Abstract

The pyridine-3,5-dicarbonitrile moiety has gained significant attention in the field of materials chemistry, particularly in the development of heavy-metal-free pure organic light-emitting diodes (OLEDs). Extensive research on organic compounds exhibiting thermally activated delayed fluorescence (TADF) has led to numerous patents and research articles. This study focuses on the synthesis and investigation of the semiconducting properties of polyaromatic π-systems containing two and three fragments of pyridine-2,6-dicarbazolyl-3,5-dicarbonitrile. The compounds are synthesized by Sonogashira coupling reactions and characterized by steady-state and time-resolved luminescence spectroscopy. The compounds show efficient intramolecular charge transfer (ICT) from the donor to the acceptor. The photoluminescence (PL) spectra of the solutions of the compounds showed non-structured emission peaks in the visible region, which are attributed to ICT emission. The PL intensities of the solutions of the compounds are enhanced after deoxygenation, which is indicative of TADF. The photoluminescence quantum yields and TADF properties of the compounds are sensitive to the medium. Cyclic voltammetry measurements indicate good hole-blocking and electron-injecting properties due to their high ionization potentials. Photoelectron spectroscopy and time-of-flight measurements reveal good electron-transporting properties for one of the compounds. In general, polyaromatic π-systems with pyridine-3,5-dicarbonitrile fragments demonstrate promising potential for use in organic electronic devices, such as OLEDs.

Beilstein J. Org. Chem. 2023, 19, 1867–1880. doi:10.3762/bjoc.19.139

摘要

吡啶-3,5-二甲腈部分在材料化学领域引起了极大的关注，特别是在不含重金属的纯有机发光二极管（OLED）的开发中。对具有热激活延迟荧光 (TADF) 的有机化合物的广泛研究已经产生了大量专利和研究文章。本研究重点是含有两个和三个吡啶-2,6-二咔唑基-3,5-二甲腈片段的聚芳族π-系统的合成和半导体性能研究。这些化合物通过 Sonogashira 偶联反应合成，并通过稳态和时间分辨发光光谱进行表征。这些化合物表现出从供体到受体的有效分子内电荷转移（ICT）。化合物溶液的光致发光（PL）光谱在可见光区域显示出非结构发射峰，这归因于ICT发射。化合物溶液的PL强度在脱氧后增强，这表明TADF。化合物的光致发光量子产率和TADF性质对介质敏感。循环伏安法测量表明由于其高电离势而具有良好的空穴阻挡和电子注入特性。光电子能谱和飞行时间测量揭示了其中一种化合物具有良好的电子传输特性。一般来说，具有吡啶-3,5-二甲腈片段的聚芳族π-系统在有机电子器件（例如OLED）中表现出良好的应用潜力。

贝尔斯坦 J. 组织。化学。 2023, 19, 1867–1880。doi:10.3762/bjoc.19.139