Developing new electron acceptors with high rigidity and structural adjustability is significant for realizing efficient long-wavelength thermally activated delayed fluorescence (TADF) emitters. Herein, a new acceptor group, acenaphtho[1,2-b]quinoxaline-3,4-dicarbonitrile (AQCN), featuring a π-extended, rigid skeleton with high electron affinity, is developed for the construction of red TADF dyes. Two red light-emitting regioisomers, LB-Y and LB-T, featuring a Y-shape and T-shape D-A-D molecular configuration, respectively, were prepared by adjusting the relatively substituting position of two triphenylamine electron-rich moieties on AQCN. Through the isomeric engineering, it is found that LB-Y shows a high degree of molecular rigidity, matched excited-state energy level alignment, and decent interplay among singlet charge transfer excited state (¹CT), triplet locally excited state (³LE) and triplet hybridized local and charge transfer excited state (³HLCT). Therefore, LB-Y has a higher radiative transition rate (8.36 × 10⁷ s⁻¹), reverse intersystem crossing rate (1.02 × 10⁵ s⁻¹), and better electroluminescent performances (λEL = 614 nm, EQE_max = 4.1%) than LB-T (λ_EL = 612 nm, EQE_max = 2.6%). This study reports a promising electron acceptor and provides an efficient approach to modulating the optoelectronic properties of red TADF dyes.

开发具有高刚性和结构可调性的新型电子受体对于实现高效的长波长热激活延迟荧光（TADF）发射器具有重要意义。在此，开发了一种新的受体基团苊并 [1,2- b ] 喹喔啉-3,4-二腈 (AQCN)，具有 π 扩展的刚性骨架和高电子亲和力，用于构建红色 TADF 染料。通过调整两个三苯胺富电子基团在AQCN上的相对取代位置，制备了两种红色发光区域异构体LB -Y和LB-T ，分别具有Y型和T型DAD分子构型。通过异构工程发现LB-Y显示出高度的分子刚性、匹配的激发态能级排列以及单线态电荷转移激发态 ( ¹ CT)、三线态局部激发态 ( ³ LE) 和三线态杂化局部和电荷转移激发态 ( ³ HLCT)之间的良好相互作用). 因此，LB-Y具有更高的辐射跃迁率(8.36 × 10 ⁷ s ⁻¹ )、反向系间穿越率(1.02 × 10 ⁵ s ⁻¹ )和更好的电致发光性能( λ EL  = 614 nm, EQE _max  = 4.1 %) 比LB-T ( λ _EL  = 612 nm, EQE_最大值 = 2.6%)。这项研究报告了一种有前途的电子受体，并提供了一种有效的方法来调节红色 TADF 染料的光电特性。