Synthesis, X-ray crystal structure and optical properties research of novel diphenyl sulfone-based bis-pyrazoline derivatives

A series of novel bis-pyrazoline derivatives were synthesized by the reaction of chalcone and (sulfonylbis(3,1-phenylene))bis(hydrazine) in 20–34% yields. The structures of the compounds were determined by IR, 1H NMR, HRMS spectra, and a representative compound 3b was confirmed based on the X-ray crystallographic analysis. Absorption and fluorescence spectra of these compounds in dichloromethane solution were investigated. The results showed that the emission maxima varied from 415 to 444 nm mainly depending on C3 substituents of pyrazoline moiety. The compounds had higher quantum yields, when C3 substituent was an electron-withdrawing p-chlorophenyl group. Moreover, absorption spectra and emission spectra exhibited a blue-shift and a red-shift with increasing the polarity of solvents, respectively. Fluorescent molecules happened to collide with each other and resulted in quench of the fluorescence when the concentration increased over to 10−5 M.