Design, Synthesis And Properties Study Of Unsymmetrical Squaraine Dyes Based On Quinoline, Acridine And Aniline Derivatives

The development of squaraine dyes has experienced45years since they werefirst synthesized and their applications have been extended to various fields. Theintense absorption and emission properties of squaraine dyes in the visible andnear-infrared region are highly suited for applications related to photosensitizationphenomenon. Therefore, squaraine chemistry has become research focus in recentyears. The reports of squaraines in the solar cells related to photosensitizationphenomenon are increasing year by year, which exhibits good application prospect inthis field. In the solar cells the unsymmetrical squaraine dyes were mostly reportedcompared to other kind of squaraine dyes and relative theories were also accepted. Inthis thesis, five novel unsymmetrical squaraine dyes, not been reported so far, havebeen synthesized and characterized by IR,1H NMR, MS, HRMS and elementalanalysis. Their potential properties have been studied systematically by means ofabsorption spectra, cyclic voltammetry experiments and theoretical calculations.The half-peak widths of typical symmetrical squaraine dyes substituted byaniline and quinoline moieties are usually narrow, which restricts their absorption inwider band from sunlight. Whereas, the half-peak widths of these unsymmetricalsquaraine dyes are generally wide. The absorption properties of these new dyes willbe altered when introducing the aniline and quinoline moieties to a squaraine dye.The new dyes exhibit obvious wide absorption band when the two parts wereintroduced to the unsymmetrical squaraine dyes. The half-peak widths are in therange of86~96nm, which enhances dramatically compared to the symmetricalsquaraine dyes with the same substituents. The solvent effect experiments showedthat the new dyes displayed negative solvatochromism, that is, the maximumabsorptions of these new dyes are hypsochromic shift with the solvent polarityincreasing. The half-peak width of symmetrical squaraine dyes based on acridinederivative is also wide. The absorption band became further wider with the half-peakwidth135nm when the half moiety of the symmetrical squaraine dye was replacedby aniline moiety. The protonation of these new dyes was investigated and the experiment resultsimplied that the protonation only occurred on the nitrogen atom of the side chain ofthe squaraines. The absorption bands were blue-shifted with the acid concentrationincreasing. In addition, the solvent would affect the protonation behavior of thesenew dyes, which exhibited clearer protonation behavior in the polar protophobicsolvent than in the polar protophilic solvent. The photostability of these new dyeshad solvent effect in the different solvents. Generally, the new dyes had goodphotostability in the protic solvent. The energy levels of these new dyes werecalculated by absorption spectra and cyclic voltammetry experiments indichloromethane and theoretical simulation. The results showed that the energy levelof these dyes matched the common acceptor materials well, which indicated thatthese unsymmetrical squaraine dyes have potential application prospect in the solarcells.