Energy-Degeneracy-Driven Covalency in Actinide Bonding

• Published in: Journal of the American Chemical Society 2018-12, Vol.140 (51), p.17977-17984
• Main Authors: Su, Jing, Batista, Enrique R, Boland, Kevin S, Bone, Sharon E, Bradley, Joseph A, Cary, Samantha K, Clark, David L, Conradson, Steven D, Ditter, Alex S, Kaltsoyannis, Nikolas, Keith, Jason M, Kerridge, Andrew, Kozimor, Stosh A, Löble, Matthias W, Martin, Richard L, Minasian, Stefan G, Mocko, Veronika, La Pierre, Henry S, Seidler, Gerald T, Shuh, David K, Wilkerson, Marianne P, Wolfsberg, Laura E, Yang, Ping
• Format: Article
• Language: English
• Subjects: Actinium, plutonium, neptunium, uranium, thorium, Cl K-edge XAS, TDDFT, XANES; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.8b09436

Evaluating the nature of chemical bonding for actinide elements represents one of the most important and long-standing problems in actinide science. We directly address this challenge and contribute a Cl K-edge X-ray absorption spectroscopy and relativistic density functional theory study that quantitatively evaluates An–Cl covalency in AnCl6 2– (AnIV = Th, U, Np, Pu). The results showed significant mixing between Cl 3p- and AnIV 5f- and 6d-orbitals (t1u*/t2u* and t2g */eg *), with the 6d-orbitals showing more pronounced covalent bonding than the 5f-orbitals. Moving from Th to U, Np, and Pu markedly changed the amount of M–Cl orbital mixing, such that AnIV 6d- and Cl 3p-mixing decreased and metal 5f- and Cl 3p-orbital mixing increased across this series.