Stable Open-Shell Bowl-Shaped Cycloarene with Multiple Hybrid Spin–Spin Coupling and Tunable Radical Characters

The precise syntheses of well-defined cycloarenes and stable open-shell polyradicaloids are two challenging topics in chemistry and materials science. Herein, the first example of a cycloarene polyradicaloid molecule (CPR) with three types of adjacent spin–spin coupling was successfully synthesized in single-crystal form by fusing Chichibabin, Schlenk, and o-quinodimethane hydrocarbons into a conjugated double-stranded bowl structure. It exhibits a small singlet–triplet energy gap, significant polyradical characters, and remarkable stability (t1/2 = 110 days in air-saturated solution). Interestingly, CPR adapts a rigid oval-bowl-shaped configuration and demonstrates fascinating encapsulation of fullerenes C60 and C70. Crucially, various experimental results confirm that the intramolecular spin–spin interactions can be effectively modulated by an electron-accepting guest, which represents the first systematic study of the radical characters in π-conjugated polyradicaloids by a supramolecular assembly strategy. Our findings provide a new approach for constructing stable cycloarene polyradicaloids and a novel strategy for manipulating radical spin coupling.