Theoretical Study Of Photochromic Compounds About Schiff Base Containing Pyrazolone

As a new type of functional material, organic photochromic materials have potential applications in optical computer, information storage, light-driven information display etc. Therefore, design and development the organic photochromic materials with excellent properties are of very important significance. A deeper insight into the microstructure of the organic photochromic materials, making clear the photochromic process and mechanism, and establishing the structure-activity relationship of materials will be of great theoretical significance in guiding the design and synthesis of photochromic compounds with excellent properties. During the past twenty years, our laboratory has synthesized a series of pyrazolone photochromic compounds though molecular design and structure modification. And the experiment helps us figure out the composition and structure of those compounds, investigate the photochromic behavior and reaction mechanism, and summarize the rules of the substitution effect on the structure, properties and structure-activity relationship of the compounds. Meanwhile, with the compounds as the ligand, we built a series of the rare-earth and transition metal complexes, but the photochromic mechanism and the structure-activity relationship need further exploration. On the basis of previous experimental and theoretical works, this study explores the photochromic mechanism of three typical photochromic compounds, the effect of halogen substituted on the structure and reactivity of the compound and the coordinated property of the isomers from theoretical point of view. The research content mainly includes the following three parts.Firstly, theoretical studies are conducted on the photochromic mechanism of1,3-diphenyl-4-(4-chloro/bromo)benzal-5-pyrazoloneN(4)-phenyl semicarbazone,1-phenyl-3-methyl-4-(6-hydro-4-amino-5-sulfo-2.3-pyrazine)-pyrazole-5-one, and salicylaldehyde thiosemicarbazone. For the enol and keto tautomer of the three compounds, the structure parameters, the stability and the charge distribution, as well as the reactivity were respectively analyzed and the rationality of photochromic mechanism was proposed and verified. At the same time, the calculated results of the route between transition state and the equilibrium structures of the three compounds are applied to speculate the reaction path.It also studies the effect of halogen substituent in different positions of4-acyl benzene on the structure, stability and reactivity of1.3-diphenyl-4-benzal-5-pyrazolone methylthiosemicarbazone (DPBP-MTSC). The calculated results indicate that the existence of the solvent molecular in crystal structure will directly determine the spatial configuration and the photochemical mechanism of the compounds. Furthermore, the reactivity of these isomers is enhanced when the hydrogen in4-acyl benzene is stituented by halogen.The third part mainly focuses on the coordinated property of N-(1,3-diphenyl-4-acetyl-pyrazolone-5)-salicylidene hydrazone (DPAP-SAH). Through analysis the stability, frontier orbitals and reactivity of the four isomers. it is found that the coordination configuration of DPAP-SAH is different from the isomer which was previously proposed. In addition, the crystal configuration of DPAP-SAH is not directly involved in the coordination reaction because of lack of active site in the molecular even though it has the strongest stability and prone to tautomer reaction.