Bis-Boron/Nitrogen-Doped Azaullazines: Synthesis, Structures, and Their Emitting Properties

We herein report a concise three-step sequence to construct three BN-doped azaullazines ( BNAzaU-1, BNAzaU-2, and BNAzaU-3 ) with bee-shaped structural features. The synthesis includes (ii) Clauson-Kaas pyrrole cyclization, (ii) Buchwald-Hartwig C–N coupling, and (iii) electrophilic borylation reactions. Single-crystal X-ray diffraction analysis unambiguously confirms the highly planarized, rigid π-conjugated framework of the core of BN-doped azaullazine. All three BN-doped azaullazines demonstrate characteristic dual emission originating from both localized excited state (short wavelength) and charge-transfer state (long wavelength). In specific, BNAzaU-1 exhibits superior photoluminescent properties with a high quantum yield. We fabricated three solution-processed OLEDs by employing BNAzaU-1, BNAzaU-2, and BNAzaU-3 as emissive layers. All OLEDs show broadband emission spectra, and the BNAzaU-1 -based OLED achieves premium electroluminescent performance with a maximum luminance of 2218 cd m –2 and an external quantum efficiency of 1.31%, which shows significant potential in solid-state lighting.