Über den Einfluss des Donor‐Teilchromophors bei Dimethinmerocyanin‐Farbstoffen auf das Aggregationsverhalten in wässriger Lösung

On the Influence of the Donor Part of the Chromophor of Dimethinmerocyanine Dyes upon the Aggregation Tendency in Aqueous Solution A series of novel long‐chain alkyl‐dimethinmerocyanine dyes containing the (rhodaninyl)benzenesulfonate or (cyanoacetoxy)alkanesulfonate group is synthesized in good yield and their aggregation tendency in H2O and/or in various organic solvents/H2O mixtures without addition of salt investigated. Except for the merocyanine 2h, all dyes give J‐aggregation in H2O or in organic solvents containing H2O. The Lambert‐Beer rule is proved for the solution of 3a(4) in H2O. The degree of aggregation of 3a(4) in H2O is investigated by ultracentrifugation. The kind of the aggregation (J‐ or H‐type) can be found out very quickly by dissolving the dye in H2O with the help of ultra‐sound.