Late-Stage Functionalization of a Hexa-peri-Benzocoronene-Fluoranthene Hybrid Influenced by Dynamic Inversion of...

The functionalization of a hexa-peri-benzocoronene-fluoranthene hybrid with a K-type bay region is investigated. Bromination proceeds regioselectively at two peripheral positions, which contradicts the electronic and structural predictions suggesting that substitution at the K-type bay region should be favored. Computational studies reveal that the transition state and intermediate energies for all substitution positions are comparable, though no substitution in the bay region is observed. To rationalize this unexpected regioselectivity, a model is proposed based on dynamic helical inversion, which prevents the corresponding Wheland intermediates from being stabilized. Subsequent conversion of the brominated compounds to nitrile derivatives affords compounds with photoluminescence quantum yields of up to 76% in solution. Organic light-emitting diodes with luminance values of up to 6,500 cd·m^-2 are realized due to the effective energy level alignment by a hole-transport and electron-blocking layer, which was not possible with the related nonfunctionalized derivative.