Fiodorova Irina, Serevičius Tomas, Skaisgiris Rokas, Juršėnas Saulius, Tumkevicius Sigitas
Institute of Chemistry, Vilnius University, Naugarduko 24, LT-03225, Vilnius, Lithuania.
Institute of Photonics and Nanotechnology, Vilnius University, Saulėtekio 3, LT-10257 Vilnius, Lithuania.
Beilstein J Org Chem. 2022 May 5;18:497-507. doi: 10.3762/bjoc.18.52. eCollection 2022.
The interest in organic materials exhibiting thermally activated delayed fluorescence (TADF) significantly increased in recent years owing to their potential application as emitters in highly efficient organic light emitting diodes (OLEDs). Simple modification of the molecular structure of TADF compounds through the selection of different electron-donating or accepting fragments opens great possibilities to tune the emission properties and rates. Here we present the synthesis of a series of novel pyrimidine-carbazole emitters and their photophysical characterization in view of effects of substituents in the pyrimidine ring on their TADF properties. We demonstrate that electron-withdrawing substituents directly connected to the pyrimidine unit have greater impact on the lowering of the energy gap between singlet and triplet states (Δ ) for efficient TADF as compared to those attached through a phenylene bridge. A modification of the pyrimidine unit with CN, SCH, and SOCH functional groups at position 2 is shown to enhance the emission yield up to 0.5 with pronounced TADF activity.
近年来，由于有机材料作为高效有机发光二极管（OLED）中的发光体具有潜在应用价值，对表现出热激活延迟荧光（TADF）的有机材料的研究兴趣显著增加。通过选择不同的给电子或吸电子片段对TADF化合物的分子结构进行简单修饰，为调节发射特性和速率提供了很大的可能性。在此，我们鉴于嘧啶环上取代基对其TADF性质的影响，介绍了一系列新型嘧啶 - 咔唑发光体的合成及其光物理表征。我们证明，与通过亚苯基桥连接的取代基相比，直接连接到嘧啶单元的吸电子取代基对降低单重态和三重态之间的能隙（Δ）以实现高效TADF具有更大的影响。在2位用CN、SCH和SOCH官能团修饰嘧啶单元可将发射产率提高至0.5，并具有明显的TADF活性。
