Unsymmetrical indamine dyes have been synthesized by the reaction of 2,2′-bis(dialkylamino)-4,5′-bithiazoles with 4-nitrosoanilines followed by heating with metal salts. The first UV/vis absorption bands of indamine dyes were observed at λ = 648–725 (e = 3900–55000) nm in dichloromethane, being more bathochromic than those of the corresponding cyanine derivatives. The chromophoric system for these
Unsymmetrical indamine dyes have been synthesized by the reaction of (diethylamino)thiazole dimer with 4-nitrosoanilines followed by heating with metal salts. The chromophoric system for these indamine dyes was described as the mixture of the π–π* transition coming from the alternant chromophore inside the bithiazolyl moiety and the charge-transfer from anilino to bithiazolyl moieties.