Direct evidence of uranium(V) intermediates by electron spin resonance in photo- and electrolytic reduction processes of uranyl complexes in organic solutions

Abstract

ESR and optical spectra of pentavalent uranium have been observed in both processes of photo- and electrolytic reduction of UO 2(dimethylsulphoxide) 5(ClO 4) 2, UO 2(NO 3) 2 · 5dimethylsulphoxide and UO 2(NO 3) 2 · 2triethylphosphate in each corresponding organic ligand solution. The optical spectra measured in both reductions of these complexes indicate the formation of uranium(V) ( λ max ; 770, 970 and 1400 nm). Uranyl perchlorate shows a nearly symmetric ESR signal with g 1 = 2.5 and the linewidth of 150 mT (type 1) in both photo- and electrolytic reduction processes. Nitrates show the type 1 signal in electrolytic reduction but an asymmetric signal with g 1 = 1.97 (type 2) in photoreduction. These results reflect the difference in the first coordination spheres of perchlorate and nitrate complexes.