RESUMO
We report on the fluorescence properties of a new class of emissive and stable π-radicals that contain a boron atom at a position distant from the radical center. A fully planarized derivative exhibited an intense red fluorescence with high fluorescence quantum yields (ΦF >0.67) even in polar solvents. To elucidate the origin of this phenomenon, we synthesized another boron-stabilized radical that contains a bulky aryl group on the boron atom. A comparison of these derivatives, as well as with conventional donor-π-acceptor (D-π-A)-type emissive π-radicals, unveiled several characteristic features in their photophysical properties. A theoretical analysis revealed that the SOMO-LUMO electronic transition generates an emissive D1 state. Unlike conventional D-π-A-type π-radicals, this state does not undergo significant structural relaxation. The boron-stabilized π-radicals demonstrated promising potential for organic light-emitting diodes as an emitting material.
RESUMO
Organic neutral π-monoradicals are promising semiconductors with balanced ambipolar carrier-transport abilities, which arise from virtually identical spatial distribution of their singly occupied and unoccupied molecular orbitals, SOMO(α) and SOMO(ß), respectively. Herein, we disclose a boron-stabilized triphenylmethyl radical that shows outstanding thermal stability and resistance toward atmospheric conditions due to the substantial spin delocalization. The radical is used to fabricate organic Mott-insulator transistors that operate at room temperature, wherein the radical exhibits well-balanced ambipolar carrier transport properties.
