The search for new fluorescent dyes for the creation of organic light-emitting diodes continues at the ZIOC

At the moment, π-conjugated organic molecules have attracted much attention from scientists due to their ability to optimize light absorption, light emission, charge carrier mobility, conductivity, and other physical properties. Various combinations of electron-donating (D) and electron-withdrawing (A) groups, linked either directly or preferably through π-conjugated bridges (π), have been used in organic chromophores to tune band gap levels and optoelectronic properties. The selection of donor and acceptor fragments is fundamentally important for achieving the best characteristics of organic dyes. The role of acceptors is to fine-tune the levels of boundary orbitals — the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), in the appearance of a difference between these energies and, as a result, the absorption spectra of materials based on these molecules. The choice of an acceptor is important for ensuring high properties of materials based on them both in individual molecules and in polymers. Recently, scientists from the Laboratory of Polysulfur-Nitrogen Heterocycles of the ZIOC have studied Suzuki and Stille cross-coupling reactions for a new acceptor building block 4,8-dibromobenzo[1,2-d:4,5-d']bis([1,2,3 ]thiadiazole). In order to create highly efficient materials for OLEDs, both mono- and bis-coupling products have been obtained. In order to reduce the number of steps in the preparation of these products and avoid the use of toxic tin or organoboron compounds, it was necessary to use direct CH activation reactions of benzo[1,2-d:4,5-d']bis([1,2, 3]thiadiazole).

In one of their recent studies, in order to obtain new fluorescent dyes, scientists from the Laboratory of Polysulfur-Nitrogen Heterocycles of the ZIOC for the first time studied in detail palladium-catalyzed reactions of direct CH activation of benzo[1,2-d:4,5-d']bis([1 ,2,3]thiadiazole) and its 4,8-dibromo derivative. Optimal conditions were found for the selective introduction of various thiophene and aryl derivatives to obtain products as mono- and bis-couplings. It was shown that the synthesis of final compounds from benzo[1,2-d:4,5-d']bis([1,2,3]thiadiazole) was a more efficient method compared to reactions from 4,8-dibromobenzo[1, 2-d:4,5-d']bis([1,2,3]thiadiazole. In addition, for the first time the applicability of the oxidative С-Н activation reaction for benzo[1,2-d:4,5-d' ]bis([1,2,3]thiadiazole) was shown. It was found that the use of silver oxide in dimethyl sulfoxide as an oxidizing agent made it possible to obtain thiophene derivatives of benzo[1,2-d:4,5-d']bis([1,2 ,3]thiadiazole) of various structure. The resulting substances can be considered as starting compounds for creating components of organic light emitting diodes (OLEDs).

Source:

Timofey N. Chmovzh, Timofey A. Kudryashev, Daria A. Alekhina, Oleg A. Rakitin Palladium-Catalyzed Direct (Het)arylation Reactions of Benzo[1,2-d:4,5-d′]bis([1,2,3]thiadiazole and 4,8-Dibromobenzo[1,2-d:4,5-d′]bis([1,2,3]thiadiazole) // Molecules 2023, 28, 3977. DOI: 10.3390/molecules28093977.