Polycyclic Aromatic Hydrocarbons with a Boron‐Doped Zigzag/Armchair Topology: A Boron‐Edging Strategy for Organic Narrowband Emitters

Control over molecular topologies and/or heteroatom doping of polycyclic aromatic hydrocarbons (PAHs) may alter their electronic structures and achieve desirable physical properties. Herein, this work challenges boron-doping and edge-transformation of π-extended PAHs. We successfully synthesized a series of large-size PAHs featuring a boron-doped zigzag/armchair edge topology through one-pot multifold Scholl cyclization reaction. Two of them possess the desired C₃-symmetric and unexpected unsymmetrical C₅₄B₃ nanographene frameworks, respectively, thus illustrating triply boron-edging manipulations of hexa-peri-hexabenzocoronene. Detailed studies reveal that such boron-doped edge topology significantly inhibits their excited-state molecular vibrations and thereby produces narrowband emission characteristics. The full width at half maximum (FWHM) values of their fluorescence spectra are as small as 12-18 nm, which have never been observed for pristine boron-doped π-system and are among the smallest values reported for organic emitters. Their solution-processed organic light-emitting diodes (OLEDs) display extremely narrowband electroluminescence, and additionally, the obtained FWHM of only 23 nm represents the narrowest one reported for red OLEDs.