Substitution effect on solid parking motif and luminescence of diphenylfuro[2,3-b]quinoxaline isomers

The organic molecules combining light-emitting and charge-transporting property are highly expected. We designed and synthesized a pair of isomers, 2,6-diphenylfuro[2,3-b]quinoxaline (26dPFQ) and 2,7-diphenylfuro[2,3-b]quinoxaline (27dPFQ), and investigated effect of changing substituent position on molecule packing motif, conducting and luminescence feature of resulting materials. In CH₂Cl₂ solution, both isomers, 26dPFQ and 27dPFQ, emit deep blue light with a wavelength of 422 nm and shows photoluminance quantum yield (PLQY) of 58.9% and 48.7%, respectively. In crystal, the 26dPFQ employs H-type packing motif and retains blue florescent emission with low PLQY (10.0%) while 27dPFQ adopts J-aggregated packing motif and shows enhanced green fluorescent emission with a PLQY of 55.0%. The organic light-emitting devices for both emitters show deep blue emission, the EL peak at 410 nm for 26dPFQ and 424 nm for 27dPFQ, and respectively presents the maximum EQE of 1.2% and 1.0%. The 26dPFQ shows better charge transport capability over 27dPFQ. Our results suggested 2,6-substitution on furo[2,3-b]quinoxaline core are expected to afford such dual functional materials.