Synthesis, Structure Elucidation, and Redox Properties of [superscript 99]Tc Complexes of Lacunary Wells-Dawson Polyoxometalates: Insights into Molecular [superscript 99]Tc-Metal Oxide Interactions

Journal Article · Thu Nov 17 00:00:00 EST 2011 · Inorganic Chemistry

DOI:https://doi.org/10.1021/ic102111t· OSTI ID:1027662

McGregor, Donna; Burton-Pye, Benjamin P; Howell, Robertha C; Mbomekalle, Israel M; Bian, Fang; Mausolf, Edward; Poineau, Frederic; Czerwinski, Kenneth R; Francesconi, Lynn C ^[1]

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1. UNLV

The isotope {sup 99}Tc ({beta}{sub max}, 293.7; half-life, 2.1 x 10{sup 5} years) is an abundant product of uranium-235 fission in nuclear reactors and is present throughout the radioactive waste stored in underground tanks at the Hanford and Savannah River sites. Understanding and controlling the extensive redox chemistry of {sup 99}Tc is important in identifying tunable strategies to separate {sup 99}Tc from spent fuel and from waste tanks and, once separated, to identify and develop an appropriately stable waste form for {sup 99}Tc. Polyoxometalates (POMs), nanometer-sized models for metal oxide solid-state materials, are used in this study to provide a molecular level understanding of the speciation and redox chemistry of incorporated {sup 99}Tc. In this study, {sup 99}Tc complexes of the ({alpha}{sub 2}-P{sub 2}W{sub 17}O{sub 61}){sup 10-} and ({alpha}{sub 1}-P{sub 2}W{sub 17}O{sub 61}){sup 10-} isomers were prepared. Ethylene glycol was used as a 'transfer ligand' to minimize the formation of TcO{sub 2} {center_dot} xH{sub 2}O. The solution structures, formulations, and purity of TcVO({alpha}{sub 1}/{alpha}{sub 2}-P{sub 2}W{sub 17}O{sub 61}){sup 7-} were determined by multinuclear NMR. X-ray absorption spectroscopy of the complexes is in agreement with the formulation and structures determined from {sup 31}P and {sup 183}W NMR. Preliminary electrochemistry results are consistent with the EXAFS results, showing a facile reduction of the TcVO({alpha}{sub 1}-P{sub 2}W{sub 17}O{sub 61}){sup 7-} species compared to the TcVO({alpha}{sub 2}-P{sub 2}W{sub 17}O{sub 61}){sup 7-} analog. The {alpha}{sub 1} defect is unique in that a basic oxygen atom is positioned toward the {alpha}{sub 1} site, and the Tc{sup V}O center appears to form a dative metal-metal bond with a framework W site. These attributes may lead to the assistance of protonation events that facilitate reduction. Electrochemistry comparison shows that the ReV analogs are about 200 mV more difficult to reduce in accordance with periodic trends.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
• Sponsoring Organization: NIHDOE - BASIC ENERGY SCIENCES
• OSTI ID: 1027662
• Journal Information: Inorganic Chemistry, Vol. 50, Issue 5; ISSN 0020-1669
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
ABSORPTION SPECTROSCOPY
ATOMS
CHEMISTRY
DEFECTS
ELECTROCHEMISTRY
FISSION
GLYCOLS
ISOMERS
OXIDES
OXYGEN
RADIOACTIVE WASTES
REACTORS
SAVANNAH RIVER PLANT
SPENT FUELS
SYNTHESIS
TANKS
TECHNETIUM 99
UNDERGROUND STORAGE
URANIUM 235
WASTE FORMS
WASTES