Absorption spectra, aggregation and photofading behaviour of near-infrared absorbing squarylium dyes containing perimidine moiety

Representatives of a new class of squarylium dyes containing a perimidine moiety have been synthesized and characterized. Almost all of these dyes absorbed near infrared light over 800 nm. The light absorption characteristics of these dyes are well accounted for with the PPP-MO calculation. The photostability properties of the dyes were also investigated when hydroperinidine containing quinoline moiety was introduced, the photochemical stability being better than that of dihydroperimidine moiety. The aggregation of the dyes were also studied in different DMSO/water solution.