An Olefin Radical Based Thiele′s Hydrocarbon Derivative and Macrocyclic Tetraradical

A persistent Thiele′s hydrocarbon derivative, containing two five‐membered dioxoborocyclic monoradical units bridged by a p‐phenylene, was generated. It exhibits an open‐shell singlet ground state with a large singlet−triplet energy gap. A macrocyclic molecule, composed of two units of the Thiele′s hydrocarbon derivative, was also prepared. The macrocyclic molecule possesses an open‐shell singlet ground state but with considerable tetraradical character. The diradical and tetraradical compounds can be viewed as a zwitterionic species containing olefin radical cations. These newly formed compounds are stable both in the solid state and solution under inert atmosphere for several days. They have been fully investigated by single‐crystal X‐ray diffraction, NMR, EPR and UV‐Vis spectroscopy, and SQUID measurements, as well as theoretical calculations.