Investigation On Synthesis, Crystallography And Optical Properties Of Carboxyl-containing Negative Photochromic Spiropyrans

Spiropyran compounds and their derivatives have got extensive attention since theirdiscovery due to their special photochromic optical properties. However, the mostprevious reported researches focused mainly on the spiropyran compounds in solution,and rarely in solid materials. Tautomerism of spiropyran makes it difficult to obtainsingle crystal, and seriously hindered the research on the solid-state structure and theluminescence mechanism of spiropyrans. Thus, the study of crystallography ofspiropyrans is of great scientific and practical importance. In this research, focus hasbeen placed on the study of carboxyl-containing spiropyrans, and the main objectivewas to prepare some novel photochromic materials, and to find the crystallographyfeature of this kind tautomeric system by theoretical analysis and experimentalmethod.The first part of this dissertation provided a detailed introduction on the basicoverview of the photochromic compounds, spiropyran compounds, photochromicmechanism, as well as their application and crystallography, followed by the researchstrategy and plan proposed in the end of this chapter.Chapter two presents the design and synthesis of a series of carboxyl-containingspiropyran compounds:1’,3’,3’-trimethylspiro[chromene-2,2’-indoline]-5’-carboxylicacid (CSP),8-methoxy-1’,3’,3’-trimethylspiro[chromene-2,2’-indoline]-5’-carboxylicacid (o-CSP),7-methoxy-1’,3’,3’-trimethylspiro[chromene-2,2’-indoline]-5’-carboxylic acid (m-CSP),6-methoxy-1’,3’,3’-trimethylspiro[chromene-2,2’-indoline]-5’-carboxylic acid (p-CSP),5-methoxy-1’,3’,3’-trimethylspiro[chromene-2,2’-indoline]-5’-carboxylic acid (f-CSP). All of these compounds were fully characterizedby1H NMR spectroscopy, IR spectroscopy, elemental analysis and high resolutionmass spectrometry, et al.In order to study the crystallography of spiropyran compounds, Chapter threedescribed the cultivation of single crystal for the synthesized spiropyran compounds.The computer-aided calculation has been carried out to understand the preliminarycrystallography feature. The well single crystal of the following three compoundshave been successfully obtained by recrystallization:1’,3’,3’-trimethylspiro[chromene-2,2’-indoline]-5’-carboxylic acid,8-methoxy-1’,3’,3’-trimethyl-spiro[chromene-2,2’-indoline]-5’-carboxylic acid, and6-methoxy-1’,3’,3’-trime- thylspiro[chromene-2,2’-indoline]-5’-carboxylic acid. Their single crystal structureshave been characterized by X-ray crystallography method. At the same time, thestructures and properties of open and closed forms of decades spiropyran compound,including these synthesized here and the representative ones reported in literature,were systematical analyzed by Density functional theory (DFT). The crystallization ofspiropyrans was found to be related with the difference of the dipole moment betweenthe open-loop and closed-loop. It laid a theoretical basis for further study on thecrystallization of spiropyran compounds.Finally, the optical properties of the spiropyrans were studied in depth in Chapterfour. These compounds show strong blue luminescence with the maximum emissionwavelength at about400nm. In addition, the negative photochromic properties of thecompounds were explored by UV absorption spectroscopy, and could be used inanti-counterfeiting technology. The dynamics change and the fatigue resistance of thecompounds between colorless and colored conformation have also been investigated.