Groenewold G S, Oomens J, de Jong W A, Gresham G L, McIlwain M E, Van Stipdonk M J
Idaho National Laboratory, Idaho Falls, ID, USA.
Phys Chem Chem Phys. 2008 Feb 28;10(8):1192-202. doi: 10.1039/b715337f. Epub 2007 Dec 21.
Wavelength-selective infrared multiple photon photo-dissociation (IRMPD) was used to generate spectra of anionic nitrate complexes of UO(2)(2+) and Eu(3+) in the mid-infrared region. Similar spectral patterns were observed for both species, including splitting of the antisymmetric O-N-O stretch into high and low frequency components with the magnitude of the splitting consistent with attachment of nitrate to a strong Lewis acid center. The frequencies measured for UO(2)(NO(3))(3) were within a few cm(-1) of those measured in the condensed phase, the best agreement yet achieved for a comparison of IRMPD with condensed phase absorption spectra. In addition, experimentally-determined values were in good general agreement with those predicted by DFT calculations, especially for the antisymmetric UO(2) stretch. The spectrum from the UO(2)(NO(3))(3) was compared with that of Eu(NO(3))(4), which showed that nitrate was bound more strongly to the Eu(3+) metal center, consistent with its higher charge. The spectrum of a unique uranyl-oxo species having an elemental composition UO(9)N(2) was also acquired, that contained nitrate absorptions suggestive of a UO(2)(NO(3))(2)(O) structure; the spectrum lacked bands indicative of nitrite and superoxide that would be indicative of an alternative UO(2)(NO(3))(NO(2))(O(2)) structure.
波长选择性红外多光子光解离（IRMPD）被用于在中红外区域生成UO(2)(2+)和Eu(3+)的硝酸根阴离子配合物的光谱。两种物种都观察到了相似的光谱模式，包括反对称O-N-O伸缩振动分裂为高频和低频成分，分裂幅度与硝酸根附着在强路易斯酸中心一致。UO(2)(NO(3))(3)测量的频率与在凝聚相中测量的频率相差几厘米(-1)，这是IRMPD与凝聚相吸收光谱比较中迄今取得的最佳一致性。此外，实验测定值与DFT计算预测值总体上吻合良好，特别是对于反对称UO(2)伸缩振动。将UO(2)(NO(3))(3)的光谱与Eu(NO(3))(4)的光谱进行比较，结果表明硝酸根与Eu(3+)金属中心的结合更强，这与其更高的电荷一致。还获得了一种具有元素组成UO(9)N(2)的独特铀酰-氧物种的光谱，该光谱包含暗示UO(2)(NO(3))(2)(O)结构的硝酸根吸收；该光谱缺乏指示亚硝酸根和超氧根的谱带，而这些谱带将指示另一种UO(2)(NO(3))(NO(2))(O(2))结构。
