Reversible Interconversion between a Carbon–Carbon Double Bond and Diradical beyond External Stimulus

The reversible interconversion between a carbon–carbon double bond and a diradical species represents a fundamental challenge in organic chemistry, with implications for molecular design and electronic materials. While steric strain and external stimulus can induce partial twisting of a carbon–carbon double bond, achieving stable diradical states through controlled, reversible bond twisting remains a significant challenge. Here, we report a strategy in which Lewis acid coordination enables the controlled twisting of C═C bonds to form diradical species with torsional angles of over 70°. Through coordination of Al(OR F ) 3 (R F = C(CF 3 ) 3 ) or SiEt 3 + to bianthrone derivatives, we isolate twisted adducts characterized by X-ray crystallography, EPR spectroscopy, and magnetic studies. The process is reversible─competitive displacement of Lewis acids by CH 3 CN restores folded alkenes, as monitored by UV–vis and NMR spectroscopy. This work provides a strategy for manipulating carbon–carbon double-bond topology with potential applications in reversibly responsive molecular systems.