Aromatic systems with two and three pyridine-2,6-dicarbazolyl-3,5-dicarbonitrile fragments as electron-transporting organic semiconductors exhibiting long-lived emissions

Karolis Leitonas; Brigita Vigante; Dmytro Volyniuk; Audrius Bucinskas; Pavels Dimitrijevs; Sindija Lapcinska; Pavel Arsenyan; Juozas Vidas Grazulevicius

doi:10.3762/bjoc.19.139

Aromatic systems with two and three pyridine-2,6-dicarbazolyl-3,5-dicarbonitrile fragments as electron-transporting organic semiconductors exhibiting long-lived emissions

Beilstein J Org Chem. 2023 Dec 12:19:1867-1880. doi: 10.3762/bjoc.19.139. eCollection 2023.

Authors

Karolis Leitonas¹, Brigita Vigante², Dmytro Volyniuk¹, Audrius Bucinskas¹, Pavels Dimitrijevs², Sindija Lapcinska², Pavel Arsenyan², Juozas Vidas Grazulevicius¹

Affiliations

¹ Department of Polymer Chemistry and Technology, Kaunas University of Technology, Radvilenu pl. 19, LT-50254, Kaunas, Lithuania.
² Latvian Institute of Organic Synthesis, Aizkraukles 21, LV-1006, Riga, Latvia.

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.

Keywords: charge transport; intramolecular charge transfer; photophysical properties; pyridine-3,5-dicarbonitrile.

Grants and funding

This work was supported by the project of scientific co-operation program between Latvia, Lithuania, and Taiwan, "Synthesis and study of deep-blue TTF fluorescent emitters to exceed theoretical OLED external quantum efficiency reaching 15%" (grant LV-LT-TW/2023) and Research Council of Lithuania (LMTLT), agreement no. S-LLT-22-4. This project has also received funding from the Research Council of Lithuania (LMTLT), agreement No S-MIP-22-78.