Effect of multiply charged paramagnetic metal cations on J-aggregation of thiacyanine dyes

J-Aggregation of thiacyanine dyes with a different length of the polymethine chain has been studied in aqueous solutions in the presence of paramagnetic metal cations. The introduction of multiply charged metal cations stimulates J-aggregation. The number of molecules involved in the composition of J-aggregates has been calculated to be four on the basis of analysis of the absorption spectra. The equilibrium constants and the thermodynamic parameters of J-aggregation have been determined. The effect of the dye structure and the metal cation nature on J-aggregation has been revealed.