A Boron-Doped Buckybowl with a C₄₂B₂ Core: Synthesis, Crystal Structure, and Optoelectronic Properties

Constructing curved topologies of and/or doping heteroatoms into molecular carbons are of importance for synthetic chemistry and materials science. Herein, we disclose a boron-doped buckybowl, which was realized by region-cyclization-induced curvature of an organoboron π-system. Its synthesis was enabled by consecutive alkyne-based annulation and palladium-catalyzed regional C-H arylation. This molecule features a C₄₂B₂ polycyclic π-skeleton containing two pentagonal rings, and has a highly stable bowl-shaped geometry, thus representing an unprecedented kind of curved heterocyclic molecular carbons. Notably, a few unexpected photophysical properties were achieved, including narrowband red fluorescence, stimulated emission, and amplified spontaneous emission. All of these properties have never been reported in other all-carbon and heterocyclic buckybowls, and demonstrate that such boron-doped buckybowls are promising for use as narrowband emitters and optical-gain materials. Additionally, it shows a four-step reversible reduction activity, revealing its efficient electron-accepting capability contributed by the boron atoms and pentagonal rings.