Four unsymmetrical squaraine dyes 7a～7d based on quinoline and aniline derivatives have been synthesized and characterized by ¹H NMR, MS and elemental analysis. The synthetic conditions of the intermediates 3a～3c were investigated. As the electron withdrawing ability of the 6-position substituent of quinoline increased, the reactivity of nucleophilic substitution decreased, so the harsher condition was needed. The synthetic methods of the unsymmetrical dyes were explored. The results showed that the inoculation sequence of the precursor of unsymmetrical squaraine dyes was the key to the completion of the reaction successfully. The absorption spectra and photostability of the unsymmetrical squaraines were studied systematically. The results revealed that the half-peak width for the absorption band of the dyes was wide and the absorption spectra exhibited blue-shift with the increase of solvent polarity, showing a negative solvatochromism. The absorption decay under irra-diation demonstrated that the photostabilities of all the four dyes were high and their photostabilities en-hanced further as the electron withdrawing ability of the 6-position substituent of quinoline moiety in-creased. In addition, the length of the alkyl chain at the nitrogen of the aniline moiety also influenced the photostabilities of the dyes.

Key words: unsymmetrical squaraine, synthesis, photostability, bulk-heterojunction