Study On The Synthesis, Crystal Structure And Properties Of Photochromic Compounds About Pyrazolone Thiosemicarbazone

Organic photochromic compounds and their chemistry have been developed and studied comprehensively for over a hundred years. For example, spirocompounds, fulgides, spirooxazines have been much studied due to their potential wide application in information recording and processing, variable transmitting materials and molecular switching devices. There is certain interest in the photochromism of transition metal and rare earth complexes which have photochromic ligands such as spiropyrans and spirooxazines. But little attention is paid to those thiosemicarbazones(TSCs) photochromic compounds which contain pyrozolone ring.On the basis of the work of previous graduate students, a series of new photochromic compounds and their relevant derivatives containing pyrozolone-ring have been synthesized. The photochromic mechanism was analyzed and presumed by studying the properties and crystal struture of the photochromic compounds. The relation between the structure and properties has been obtained.In the first part, four new photochromic compounds, l-Phenyl-3-methyl-4-(4-bromobenzal)pyrazol-5-one N(4)-methyl-3-thiosemi-carbazone(PM4BrBP-MTSC), 1-Phenyl-3-methyl-4-(4-bromobenzal)pyrazol-5-one thiosemicarbazone(PM4BrBP-TSC), l-Phenyl-3-methyl-4-(2-chlorobenzal) pyrazol-5-one N(4)-methyl-3-thiosemicarbazone (PM2C1BP-MTSC), 1,3-phenyl-4-benzoformyl-pyrazol-5-one N(4)-methyl-3-thiosemi-carbazone(PPBP-MTSC) have been synthesized and characterized by elemental analyses, UV spectra, single-crystal XRD. The photochromic properties and photochemical kinetics of these compounds have been studiedby solid Time-dependent UV-vis absorption spectra under irradiation of 365nm light. The crystal structure of colorless product of PM4BrBP-TSC and yellow product of PM4BrBP-MTSC shows the photochromism is due to the photoisomerization only from one keto form to another keto form. According to the results of structure analyses, the mechanism of conformation change for photochromism is proposed.In the second part, l-phenyl-3-methyl-4-propropionyl-5-pyrazol-one(PMPP) and l-phenyl-3-methyl-4-phenylacet-5-pyrazolone(PMPaP) including their derivatives have been prepared. The conformation of l-phenyl-3-methyl-4-propropionyl-pyrazol-5-one semicarbazone(PMPP-SC) and l-phenyl-3-methyl-4-phenylacet-pyrazol-5-one semicarbazone(PMPaP-SC) were determined by X-ray crystallography, other molecular structure of the derivatives were obtained by the techniques of elemental analyses, IR and 1HNMR. We have envisioned the reason of non-photochromism for these compounds by analyzing their structure, and then acquired the conclusion that, if the 4-position of pyrazolone-ring is the conjugate group of electron contributing, for example, phenyl and other substituted phenyl, the compounds synthesized possess the properties of photochromism, to the contrary, there is no photochromism. In the other words, their process of photochromism have been completed in solution, and the structures of compounds participated from solution are stable, and their conformation cannot be changed, even though the energy(e.g. Uv-visible light) were added. So, the photochromism cannot be observed.In the third part, a series of novel heterocyclic compounds PMCP-MTSC [l-phenyl-3-methyl-4-(6-hydro-4-methylamino-5-sulfo-2,3-pyrazine)-pyrazole-5-one], PMCP-PTSC, PPCP-TSC, PPCP-MTSC, PPCP-PTSC, PPCP-SHN have been synthesized and characterized by elemental analyses, IR spectra, 1H NMR spectra and single-crystal XRD. Three structures of them were confirmed exactly by X-ray crystallography and analyzed meticulously. The mechanism of reaction was discussed preliminarily and the reason of non-photochromism is obtained by contrast the structure of PMCP-TSC.