Synthesis And Photochromic Properties Of Pyrazolones Containing Thiophene Ring

Photochromic materials have attracted considerable attention owing to their potential applications in photoactive devices, such as optical memories and switches, ophthalmic lenses, nonlinear-optical materials, smart windows, etc. Pyrazolones as a new kind of organic photochromism, which exhibit reversible photochromic properties in the solid state. Solid-state photochromic materials are indispensable for practical applications. Therefore, further studies on pyrazolone derivatives will extend the development and application of organic photochromic materials.On the basis of previous research, series pyrazolone phenylsemicarbazones containing a thiophene ring have been synthesized by introducing an electron-rich thiophene ring on the3-position of the pyrazolone ring. And their photochromic properties, chemical kinetics and structures have been analyzed. The relation between structures and properties has been obtained.In the first chapter, nine novel compounds [1-phenyl-3-(2-thiophenyl)-4-substituted benzal-5-hydroxypyrazole phenylsemicarbazone] have been synthesized. The composition and structures of these compounds were characterized by1H NMR, MS 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 under irradiation of365nm light and heat. Compared with the reversibility and thermal bleaching of the previously reported compounds, the as-synthersized compounds show better fatigue resistance and faster thermal bleaching reaction, which should be attributed to the electron-rich2-thiophenyl group at the3-position on the pyrazolone-ring. Furthermore, their UV-Vis absorption spectra red-shift with the increase of the electron withdrawing ability of groups at the para-position of the benzylidene at the4-position of the pyrazolone ring. And the UV-Vis spectra of the compound1-phenyl-3-(2-thiophenyl)-4-(4-nitrobenzal)-5-hydroxypyrazole4-phenylsemicarbazone (P2Th4NO2BP-PSC) red-shifts to the Visible light range, which takes on photochromic behavior upon the visible light irradiation due to the strong electron withdrawing of nitro group.In the second chapter, a novel pyrazolone phenylsemicarbazone containing two thiophene rings,1-phenyl-3-(2-thiophenyl)-4-(2-thenylidene)-5-hydroxypyrazole4-phenylsemicarbazone [PD(2Th)P-PSC], was synthesized. The compound exhibits solid-state photochromic properties, thermally enhanced phenomenon and automatic "window curtain" performance in solid state. Its photochromic properties, structure, thermally enhanced kinetics and the activation energy of the thermal enhancement were characterized. And a new photoactive PD(2-Th)P-PSC/PS composite film was prepared as a new potential smart window curtain.