Unveiling the Centrosymmetric\nEffect in the Design\nof Narrowband Fluorescent Emitters: From Single to Double Difluoroboron\nCores

Narrowband fluorescent emitters are receiving significant\nattention\ndue to the great potential for creating ultrahigh-definition organic\nlight-emitting diode displays (UHD-OLED). Unveiling innovative mechanisms\nto design new high-performance narrowband fluorescent emitters is\na concerted endeavor in both academic and industrial circles. Theoretical\ncalculations reveal that the centrosymmetric dianilido-bipyridine\nboron difluoride framework (<i>cs</i>-DAPBF<sub>2</sub>)\nexhibits significantly reduced structural relaxation compared to previously\nreported asymmetric structures with monofluoroboron cores, creating\nnew opportunities for the development of narrowband fluorescent emitters.\nIn this work, we present a dual chelation-assisted C–H/C–H\nhomocoupling strategy to efficiently synthesize the 3,3′-amino-2,2′-bipyridine\nskeleton, enabling the straightforward construction of a series of\nsymmetric <i>cs</i>-DAPBF<sub>2</sub>-based fluorescent\nemitters. Through molecular optimization, we have developed a high-performance\nnarrowband green fluorescent emitter, <i>cs</i>-DMeAPBF<sub>2</sub>-MP, which demonstrates a narrow full width at half-maximum\n(fwhm) of 20 nm, a high photoluminescence quantum yield (Φ<sub>PL</sub>) of 98%, a large molar absorptivity (ε) of 2.10 ×\n10<sup>4</sup> M<sup>–1</sup> cm<sup>–1</sup>, and a\nhigh horizontal dipole ratio (Θ<sub>//</sub>) of 77%. These\nproperties make <i>cs</i>-DMeAPBF<sub>2</sub>-MP a promising\ncandidate for fabricating high-efficiency, narrowband green organic\nlight-emitting diodes (OLEDs) with minimal efficiency roll-off. This\nstudy represents the first successful application of the DAPBF<sub>2</sub> architecture in the design of narrowband fluorescent emitters\nfor high-performance OLEDs.