Theoretical probing of twenty-coordinate actinide-centered boron molecular drums

The exploration of metal-doped boron clusters has a great significance in the design of high coordination number (CN) compounds. Actinide-doped boron clusters are probable candidates for achieving high CNs. In this work, we systematically explored a series of actinide metal atom (U, Np, and Pu) doped B 20 boron clusters An@B 20 (An = U, Np, and Pu) by global minimum structural searches and density functional theory (DFT). Each An@B 20 cluster is confirmed to be a twenty-coordinate complex, which is the highest CN obtained in the chemistry of actinide-doped boron clusters so far. The predicted global minima of An@B 20 are tubular structures with actinide atoms as centers, which can be considered as boron molecular drums. In An@B 20 , U@B 20 has a relatively high symmetry of C 2 , while both Np@B 20 and Pu@B 20 exhibit C 1 symmetry. Extensive bonding analysis demonstrates that An@B 20 has σ and π delocalized bonding, and the U-B bonds possess a relatively higher covalency than the Np-B and Pu-B bonds, resulting in the higher formation energy of U@B 20 . Therefore, the covalent character of An-B bonding may be crucial for the formation of these high CN actinide-centered boron clusters. These results deepen our understanding of actinide metal doped boron clusters and provide new clues for developing stable high CN boron-based nanomaterials. DFT calculations demonstrated that An@B 20 (An = U, Np, and Pu) are twenty-coordinated boron molecular drums, and the An-B bond covalency dominates the stability.