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

Abstract

AbstractA 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.