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

Laser ionization of AnC4 alloys (An = Th, U) yielded gas-phase molecular thorium and uranium carbide cluster cations of composition An m C n +, with m = 1, n = 2–14, and m = 2, n = 3–18, as detected by Fourier transform ion-cyclotron-resonance mass spectrometry. In the case of thorium, Th m C n + cl...

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Published in:Inorganic chemistry 2013-10, Vol.52 (19), p.10968-10975
Main Authors: Pereira, Cláudia C. L, Maurice, Rémi, Lucena, Ana F, Hu, Shuxian, Gonçalves, António P, Marçalo, Joaquim, Gibson, John K, Andrews, Lester, Gagliardi, Laura
Format: Article
Language:English
Subjects:
Chemical Sciences
or physical chemistry
Theoretical and
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Summary:Laser ionization of AnC4 alloys (An = Th, U) yielded gas-phase molecular thorium and uranium carbide cluster cations of composition An m C n +, with m = 1, n = 2–14, and m = 2, n = 3–18, as detected by Fourier transform ion-cyclotron-resonance mass spectrometry. In the case of thorium, Th m C n + cluster ions with m = 3–13 and n = 5–30 were also produced, with an intriguing high intensity of Th13C n + cations. The AnC13 + ions also exhibited an unexpectedly high abundance, in contrast to the gradual decrease in the intensity of other AnC n + ions with increasing values of n. High abundances of AnC2 + and AnC4 + ions are consistent with enhanced stability due to strong metal–C2 bonds. Among the most abundant bimetallic ions was Th2C3 + for thorium; in contrast, U2C4 + was the most intense bimetallic for uranium, with essentially no U2C3 + 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 An2C3 + and An2C4 + cluster ions, which elucidate the observed differing abundances of the bimetallic carbide ions. Particularly noteworthy is that the Th atoms are essentially equivalent in Th2C3 +, whereas there is a large asymmetry between the U atoms in U2C3 +.
ISSN:0020-1669
1520-510X
DOI:10.1021/ic401058b