Synthesis, Structures And Solid-state Photochromic Properities Of Pyrazolone Derivatives

Schiff base compounds have attracted considerable interest because of their promising applications in optical storage media, molecular switching devices, molecular sensors and non-linear optical devices,etc.Two series of pyrazolone thiosemicarbazones and pyrazolone phenylsemicarbazones containing furoyl/4-fluorophenyl/phenyl substitute group at 3- position on pyrazolone-ring have been synthesized by the designing of molecules and the modification of strctures. To get a deeper insight to analyse their the photochromic properties, crystal structures and photochromic mechanism, the effect of substitute groups at the 3- or 4-position on the pyrazolone-ring, volume of substituent groups at 4-position of thiosemicarbazone and S & O atom at the side chain on photochromic properties were detailedly studied. These results are useful for the design and synthesis of novel pyrazolone derivatives with good photochromic properties in the solid state.In the first chapter, thirteen new 1-phenyl-3-furoyl/4-fluorophenyl-4-substituted phenyl -5-pyrazolone thiosemicarbazones have been synthesized. The composition and structures of these photochromic compounds were characterized by elemental analyses, IR, 1H NMR spectra and X-ray single crystal diffraction. The photochromic properties and photochemical kinetics have been studied by solid-state UV-vis absorption spectra and fluorescence emission spectra. We found that two compounds P4FP3ClBP-MTSC and P4FP3BrBP-MTSC show reversible photochromic properties. Based on the crystal structure, IR spectra and theoretical calculation, we proposed two kinds of the photochromic mechanism: the intermolecular proton transfer and intermolecular double proton transfer from enol-form to keto-form in the solid state.In the second chapter, nine new 1-phenyl-3- phenyl/furoyl /4-fluorophenyl-4-substituted phenyl-5-pyrazolone phenylsemicarbazones have been synthesized. In solid state, they exhibit excellent photochromic properties under UV light irradiation except for PαF3ClBP-PSC and PαF4ClBP-PSC, seven of them show good reversible photochromic properties and highly fatigue resistant, which have potential application in light-heat controlled switch and fluorescent switch.