Synthesis And Properties Of Squaraine Derivative Photosensitizers

Squarylium dyes have been widespread concerned in theoretical research andpractical applications due to their unique structure and excellent photochemical properties.In this paper, three kinds of squaraine dyes were synthesized. By introducing the group ofp-aminoazobenzene and benzylamine in the square ring of squaraines, four kinds ofderivatives of squarylium dyes were obtained, then their spectral and photoelectricproperties were studied.Syntheses of squarylium dyes SQ1,SQ2and SQ3were carried out by condensationof squaric acid and the dye intermediate M1(N-methyl-2,3,3-trimethyl-3H-indoline),M2(N-p-carboxybenzyl-2,3,3-trimethyl-3H-indoline-5-potassium sulfonate),M3(N-ethyl-2,3,3-trimethyl-3H-indoline-5-potassium sulfonate). The squaraine dye drivatives SQ1-OD, SQ2-OD and SQ1-BA, SQ2-BA were obtained by introducing the group ofp-aminoazobenzene and benzylamine in square ring. The products were separated andpurified by column chromatography, their structures were confirmed by HNMR, ESI-MSand IR.The UV-vis absorption spectra showed that the maximum absorption peak ofsquarylium dyes SQ1,SQ2,SQ3were624nm,639nm,634nm in methanol. The maximumabsorption peak of squaraine dye derivatives SQ1-OD, SQ2-OD, SQ1-BA, SQ2-BA were637nm,638nm,643nm,640nm in methanol. In different solvent, maxima UV-visabsorption spectra of all the products occurred blue-shift with the increase of solventpolarity, showing a negative solvatochromism. furthermore, all these dyes had a largemolar extinction coefficient,which was important for them to apply as photosensitizer.Nanocrystalline TiO2films were sensitized with the obtained dyes by impregnationmethod. Dye-sensitized solar cells was also made out, and the photocurrent andphotovoltage were tested.