Neue Dimethinmerocyaninfarbstoffe mit J‐Aggregation in stark verdünnter Lösung

Novel Dimethinmerocyanine Dyes Performing J‐Aggregation in Highly Diluted Solution A series of various novel long‐chain alkyl‐dimethinmerocyanine dyes containing sulfonate groups is obtained in high yield by modified condensation reactions of sulfoalkyl‐ or sulfophenylsubstituted methylene ketones. The dyes exhibit intense, red‐shifted absorption bands (ϵ up to 263 000) due to J‐aggregation in DMSO/H2O mixtures without addition of salt even at dye concentrations of 5 · 10−8M. The influence of dye structure and medium on the aggregation tendency is investigated. Besides it is found that exchange of the cationic counterions does not affect J‐aggregation.