Cage-like B40C30, B40C40, and B40C50: high-symmetry heterofullerenes isovalent with C60, C70, and C80.

The recent discovery of the cage-like borospherenes B40-/0, composed of interwoven double chains of boron, presents the possibility of forming BmCn heterofullerenes as hybrids of borospherenes and carbon fullerenes in dual spaces. Based on extensive first-principles theory calculations, we predict herein the possible existence of the high-symmetry BmCn heterofullerenes S10 B40C30 (1), C5 B40C40 (2), and S10 B40C50 (3), which are isovalent with C60, C70, and C80, respectively. These beautiful borafullerenes with boron aggregations feature one B30 boron double-chain nanoring at the equator, two bowl-shaped C15 or C25 caps at the top and bottom, and ten quasi-planar tetracoordinate peripheral C atoms in ten B-centered B6C hexagonal pyramids that are evenly distributed around the waist in a seamless "patched" structural motif. Detailed orbital and bonding analyses indicate that, as they are isovalent with C60, C70, and C80, respectively, B40C30 (1), B40C40 (2), and B40C50 (3) possess 30, 35, and 40 π bonds, respectively, of which 20 are 5c-2e π bonds delocalized over ten hexagonal pyramids that are evenly distributed around the waist. Such structural and bonding patterns confer high stability to these B-C heterofullerenes, which may be synthesized in experiments.