Studies On Synthesis And Photochromic Properties Of Pyrazolone Derivants In The Solid State

Photochromic material is a new kind of functional material that has the special photochemistry property, and these high functional materials have extensive potential use in optical storage, photoswitch, non-linear optical and holographic anti-counterfeit field, In recent years, the development of photochromic materials has attracted great attention for their potential applications. Although many photochromic compounds have been reported, but compounds are not so much reported that have show good photochromic in the solid state, which makes it a great limit to the development application of this material. Derivatives of pyrazolone could carry on not only extraction and coordination but some also good photochromic reaction in the solid state, and have greater potential use in applications.On the basis of previous research, several series of photochromic compounds though introducing halogen substitutents on benzal of the 4-position of pyrazolone-ring have been synthesized. The photochromic mechanism of these pyrazolone thiosemicarbazone photochromic materials was analyzed and presumed by studying the properties and crystal strutures of the photochromic compounds. The relation between the structure and properties has been obtained.In the first chapter, four new 4-acyl pyrazolone thiosemicarbazones compounds: 1-phenyl -3-methyl-4-(2-chlorobenzal)-5-pyrazolone 4-methylthiosemicarbazone (PM2ClBP-MTSC), 1-phenyl-3-methyl-4-(2-chlorobenzal)-5-pyrazolone 4-ethylthiosemicarbazone(PM2ClBP- ETSC), 1,3-diphenyl-4-(2-chlorobenzal)-5-pyrazolone 4-methylthiosemicarbazone (DP2ClBP -MTSC), 1,3-diphenyl-4-(2-chlorobenzal)-5-pyrazolone 4-ethylthiosemicarbazone (DP2ClBP -ETSC) have been synthesized and characterized by elemental analyses, IR, 1H NMR spectra and single-crystal XRD. DP2ClBP-MTSC shows good reversible photochromic properties. The photochromic properties and photochemical kinetics have been studied by solid-state time-dependent UV-vis absorption spectra and fluorescence spectra under irradiation of 365 nm light. The crystal structure of DP2ClBP-MTSC shows the photo chromism is due to the photoisomerization from the enol form to the keto form. According to the results of structure analyses a hypothesis that photochromic mechanism is due to intra- and intermolecular two steps proton transfer rather than the intermolecular proton transfer only. There exists a thiol form intermediate in photochromic reaction.In the second chapter, two series of 1-phenyl-3-methyl-4-(3,4-dichlorobenzal)-5-pyrazolon- e and 1,3-diphenyl-4-(3,4-dichlorobenzal)-5-pyrazolone 4-thiosemicarbazones have been pr- epared. The structures of 1-phenyl-3-methyl-4-(3,4-dichlorobenzal)-5-pyrazolone 4-thiosemi carbazone (PM3,4ClBP-TSC), 1,3-diphenyl-4-(3,4-dichlorobenzal)-5-pyrazolone 4-methyl thiosemicarbazone (DP3,4ClBP-MTSC) and 1,3-diphenyl-4-(3,4-dichlorobenzal)-5-pyrazolo- ne 4-ethylthiosemicarbazone (DP3,4ClBP-ETSC) were determined by X-ray crystallography, other molecular structures of the derivatives were obtained by the techniques of elemental analyses, IR, and 1H NMR spectra. They all show photochromic properties in the solid state except DP3,4ClBP-MTSC. The photochromic properties have been studied by UV-vis absorption spectra and fluorescence spectra under irradiation of 365 nm light, and the fluorescence contrast was obtained. According to the results of structure analyses a hypothesis that photochromic mechanism is due to intermolecular proton transfer.In the third chapter, two series of 1-phenyl-3-methyl-4-(3-fluorobenzal)-5-pyrazolone and 1,3-diphenyl-4-(3-fluorobenzal)-5-pyrazolone 4-thiosemicarbazones have been prepared. They all have photochromic properties in the solid state. The structure of 1,3-diphenyl-4-(3-fluorobenzal)-5-pyrazolone 4-ethylthiosemicarbazone (DP3FBP-ETSC) was confirmed exactly by X-ray crystallography and analyzed meticulously. The photochromic properties have been studied by UV-vis absorption spectra and Fluorescence spectra under irradiation of 365 nm light, and the fluorescence contrast was obtained. The mechanism was similar to that of the first chapter.