 16 2019

Bibliographical note

Funding Information:
This research was funded by the U.S. Department of Energy, National Nuclear Security Administration, under Award Number DE-NA0003763. The authors thank Dr. Sergey M. Aksenov for his help with the VDP analysis. We thank the Materials Characterization Facility for some of the instrumentation used in this work.

Publisher Copyright:
Copyright © 2019 American Chemical Society.


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