Experimental and theoretical comparative studies on two 2-pyrazoline derivatives

Two 2-pyrazoline derivatives of 1-phenyl-3-(4-methylphenyl)-5-phenyl-2-pyrazoline (1) and 1-phenyl-3-(4-methylphenyl)-5-(2,4-dichlorophenyl)-2-pyrazoline (2) have been synthesized and characterized by elemental analysis, IR, UV–vis and fluorescence spectroscopy. The crystal structure of 2 has been determined by X-ray single crystal diffraction. For the two compounds, density functional theory (DFT) calculations of the structures and natural population atomic charge analysis have been performed at B3LYP/6-311G** level of theory. By using TD-DFT method, electron spectra of 1 and 2 have been predicted, which suggests the B3LYP/6-311G** method can approximately simulate the electron spectra for the system presented here. Comparative studies on 1 and 2 indicate that the change of substituent in 5-phenyl ring of pyrazoline ring influences the peak location and intensity in electronic and fluorescence spectra.