Crystal structure and spectroscopic study on photochromism of 1-phenyl-3-methyl-4-benzal-5-pyrazolone 4-ethylthiosemicarbazone

The crystal structure of the title compound 1-phenyl-3-methyl-4-benzal-5-pyrazolone 4-ethyl thiosemicarbazone (PMBP-ETSC), as determined by X-ray analysis, shows that the pyrazolone moiety stabilizes in the keto form and the molecule is found to be in threedimensional arrangement in the unit cell linked by intermolecular hydrogen bonds. The important bands in IR spectra, as well as the main signals of the 1H NMR spectra are assigned. Meanwhile, the steady state, time-dependent fluorescence emission spectroscopy, the powder UV–Vis reflection spectroscopy of the solid product and theoretical chemistry calculations of reaction rate constant are also studied, the results of which show that PMBP-ETSC can perform photochromism. q 2004 Elsevier B.V. All rights reserved