Electronic spectra of pure uranyl(V) complexes: characteristic absorption bands due to a U(V)O2+ core in visible and near-infrared regions |
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Authors: | Mizuoka Koichiro Tsushima Satoru Hasegawa Miki Hoshi Toshihiko Ikeda Yasuhisa |
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Institution: | Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, 2-12-1-N1-34 O-okayama, Meguro-ku, Tokyo 152-8550, Japan. |
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Abstract: | To clarify the electronic spectral properties of uranyl(V) complexes systematically, we measured absorption spectra of three types of pure uranyl(V) complexes: U(V)O2(dbm)2DMSO]-, U(V)O2(saloph)DMSO]-, and U(V)O2(CO3)3]5- (dbm = dibenzoylmethanate, saloph = N,N'-disalicylidene-o-phenylenediaminate, DMSO = dimethyl sulfoxide). As a result, it was found that these uranyl(V) complexes have characteristic absorption bands in the visible-near-infrared (NIR) region, i.e., at around 640, 740, 860, 1470, and 1890 nm (molar absorptivity, epsilon = 150-900 M(-1).cm(-1)) for U(V)O2(dbm)2DMSO]-, 650, 750, 900, 1400, and 1875 nm (epsilon = 100-300 M(-1).cm(-1)) for U(V)O2(saloph)DMSO]-, and 760, 990, 1140, 1600, and 1800 nm (epsilon = 0.2-3.6 M(-1).cm(-1)) for U(V)O2(CO3)3]5-. These characteristic absorption bands of the uranyl(V) complexes are attributable to the electronic transitions in the U(V)O2+ core because the spectral features are similar to each other despite the differences in the ligands coordinated to the equatorial plane of the U(V)O2+ moiety. On the other hand, the epsilon values of U(V)O2(CO3)3]5- are quite smaller than those of U(V)O2(dbm)2DMSO]- and U(V)O2(saloph)DMSO]-. Such differences can be explained by the different coordination geometries around the center uranium in these uranyl(V) complexes. Consequently, the absorption bands of the uranyl(V) complexes in visible-NIR region were assigned to f-f transitions in the 5f1 configuration. |
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