Cage-like BC, BC, and BC: high-symmetry heterofullerenes isovalent with C, C, and C.

The recent discovery of the cage-like borospherenes B, composed of interwoven double chains of boron, presents the possibility of forming BC 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 BC heterofullerenes S BC (1), C BC (2), and S BC (3), which are isovalent with C, C, and C, respectively. These beautiful borafullerenes with boron aggregations feature one B boron double-chain nanoring at the equator, two bowl-shaped C or C caps at the top and bottom, and ten quasi-planar tetracoordinate peripheral C atoms in ten B-centered BC 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 C, C, and C, respectively, BC (1), BC (2), and BC (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.