Encapsulation of a single electron within the internal cavity of a host system poses significant challenges, as the electron tends to delocalize over the surface. In this study, we successfully trap a single electron through a B–B one-electron σ-bond in a diborencine macrocycle (compound 4). The structure of this one-electron σ-bond has been characterized using X-ray single-crystal analysis and EPR studies, indicating that this bond exhibits considerable s-character, with the boron atoms adopting sp3 hybridization, as supported by DFT computations. Additionally, compound 4 demonstrates rich reactivity: it can facilitate O2 cleavage, generating a B–O–B cyclic product; its reaction with PhSSPh produces a B–S–B linked ring-expansion product, while reactions with PhSeSePh and quinone yield ring-contraction products. The resulting products have been fully characterized through X-ray single-crystal analysis, NMR, and HRMS spectroscopy. Finally, DFT computational studies have been performed to elucidate the reaction mechanism of this one-electron B–B bond.
Wu et al. (Sun,) studied this question.