Sea-shell-like B31+ and B32: two new axially chiral members of the borospherene family

Since the discovery of the cage-like borospherenes D-2d B-40(-/0) and the first axially chiral borospherenes C-3/C-2 B-39(-), a series of fullerene-like boron clusters in different charge states have been reported in theory. Based on extensive global minimum searches and first-principles theory calculations, we present herein two new axially chiral members C-2 B-31(+) (I) and C-2 B-32 (VI) to the borospherene family. B-31(+) (I) features two equivalent heptagons on the top and one octagon at the bottom on the cage surface, while B-32 (VI) possesses two equivalent heptagons on top and two equivalent heptagons at the bottom. Detailed bonding analyses show that both sea-shell-like B-31(+) (I) and B-32 (VI) follow the universal sigma + pi double delocalization bonding pattern of the borospherene family, with ten delocalized pi bonds over a sigma skeleton, rendering spherical aromaticity to the systems. Extensive molecular dynamics simulations show that these novel borospherenes are kinetically stable below 1000 K. The IR, Raman, and UV-vis spectra of B-31(+) (I) and B-32 (VI) are computationally simulated to facilitate their future experimental characterizations.