Electron transfer from halide ions to UO sub 2 sup 2+ excited-state ions in aqueous solution: Formation and decay of dihalide radical anions

Journal Article · Wed Apr 18 04:00:00 EDT 1990 · Inorganic Chemistry; (USA)

DOI:https://doi.org/10.1021/ic00333a021· OSTI ID:6711122

Burrows, H D ^[1]

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1. Universidade de Coimbra (Portugal)

The decay of the excited uranyl ion in water in the presence of Cl{sup {minus}}, Br{sup {minus}}, I{sup {minus}}, and SCN{sup {minus}} is studied by laser flash kinetic spectrophotometry. The four anions all quench *UO{sub 2}{sup 2+} by a bimolecular process suggested to involve electron or charge transfer. Steady-state luminescence studies suggest that there is also some static contribution to the quenching. For Br{sup {minus}}, I{sup {minus}}, and SCN{sup {minus}}, radical anions, X{sub 2}{sup {sm bullet}{minus}}, are observed. However, kinetic studies indicate that these are not formed directly from *UO{sub 2}{sup 2+} but probably come by bimolecular reaction of an intermediate uranium(V)/radical pair with the corresponding halide ion. The extinction coefficient for the *UO{sub 2}{sup 2+} absorption is reported, and by use of this and transient absorbance data radical-anion yields are obtained and found to depend linearly upon the halide anion concentration. The variation of the yield in the series I{sup {minus}}, SCN{sup {minus}}, and Br{sup {minus}} is interpreted in terms of the effect of overall free energy change on back-electron-transfer in the uranium(V)/radical pair. With the chloride system no significant yield of radical anion was observed. The decay of X{sub 2}{sup {sm bullet}{minus}} was found to be unaffected by the presence of uranyl ion, supporting the previously suggested mechanism for radical-anion decay in these systems. 68 refs., 6 figs., 2 tabs.

• OSTI ID: 6711122
• Journal Information: Inorganic Chemistry; (USA), Journal Name: Inorganic Chemistry; (USA) Vol. 29:8; ISSN 0020-1669; ISSN INOCA
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400702* -- Radiochemistry & Nuclear Chemistry-- Properties of Radioactive Materials
ACTINIDE COMPOUNDS
ANIONS
CHARGED PARTICLES
DATA
ELECTRON TRANSFER
ENERGY LEVELS
EXCITED STATES
EXPERIMENTAL DATA
INFORMATION
IONS
LUMINESCENCE
NUMERICAL DATA
URANIUM COMPOUNDS
URANYL COMPOUNDS