The synthesis, X-ray crystal structure and optical properties of novel 1,3,5-triaryl pyrazoline derivatives

A series of novel 1,3,5-triaryl pyrazoline derivatives has been synthesized by the reaction of chalcone and 3-chloro-6-hydrazinylpyridazine in 47–82% yields. The structures of compounds obtained were determined by IR, 1H NMR and HRMS spectra. Representatively, the spatial structure of compound 3d was determined by using X-ray diffraction analysis. Absorption and fluorescence spectral characteristics of the compounds were investigated in CHCl3 by UV–vis absorption and emission spectra. The results showed that the absorption maxima of the compounds vary from 332 to 342 nm depending on the group bonded to benzene rings. The maximum emission spectra of compounds in CHCl3 are dependent on groups in benzene ring in which a strong electron-donating group in benzene ring such as methoxyl group on C3 position of pyrazoline made the emission wavelength of 3e, 3f and 3g red shifted than that of compounds 3b, 3c and 3d with chlorine group. The intensity of absorption and fluorescence was also correlated with substituent on two aryl rings. In addition, the absorption spectra of these compounds change very little with increasing solvent polarity.