Symmetrical and non-symmetrical 2,5-diaryl-1,3,4-oxadiazoles: synthesis and photophysical properties

Abstract

We report herein the synthesis of 2,5-diaryl-1,3,4-oxadiazoles containing both electron-donating and withdrawing substituents as well as bis- and tris-2,5-disubstituted-1,3,4-oxadiazoles containing electron-donating substituents. The photophysical properties of the synthesized compounds were studied using UV–Vis and fluorescence spectroscopy. The aryl substitution pattern was found to have a marked impact on both luminescence efficiency and other photophysical properties. An increase in the number of electron-donating groups and/or the number of heterocyclic rings provided a red shift of the emission maxima, as well as an increase of the Stokes shifts. The same effect was observed for mono-1,3,4-oxadiazoles containing push–pull substituents on the aryl rings.