Highly twisted 1,3,4-oxadiazole based hybrid fluorescent organic materials: Synthesis, characterization, density functional theory calculations, and optoelectronic study

Abstract

Heterocyclic compounds based on 1,3,4-oxadiazole (ODA) have attracted considerable attention in the field of pharmacy, drug discovery, and in the field of material sciences. This article reports a series of new highly twisted blue- and green-emitting ODA-based materials 4(a–e) utilizing a simple and efficient synthetic approach, resulting in high yield. The formation of multiple CN bonds unfolds via a simple nucleophilic method that does not need costly metal catalysts. The derivative structures were validated using analytical methods such as ¹H NMR, ¹³C NMR, and high-resolution mass spectrometry (HRMS). Using fluorescence spectroscopy, UV–Vis spectroscopy, and fluorescence lifetime measurements, a thorough investigation was carried out on the photophysical characteristics of the newly synthesized derivatives. A deeper understanding of intramolecular charge transfer was uncovered via solvent-dependent spectroscopy. Specifically, these materials show a large stock shift of up to 153 nm and long fluorescence decay value between 8 and 8.6 ns. Computational methods pinned on density functional theory (DFT) were used to determine the highest occupied molecular orbital–lowest unoccupied molecular orbital energy gaps. The optical band gaps derived from absorption peaks and the band gaps computed by DFT computations are highly correlated. Using cyclic voltammetry study, the compounds' redox potentials were further investigated. These results indicate that the ODAs 4(a–e) are promising organic materials and could play an important role in the field of optoelectronic devices, bioimaging, and photo-redox reactions.