Synthesis And Properties Of Series Squaraine Derivative

Squaraine dyes have been received great attention in theoretical research and practical applications via their excellent photochemical properties and unique structure. A water-soluble squaraine dye had been designed in this paper. Then chitosan or p-aminoazobenzene were combined with cardoxy benzyl of the squaraine, and two squaraine dye derivatives were obtained, structure and performance of them were studied.The synthesis of squaraine was carried out by condensation of squaric acid and the dye intermediate N-p-carboxybenzyl-2,3,3-trimethyl-3H-indoline-5-potassium sulfonate. Then activate the carboxy benzyl of squaraine to generat active ester, which could react with amino on chitosan or p-aminoazobenzene to obtain squaraine dye derivative SQ-CS, SQ-OD. The products were separated and purified by column chromatography.The UV-vis absorption spectra showed that the maximum absoption peak of squaraine dye was 639 nm in methanol, the biggest fluorescence emission wavelength was 650.6 nm, and the stocks displacement value was 11.6 nm; Derivative SQ-CS had two main UV-vis absoption peaks which were 638 nm and 553.5 nm; Derivative SQ-OD had two main UV-vis absoption peaks which were 638 nm and 373 nm; Derivative also had high molar absorption coefficient. The scope of the absorption of squaraine dye was broadened by combining with chitosan or p-aminoazobenzene. With the increase of polarity of the solvent, the maximunu UV-vis absorption wavelength occurred blue-shift, showed negative solvatochromism. The UV-vis absorption spectra also effected by p H. Acid and alkali could damage the internal structure of dye, only neutral condition had higher UV-vis absorption wavelength.Through thermogravimetric found that the decomposition of squaraine was 420℃, the decomposition of derivative SQ-CS was 510℃and the decomposition of derivative SQ-CS was 510℃. This showed that squaraine derivatives had slightly higher thermal stability than squaraine. They also tested the surface morphology by SEM, TEM and AFM. Squaraine and derivative SQ-OD were lamellar irregular arrangement, and derivative SQ-CS was coated a tip of chitosan on squaraine surface, The above materials could be used as photosensitizer which will provide basis for new dye-sensitised solar cells research.