Synthesis, Photochromic Properities And Molecular Logic Switches Of Schiff Base Containing Pyrazolone

Schiff bases compounds have elicited intense interest for their outstanding tautomers and the wide applications in photochromism, light storage, organic photoelectric functional materials and functional information materials.On the basis of previous work in our laboratory, several novel thiosemicarbazones and phylsemicarbazone compounds containing pyrazolone-ring which was bearing different electron–donating or electron–withdrawing substituting have been synthesized. The photochromic mechanism of these photochromic compounds was analyzed and presumed by studying the photochromic properties and crystal strutures. The relation between the structure and properties has been obtained. In additional, the spectral properties of the compounds were investigated detailedly by the UV-Vis absorption spectra in methanol solutions with different pH. By encoding logic digits, we obtained one INHIBIT logic function gate.In the first chapter, six new 4-acyl pyrazolone phenylsemicarbazone have been prepared. The structure of three photochromic compounds characterized by elemental analyses, IR, 1H NMR spectra. The photochromic properties and photochemical kinetics have been studied by solid-state time-dependent UV-vis absorption spectra and fluorescence spectra under the irradiation of 365 nm light. We found that two compounds DP3BrBP-PSC and DP4IBP-PSC exhibit good reversibility and fatigue, which can be used as the light-heat controlled switch and fluorescent switch. According to the results of structure analyses, an intramolecular proton transfer or intermolecular double-proton transfer mechanism was proposed.In the second chapter, fifteen new pyrazolone thiosemicarbazones compounds bearing different electron–donating or electron–withdrawing substituent groups have been synthesized and characterized by element analyse, IR, 1H NMR spectra, theoretical calculation and X-ray single crystal diffraction. In solid state, they exhibit photochromic properties under UV light irradiation. Nine of them have shown reversible photochromic properties. Based on the crystal structure, solid IR spectra and theoretical calculation, we proposed two kinds of the photochromic mechanisms: the intra- and intermolecular double-proton transfer or intermolecular proton transfer from enol–form to keto–form in the solid state. The experimental results also demonstrate that the effect of the 3-position groups of pyrazolone ring on photochromic properties is unconspicuous. The electron–withdrawing substituents on pyrazolone 4-position can shift the absorption maxima to a longer wavelength of the keto products.In the third chapter, the spectral properties of the eleven reversible photochromic compounds were investigated detailedly by the UV-Vis absorption spectra in methanol solutions with different pH, a pH switch can be obtained. By encoding logic digits in inputs (OH-, H+, Zn2+) and outputs (absorption) in solution, an INH logic molecular circuit by combining a NOT and an AND gate can be achieved.