Synthesis, X-ray crystal structure and optical properties of novel 5-(3-aryl-1H-pyrazol-5-yl)-2-(6-methoxy-3-methylbenzofuran-2-yl)-1,3,4-oxadiazole

A series of novel 5-(3-aryl-1H-pyrazol-5-yl)-2-(6-methoxy-3-methylbenzofuran-2-yl)-1,3,4-oxadiazole derivatives has been synthesized from 6-methoxy-3-methylbenzofuran-2-carboxylic acid and ethyl 3-aryl-1H-pyrazole-5-carboxylate. The structures of compounds obtained were determined by IR, 1H NMR and HRMS spectra. Typically, the spatial structure of compound 7e was determined by using X-ray diffraction analysis. UV–vis absorption and fluorescence spectral characteristics of the compounds in dichloromethane and acetonitrile were investigated. The results showed that the absorption maxima of the compounds vary from 321 to 339 nm depending on the substituents in N-1 position of pyrazole moiety and para position of benzene moiety. The maximum emission spectra of compounds in two different solvents were mainly dependent on groups in N-1 position of pyrazole moiety. The intensity of absorption and fluorescence was also correlated with substituents on the aryl ring bonded to pyrazole moiety. In addition, the absorption and emission spectra of these compounds change with increasing solvent polarity.

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► Novel 1,3,4-oxadiazole derivatives were prepared and fully characterized.
► X-ray crystal structure of compound 7e was reported.
► UV–vis absorption and fluorescence spectroscopy of all compounds were measured.
► Influence of solvent on UV–vis absorption and fluorescence spectroscopy was examined.