Gas-Phase Reactivity Studies of Pentavalent Uranyl
Recently our group, in a collaboration with the Lawrence Berkeley National Laboratory, showed that gas-phase addition of O2 to [UVO2(CH3CO2)2]− exothermically produces the superoxide complex [UVIO2(O2)(CH3CO2)2]−. We surmised that molecules with electron affinities (EA) higher than that of O2 (EA = 0.4 eV), such as NO2 (EA = 2.3 eV), should also oxidize uranium(V) complexes; it was found that NO2 associates with [UVO2(CH3CO2)2]− to yield [UVIO2(O2)(CH3CO2)2]−. Our studies continued with SO2 (EA = 1.1 eV): [UVIO2(O2)(CH3CO2)2]− was produced by ESI and allowed to react with O2 and SO2 in a QIT mass spectrometer leading to the uranium(VI) complexes [UVIO2(O2)(CH3CO2)2(O2)]− and [UVIO2(O2)(CH3CO2)2(SO2)]− demonstrating that neutral SO2 can be activated by uranyl(V) complexes and be reduced to SO2-. Intriguingly, the exchange reaction of SO2 by O2 was observed but the reverse reaction did not occur, indicating that O2- binds more strongly than SO2- to uranyl(VI).
Contact person: Joaquim Marçalo