The synthesis, characterization and optical properties of novel, substituted, pyrazoly 1,3,4-oxadiazole derivatives

A series of novel substituted pyrazoly 1,3,4-oxadiazole derivatives were synthesized by the reaction of substituted pyrazole-5-carbohydrazide with substituted benzoic acid in the presence of phosphorus oxychloride. The compounds were characterised using IR, 1H NMR and HRMS and X-ray diffraction analysis. The absorption and fluorescence characteristics of the compounds were investigated in dichloromethane. The compounds displayed similar absorption, ranging from 267 to 281 nm with a strong absorption band occurring at ∼275 nm. Correlation of the absorption spectra and fluorescence characteristics of the pyrazoly 1,3,4-oxadiazole derivatives with substituent effects on the benzene rings, revealed that a methoxy and a bromine group attached to the benzene ring markedly influenced maximum emission.