Crystal structure and photoisomerism of 1-phenyl-3-methyl-4-benzal-5-pyrazolone 4-butylthiosemicarbazone in solid state

The structure of 1-phenyl-3-methyl-4-benzal-5-pyrazolone 4-butylthiosemicarbazone (PMBP-BTSC) was confirmed by1H NMR, IR, elemental analyses, and X-ray crystallographic analysis. The photoisomerization of PMBP-BTSC in solid state was studied in the condition of UV-Vis irradiation, and the mechanism of the photoisomerization was interpreted by double proton transfer. Moreover, the effect of the alkyl chain length in the side chain of a series of 4-acyl pyrazolone derivatives on the photochemical properties was discussed.