Kinetics of J-aggregation of a thiacarbocyanine dye in aqueous solution: Novel aggregate mediated by alcohols and metal ions

The kinetics of formation of J-aggregates induced by mono-, di- and trivalent metal ions was studied for 3,3′-di(γ-sulfopropyl)-5-methoxy-4′,5′-benzo-9-ethylthiacarbocyanine in aqueous solution in the presence of organic solvents, e.g., acetonitrile, where the rate is strongly decreased. A novel intermediate aggregate (I-aggregate) was observed, when a metal ion was added to the thiacarbocyanine dye in a mixture of water with alcohols. The I- and J-aggregates are formed from the dimers. The kinetics of formation of the I-aggregate depend on the concentrations of alcohol and metal ions and its decay matches the formation of the modified J-aggregate.