1898-74-4Relevant articles and documents
Expanding the hole delocalization range in excited molecules for stable organic light-emitting diodes employing thermally activated delayed fluorescence
Ai, Qi,Cao, Fangyi,Deng, Chao,Liu, Zhang,Su, Liwu,Tsuboi, Taiju,Wang, Chao,Wang, Dan,Zhang, Qisheng,Zheng, Xinyuan,Zhu, Yunhui
, p. 10021 - 10030 (2020)
Metal-free, thermally activated delayed fluorescent (TADF) emitters have emerged as a promising new generation of organic light-emitting diode (OLED) materials. Donor-acceptor (D-A) structures are widely used in TADF molecular design to ensure a small energy splitting between the singlet and triplet excitons. Here, a series of efficient bluish-green TADF emitters are constructed using one or two phenyltriazine acceptors and one tercarbazole, bicarbazole or indolo[2,3-b]carbazole donor through an ortho-linkage. The impact of the D/A ratio on the photoluminescence and electroluminescence stability of these emitters in doped films is thoroughly investigated. According to the two-exciton dynamics and the degradation products, device degradation is deduced to be a result of electrophilic substitution between two charge-transfer excitons. Within a limited molecular weight range, increasing the number of acceptor moieties leads to a decrease in the hole delocalization range in the excited state, which facilitates the substitution reaction. Based on an optimized device structure, the device containing an emitter with bulk a tercarbazole donor achieves a long half-life of 1512 hours with an initial luminescence of 1000 cd m-2. Our findings reveal a possible mechanism for exciton-exciton and exciton-polaron annihilation-induced device degradation and provide new approaches for achieving stable OLEDs employing TADF.
New Strategy for the Synthesis of Heterocycles via Copper-Catalyzed Oxidative Decarboxylative Amination of Glyoxylic Acid
Niu, Bin,Li, Shaoqing,Cui, Chang,Yan, Yizhe,Tang, Lin,Wang, Jianyong
supporting information, p. 7800 - 7803 (2019/11/28)
A copper-catalyzed oxidative decarboxylative amination of glyoxylic acid with substrates having two nitrogen-nucleophilic sites was first demonstrated. Using this novel approach, 1,3,5-triazines, quinazolinones and quinazolines were obtained in up to 93 % yields. Notably, glyoxylic acid was employed as the C1 synthon for heterocycles. This strategy enriches the application of glyoxylic acid for the synthesis of valuable heterocycles.
Transition metal-free assembly of 1,3,5-triazines using ethyl bromodifluoroacetate as C1 source
Yu, Xiaoxia,Zhou, Yao,Ma, Xingxing,Song, Qiuling
supporting information, p. 8079 - 8082 (2019/07/15)
An efficient transition metal-free annulation of amidine with ethyl bromodifluoroacetate to access 2,4-disubstituted-1,3,5-triazines is firstly presented. The desired symmetric and unsymmetric 2,4-disubstituted-1,3,5-triazines were obtained in decent yields via multiple C-N bond formation, in which ethyl bromodifluoroacetate is harnessed as a unique C1 synthon via quadruple cleavage. This reaction is transition metal-free, oxidant-free and simple in operation, and only lowly toxic inorganic wastes are generated.