Synthesis, structure and properties of a novel kind of photochromic compound containing a pyrazolone-ring

Two new organic photochromic compounds containing pyrazolone-ring as photoc hromic functional unit: 1-phenyl-3-methyl-4-benzoylpyrazol-5-one thiosemica rbazone (1A) and 1-phenyl-3-methyl-4-benzoylpyrazol-5-one S-methylthiosemic arbazone (2A), and some analogous non-photochromic derivatives were synthes ized and characterized by elemental analysis, MS, IR Spectra, NMR spectra. The photochromic properties and photocolored kinetics of 1A and 2A were stu died by powder-UV reflectance spectra under irradiation of 293 nm light. Th e crystal structure analysis of photocolored product of 1A showed the photo chromic phenomenon was due to the photoisomerization from enol form to keto form. With the addition of the analysis of IR spectra, an intermolecular p roton transfer mechanism of the photochemical process was proposed. (C) 200 0 Elsevier Science S.A. All rights reserved.