Woodruff School of Mechanical Engineering

NRE 8011/8012 and MP 6011/6012 Seminar

Nuclear & Radiological Engineering and Medical Physics Programs

Title:

Applications of Actinide Covalency

Speaker:

Dr. Henry La Pierre

Affiliation:

Georgia Institute of Technology

When:

Thursday, October 20, 2016 at 11:00:00 AM

Where:

Boggs Building, Room 3-47

Host:

Dr. Nolan Hertel
nolan.hertel@me.gatech.edu
404-894-3601

Abstract

The role of 5f and 6d orbitals in actinide covalent bonding is the fundamental question in actinide chemistry. Actinide covalency is the key to designing efficient solution actinide extractants, to modeling and controlling actinide environmental transport, and to understanding magnetism and conductivity of actinide extended solid materials. In this talk, I will present synthetic and synchrotron spectroscopic approaches that measure and employ actinide covalent bonding.

I. Ligand K-edge XAS provides a quantifiable measure of 5f and 6d orbital contributions to covalent bonding across the actinides. Our recent ligand (O and Cl) K-edge X-ray absorption results on high symmetry, high and mid-valent trans-uranic complexes (Th, U, Np, and Pu) demonstrate the increasing 5f contributions across the series. This XAS analysis maps the covalent orbital contributions to the inverse trans-influence (ITI) necessary for understanding the reactivity of the dominant high-valent environmental species of U, Np, and Pu.

II. My research program has developed rational design principles for the stabilization of reactive high- and low-valent uranium complexes based on stabilizing covalent interactions. These studies have enabled the isolation and complete spectroscopic characterization of a molecular, divalent uranium complex – a new oxidation state for uranium. Additionally, the charge contributions to the ITI are established through the synthesis of isoelectronic high-valent uranium oxo and imide complexes.


Biography

Henry, also known by his nickname, Pete, is an Assistant Professor in the Department of Chemistry and Biochemistry at the Georgia Institute of Technology. Previously, he held the Director’s Postdoctoral Fellowship at Los Alamos National Laboratory. His studies there, with Dr. Stosh Kozimor and Dr. David Clark, included ligand K-edge XAS studies of transuranic complexes and the synthesis of f-element frustrated magnetic materials. He completed his undergraduate degree in Chemistry at Harvard University. In his undergraduate research, he worked in the laboratories of Prof. Jared Shaw (now at UC-Davis) at the Broad Institute on the synthesis on antibiotics. In summer research, he joined Prof. Masahiro Murakami’s group at Kyoto University to study the bridge between main group organometallics and organic methodology. His graduate work with Professors John Arnold, Robert Bergman, and Dean Toste at UC-Berkeley focused on the activation of dihydrogen by vanadium bisimido complexes. Following graduation, he studied ligand control of reactive low- and high-valent uranium complexes as a postdoctoral scholar with Prof. Karsten Meyer at FAU Erlangen-Nuremberg.

His independent research program develops the molecular and solid-state coordination chemistry of the f-elements for unique and scalable solutions to contemporary problems in energy use. These studies encompass applications in energy conversion (photochemical, magnetic) and transport (electrical) and in information storage and processing technology. These applications are supported by the development of methodologies for f-element separations and recycling.