Bis‐Olefin Based Crystalline Schlenk Hydrocarbon Diradicals with a Triplet Ground State

A modular approach for the synthesis of isolable crystalline Schlenk hydrocarbon diradicals from m ‐phenylene bridged electron‐rich bis‐triazaalkenes as synthons is reported. EPR spectroscopy confirms their diradical nature and triplet electronic structure by revealing a half‐field signal. A computational analysis confirms the triplet state to be the ground state. As a proof‐of‐principle for the modular methodology, the 4,6‐dimethyl‐ m ‐phenylene was further utilized as a coupling unit between two alkene motifs. The steric conjunction of the 4,6‐dimethyl groups substantially twists the substituents at the nonbonding electron bearing centers relative to the central coupling m ‐phenylene motif. As a result, the spin delocalization is decreased and the exchange coupling between the two unpaired spins, hence, significantly reduced. Notably, 108 years after Schlenk's m ‐phenylene‐bis(diphenylmethyl) synthesis as a diradical, for the first time we were able to isolate its derivative with the same spacer, i.e. m ‐phenylene, between two radical centers in a crystalline form.