Thorium and Uranium Carbide Cluster Cations in the Gas Phase: Similarities and Differences between Thorium and Uranium

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• 作者：Cl谩udia C. L. Pereira ; R茅mi Maurice ; Ana F. Lucena ; Shuxian Hu ; Ant贸nio P. Gon莽alves ; Joaquim Mar莽alo ; John K. Gibson ; Lester Andrews ; Laura Gagliardi
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：October 7, 2013
• 年：2013
• 卷：52
• 期：19
• 页码：10968-10975
• 全文大小：312K
• 年卷期：v.52,no.19(October 7, 2013)
• ISSN：1520-510X

文摘

Laser ionization of AnC₄ alloys (An = Th, U) yielded gas-phase molecular thorium and uranium carbide cluster cations of composition An_mC_np>+p>, with m = 1, n = 2鈥?4, and m = 2, n = 3鈥?8, as detected by Fourier transform ion-cyclotron-resonance mass spectrometry. In the case of thorium, Th_mC_np>+p> cluster ions with m = 3鈥?3 and n = 5鈥?0 were also produced, with an intriguing high intensity of Th₁₃C_np>+p> cations. The AnC₁₃p>+p> ions also exhibited an unexpectedly high abundance, in contrast to the gradual decrease in the intensity of other AnC_np>+p> ions with increasing values of n. High abundances of AnC₂p>+p> and AnC₄p>+p> ions are consistent with enhanced stability due to strong metal鈥揅₂ bonds. Among the most abundant bimetallic ions was Th₂C₃p>+p> for thorium; in contrast, U₂C₄p>+p> was the most intense bimetallic for uranium, with essentially no U₂C₃p>+p> appearing. Density functional theory computations were performed to illuminate this distinction between thorium and uranium. The computational results revealed structural and energetic disparities for the An₂C₃p>+p> and An₂C₄p>+p> cluster ions, which elucidate the observed differing abundances of the bimetallic carbide ions. Particularly noteworthy is that the Th atoms are essentially equivalent in Th₂C₃p>+p>, whereas there is a large asymmetry between the U atoms in U₂C₃p>+p>.