A series of novel fluorescent isomers were designed by using 5H‐indeno[1,2‐b]pyridin‐5‐one (IP) as electron acceptor and triphenylamine (TPA) as electron donor, and were synthesized through Suzuki coupling reactions. The substitution position of TPA on IP was adjusted to form 6‐(4‐(diphenylamino)phenyl)‐5H‐indeno[1,2‐b]pyridin‐5‐one (IP‐6‐TPA), IP‐7‐TPA, IP‐8‐TPA, and IP‐9‐TPA. The photophysical, thermal, and electrochemical properties of these isomers were systematically studied through experimental and theoretical methods. It was observed that the substitution position of TPA on IP results in different molecular conformation and finally determine the luminescent behavior of these isomers. The 6‐ and 9‐substituted isomers IP‐6‐TPA and IP‐9‐TPA with larger torsion angles exhibited thermally activated delayed fluorescence (TADF) feature with long fluorescence lifetimes of microsecond range, while another two isomers IP‐7‐TPA and IP‐8‐TPA are only normal fluorescent molecules. Relatively higher photoluminescence quantum yields were detected for IP‐6‐TPA (0.70) and IP‐8‐TPA (0.69), while IP‐7‐TPA is poor emissive (0.23). These isomers were used as doped emitters to fabricate organic light‐emitting diodes (OLEDs), among which IP‐6‐TPA realized the best performance with a maximum external quantum efficiency of 9.0% and a current efficiency of 24.2 cd A⁻¹.

中文翻译：

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取代对5H-茚并[1,2-b]吡啶-5-酮基异构体发光的影响

以5 H-茚并[1,2 - b ]吡啶-5-酮（IP）为电子受体，三苯胺（TPA）为电子供体，设计了一系列新型荧光异构体，并通过Suzuki偶联反应合成。调整TPA在IP上的取代位置，形成6-（4-（二苯氨基）苯基）-5 H-茚并[1,2- b] pyridin‐5‐one（IP‐6‐TPA），IP‐7‐TPA，IP‐8‐TPA和IP‐9‐TPA。通过实验和理论方法系统地研究了这些异构体的光物理，热和电化学性质。观察到TPA在IP上的取代位置导致不同的分子构象，并最终确定这些异构体的发光行为。扭转角较大的6和9取代异构体IP-6-TPA和IP-9-TPA具有热激活延迟荧光（TADF）功能，荧光寿命长于微秒范围，而另两个异构体IP-7-TPA和IP-7 IP-8-TPA只是正常的荧光分子。IP-6-TPA（0.70）和IP-8-TPA（0.69）的光致发光量子产率相对较高，而IP-7-TPA的发射率较低（0.23）。^-1。