Phenanthrene-Fused BN-Acenaphth(yl)ene: Synthesis, Structures, and Photophysical Studies

Two novel BN-doped CP-PAHs, BN-ANH-TPh and BN-AN-TPh, were synthesized in a straightforward manner. BN-ANH-TPh features a localized C–C bond in the five-membered ring, whereas BN-AN-TPh features a localized CC bond. Notably, BN-AN-TPh was obtained via the dehydrogenation of BN-ANH-TPh. Both compounds were unambiguously characterized by single-crystal X-ray diffraction analysis. A subtle structural alteration from C–C to CC bonding resulted in significant modulation of their electronic structures and photophysical properties. Compared to BN-ANH-TPh, BN-AN-TPh exhibits lower LUMO and HOMO energy levels, accompanied by a narrower HOMO–LUMO energy gap. BN-AN-TPh exhibits red-shifted absorption and emission spectra relative to those of BN-ANH-TPh. Both compounds emit strongly in solution, with quantum yields of 73% and 71%, respectively. Furthermore, organic light-emitting diodes (OLEDs) were fabricated by using BN-AN-TPh and BN-ANH-TPh as emissive layers. The OLED device based on BN-AN-TPh achieved a maximum current efficiency of 2.41 cd/A and a maximum luminance of 1556 cd/m2.