Formation of the quasi-planar B-50 boron cluster: topological path from B-10 and disk aromaticity

摘要

The lowest-lying isomer of the B-50 boron cluster is confirmed to have a quasi-planar shape with two hexagonal holes. By applying a topological (leap-frog) dual operation followed by boron capping, we demonstrated that such a quasi-planar structure actually comes from the smallest elongated B-10(2-), and its high thermodynamic stability is due to its inherent disk aromaticity arising from its 32 valent electrons that fully occupy a disk configuration of [(1 sigma)(2)(1 pi)(4)(1 delta)(4)(2 sigma)(2)(1 phi)(4)(2 pi)(4)(1 gamma)(4)(2 delta)(4)(1 eta)(4)]. The aromatic character of the quasi-planar B-50 is further supported by a strong diatropic magnetic current flow. The sudden appearance of a quasi-planar B-50 again points out that the growth pattern of pure boron clusters is still far from being completely understood.