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Counter-Intuitive Stability in Actinide-Encapsulated Metalloid Clusters with Broken Aromaticity

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journal contribution
posted on 27.08.2018 by Meenakshi Joshi, Ayan Ghosh, Aditi Chandrasekar, Tapan K. Ghanty
Aromaticity has been traditionally used for decades to explain the exceptional stability of certain conjugated organic compounds. Only in the recent past, this concept has crossed the bounds of organic chemistry and been employed in understanding inorganic ring systems with conjugation. In the present work, actinide element-doped E126– (E = Sb, Bi) clusters formed from the combination of an actinide ion and aromatic Bi42– or Sb42– rings are thoroughly investigated using density functional theory to explore their geometric, electronic and bonding properties in comparison with the bare cluster. The aromatic E42– rings in the bare clusters lost their aromaticity due to loss in planarity of the E42– rings on interaction with the central atom/ion. Although the extent of nonplanarity of the three E42– rings is increased considerably on moving along the valence-isoelectronic series, Th4+–Pa5+–U6+–Np7+ in the doped clusters, the stability of the clusters is increased significantly. Valence-isoelectronic lanthanide ion-doped metalloid clusters, viz., La3+, Ce4+, Pr5+, and Nd6+ have also been investigated for the sake of comparison, among which experimental and theoretical study of [La­(η4-Sb4)3]3– cluster has been reported recently. The highlight of the entire investigation is that the metal atom/ion-doped clusters, nevertheless, displayed higher stability than the bare clusters in spite of losing their valuable aromatic stabilization. The various factors responsible for the stability of the lanthanide- and actinide-doped nonaromatic clusters including electronic shell-closing are elucidated in the present research.