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Dynamic fluxionality of ternary Mg2BeB8 cluster: a nanocompass

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A series of fluxional planar boron and boron-based binary clusters have evoked considerable interest of chemists. Here we propose the first ternary nanocompass cluster Mg2BeB8 based on quantum chemical calculations. It possesses a half-sandwich structure with a Mg2 dimer as the needle and a BeB8 molecular wheel as baseplate, which is the global minimum on the potential energy surface. Mg2BeB8 can be viewed as a nanocompass, whose Mg2 needle can rotate freely around the BeB8 baseplate at 300 K. The calculated rotation barrier is only 0.1 kcal mol−1 at the single-point CCSD(T)/6-311+G(d)//PBE0/6-311+G(d) level. Chemical bonding analyses indicate that Mg2BeB8 is a charge-transfer complex [Mg2]2+[BeB8]2− in nature. There is localized covalent Mg–Mg bond for [Mg2]2+ needle, while there are three delocalized π and three delocalized σ bonds for [BeB8]2− baseplate. The ionic bonding between the [Mg2]2+ needle and the 6π/6σ double aromatic [BeB8]2− baseplate makes the Mg2BeB8 cluster fluxional. The current results suggest that altering the baseplate is an effective way to enrich the nanocompass’ family.

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This work was supported by the National Natural Science Foundation of China (21873058), the Natural Science Foundation of Shanxi Province (201701D121033), and the Fund for Shanxi “1331 Project” Key Subjects Construction.

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Correspondence to Jin-Chang Guo.

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Zhang, X., Guo, J. Dynamic fluxionality of ternary Mg2BeB8 cluster: a nanocompass. J Mol Model 26, 30 (2020).

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  • Nanocompass
  • Half sandwich
  • Global minimum
  • Dynamic fluxionality
  • Chemical bonding
  • Double aromaticity