Synthesis, Structure And Photochromism Of 4-acyl Pyrazolone Derivants In Solid State

Organic photochromic compounds are of great interest due to their applications in optical information recording, nonlinear optical apparatus, civilian goods (eg. anti-counterfeiting, textile, ophthalmic lenses) and these materials also have potential applications in molecule wire, biological probes, biological supramolecules and molecular switching devices. Although many photochromic compounds have been so far reported, compounds with photochromic properties in the crystalline phase are rare.On the basis of the previous work in our laboratory, several new thiosemicarbazones compounds containing pyrazolone-ring have been synthesized. The photochromic mechanism was discussed and presumed by studying their properties and crystal structures. The relationship between the structure and properties has been discussed. There are four parts in this thesis.In the first part, five new photochromic compounds have been synthesized and characterized by elemental analyses, IR, 1H NMR spectra. The photochromic properties have been studied by UV-Vis absorption spectra. The pseudo-first reaction rate constants of the three compounds 1-phenyl-3-phenmethyl-4-(4-bromo) benzal-5-pyrazolone thiosemicarbaz1(PPe4BrBP-TSC), 1,3-diphenyl-4-(4-bromo) benzal-5-pyrazolone thiosemicarbazone(DP4BrBP-TSC), 1-phenyl-3-methyl-4- (4-bromo)benzal-5-pyrazolone thiosemicarbaz1(PM4BrBP-TSC) are obtained: k1 (PM4BrBP-TSC)< k1 (DP4BrBP-TSC) < k1 (PPe4BrBP-TSC). The rate of the photoisomerism is related to the substituent group on the pyrazolone. The crystal structures of 1,3- diphenyl-4-(4-methyl)benzal-5-pyrazolone thiosemicarbazone (DP4MBP-TSC) and DP4BrBP-TSC show the photochromism due to their photoisomerization from enol form to keto form. According to the results of structure analyses, there is a proton transfer through the two intermolecular hydrogen bonds.In the second part, the configurations of the six new thiosemicarbazones compounds containing pyrazolone-ring were determined by elemental analyses, IR, 1H NMR spectra and X-ray crystallography. 1-phenyl-3-methyl-4-(3-chloro)benzal -5-pyrazolone methylthiosemicarbazone (PM3ClBP-MTSC) is a reversible photochromic compound. The photochemical property of PM3ClBP-MTSC has been studied by UV-vis absorption spectra. Moreover, the possible mechanism of the reversible photochromism is discussed by the intermolecular hydrogen bond N2-H…O.In the third part, two novel compounds 1-phenyl-3-methyl-4-(3-chloro)benzal -5-pyrazolone ethylthiosemicarbazone (PM3ClBP-ETSC) and 1,3-diphenyl-4-(4- bromo) benzal-5-pyrazolone ethyl-thiosemicarbazone(DP4BrBP-ETSC) have been synthesized and their structures were confirmed exactly by X-ray crystallography and analyzed meticulously. The compound DP4BrBP-ETSC synthesized has no photochromism in solid state. In the other words, the process of photochromism has been completed in solution, and the structure of compound precipitated from solution is stable, and the conformation cannot be changed, even though the energy (e.g. UV-visible light) is added. So, the photochromism cannot be observed.In the fourth part, the molecular structure of 1-phenyl-3-methyl-4-benzal- 5-pyrazol-one butylthiosemicarbazone (PMBP-BTSC) was obtained by X-ray crystallography and confirmed by the techniques of elemental analyses, IR, 1H NMR spectra. 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.