Synthesis and spectroscopic study on photochromism of a new thiosemicarbazone compound containing pyrazolone

A new photochromic compound 1,3-diphenyl-4-(4′-fluro)benzal-5-pyrazolone-4-ethyl thiosemicarbazone (DP4FBP-ETSC) was synthesized by direct condensation of 1,3-diphenyl-5-pyrazolone with N(4)–ethyl thiosemicarbazide. The product was characterized by elemental analysis, IR and 1H NMR spectra. The photochromic properties of the compound were studied using time-dependent fluorescence emission spectra, the UV–vis reflection spectra in the solid state and the UV–vis absorption spectroscopy in liquid. The reaction rate constant of compound was also analyzed. The results show that DP4FBP-ETSC can perform photochromism.