The synthesis and characterization of novel, aza-substituted squarylium cyanine dyes

Several squarylium cyanine dyes derived from benzothiazole, benzoselenazole and quinoline were synthesised and the central four member ring functionalized by substitution of one of the oxygen atoms by benzylamine, aniline, 3-iodoaniline, N,N-dimethylhydrazine and 2-aminosulfonic acid groups. All of the ensuing, novel aza-substituted dyes displayed strong absorption within the range 651–709 nm.