Redox-Active Lewis Pairs Yield Diradicaloids and Enable Modular Control of the Diradical Character.

Stable metal-free diradicaloids are fascinating compounds, typically based on covalent polycyclic or nitrogen-containing π-conjugated frameworks. Unfortunately, their preparation and the modulation of their diradical character require substantial synthetic efforts. The present work introduces a synthetic approach to diradicaloids by the ease and modularity of Lewis pair formation. Binding redox-active bis(catecholato)silane Lewis acids to ditopic tetraoxolene Lewis bases yields adducts with varying spin ground states. Computational analyses disclose that the diradical character increases with the electron donor ability of the catechols and the electron accepting ability of the tetraoxolene. Hence, this protocol grants access to diradicaloids with rationally adjustable diradical character of high potential for numerous applications in a single step.