Carbocyanine Dyes with an o-Hydroxyaryl Substituent in the Meso Position of the Polymethine Chain

Article abstract of DOI:10.1007/BF00475576

Carbocyanine dyes with an o-hydroxyaryl substituent in the meso position of the polymethine chain were obtained from o-hydroxybenzoyl derivatives of the Fischer base and heterocyclic methylene bases (1,3,3-trimethyl-2-methyleneindoline, 1-ethyl-4-methylene-1,4-dihydroquinoline) and 1-methyl-2-methylene-1,2-dihydroquinoline in the presence of phosphorus oxychloride.The symmetrical indolenine dyes exist in the colorless spiropyran form in an alkaline medium.The unsymmetrical carbocyanines with a quinoline fragment do not form a spiro form and are deeply colored compounds; this is explained by their open dipolar structure.