Spherical Trihedral Metallo-Borospherene with Asymmetric Triangles in Boron Framework

The recent discovery of spherical trihedral metallo-borospherenes Ln3B18− (Ln = La, Tb) represents the onset of an unprecedented class of boron-metal binary nanomaterials, where heterogeneous La or Tb atoms, alongside B atoms, constitute integral components of the outer cage surface. Here, C3v A1-Sc3B16+ is theoretically predicted as the global minimum by the particle swarm optimization (PSO) algorithm, and its B16-framework comprises unequal B6 and B7 triangles, connected by three B atoms between the vertexes of the B6 triangle and the interval edges of the B7 triangle. This arrangement forms three equivalent η7-B7 rings, each centered with a Sc atom. The cage surface of the second low-lying A2 isomer features an asymmetric triangle of B3 and B7, along with three B2-linked units. This configuration gives rise to three equivalent octacoordinated Sc atoms, each centered within η8-B8 rings. These two cationic isomers have been proven to be very stable in kinetics and thermodynamics. Our findings regarding unequal boron triangles and smaller odd-coordinated rings in the B-framework enrich the geometric patterns of trihedral metallo-borospherenes.