Emission spectroscopy of uranium(IV) compounds: a combined synthetic, spectroscopic and computational study
Emission spectroscopy of uranium(IV) compounds: a combined synthetic, spectroscopic and computational study
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DOI：
10.1039/c3ra22712j
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发表时间：
2013-01-01
期刊：
影响因子：
3.9
通讯作者：
Baker, Robert J.
中科院分区：
文献类型：
--
作者：
Hashem, Emtithal;Swinburne, Adam N.;Baker, Robert J.
发射光谱首次用于非水介质中铀（IV）卤化物络合物的光谱研究。本文报道了简单配合物[Li（THF）（4）][UX_5（THF）]（X = Cl，Br，I），[Et_4N]（2）[UCl_6]和UCl_4在THF中的室温电子吸收光谱，并利用CASSCF和CASPT_2技术对所有跃迁进行了全面的计算归属。激发到f-d和LMCT特征的带中，然后能量转移到5 f轨道流形中，解释了在发射光谱中观察到的UV-可见辐射跃迁，其已被完全指定为从5 f（1）6d（1）电子构型到基态5 f（2）构型产生的状态包络的跃迁。[Li（THF）（4）][UCl 5（THF）]中的成键已利用NBO和AIM计算进一步阐明，NBO和AIM计算描述了U-Cl键的性质，其主要是离子键，具有一些配价共价特征，并且Cl 3 p轨道与铀上的5 f和6d轨道之间存在大量重叠。这些研究表明，具有O-h、C-4v和C-2 v对称性的简单U（IV）化合物的发射光谱指纹具有相似性和特征性，可作为一种诊断工具，在[UO 2]（2+）存在的情况下，对溶液中的U（IV）物种进行归属，并通过推断对环境中的U（IV）物种进行归属。
Emission spectroscopy has been used for the first time in a spectroscopic study of a family of uranium(IV) halide complexes in non-aqueous media. The room temperature electronic absorption spectra of the simple coordination compounds [Li(THF)(4)][UX5(THF)] (X = Cl, Br, I), [Et4N](2)[UCl6] and UCl4 in THF have been recorded and all transitions assigned with the aid of a comprehensive computational study using CASSCF and CASPT2 techniques. Excitation into a band of f-d and LMCT character followed by energy transfer into the 5f-orbital manifold accounts for the UV-visible radiative transitions observed in the emission spectra, which have been fully assigned as arising from transitions from the 5f(1)6d(1) electronic configuration to envelopes of states arising from the ground state 5f(2) configuration. The bonding in [Li(THF)(4)][UCl5(THF)] has been further elucidated utilising NBO and AIM calculations which describe the nature of the U-Cl bond as predominantly ionic with some dative covalent character and substantial overlap between the Cl 3p orbitals and 5f and 6d orbitals on uranium. These studies indicate that the emission spectral fingerprint of simple U(IV) compounds of O-h, C-4v and C-2v symmetry are similar and characteristic and may be used as a diagnostic tool to assign U(IV) species in solution and by inference, in the environment, in the presence of [UO2](2+).