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Periodic Trends in Actinyl Thio-Crown Ether Complexes

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journal contribution
posted on 19.02.2018, 18:49 by Shu-Xian Hu, Jing-Jing Liu, John K. Gibson, Jun Li
In-cavity complexes and their bonding features between thio-crown (TC) ethers and f-elements are unexplored so far. In this paper, actinyl­(VI) (An = U, Np, Pu, Am, and Cm) complexes of TC ethers have been characterized using relativistic density functional theory. The TC ether ligands include tetrathio-12-crown-4 (12TC4), pentathio-15-crown-5 (15TC5), and hexathio-18-crown-6 (18TC6). On the basis of the calculations, it is found that the “double-decker” sandwich structure of AnO2(12TC4)22+ and “side-on” structure AnO2(12TC4)2+ are changed to “insertion” structures for AnO2(15TC5)2+ and AnO2(18TC6)2+ due to increased size of the TC ether ligands. The actinyl monocyclic TC ether complexes are found to exhibit conventional conformations, with typical An–Oactinyl and An–Sligand distances and angles. Chemical bonding analyses by Weinhold’s natural population analysis (NPA), natural localized molecular orbital (NLMO), and energy decomposed analysis (EDA), show that a typical ionic An–Sligand bond with the extent of covalent interaction between the An and S atoms primarily attributable to the degree of radial distribution of the S 3p atomic orbitals. The similarity and difference of the oxo-crown and TC ethers as ligands for actinide coordination chemistry are discussed. As soft S-donor ligands, TC ethers may be candidate ligands for actinide recognition and extraction.