Effect of organic solvents on kinetics of J-aggregation and deaggregation of polymethine dyes in aqueous solution

The presence of organic solvents (acetonitrile, acetone, and dioxan) as additives (up to 5 vol %) in an aqueous solution of alkylmesothia- and oxacarbocyanine dyes containing KCl and/or Mg(NO3)2 results in a variation of the rate of both J-aggregation and deaggregation. The rate of J-aggregation is increased as well as decreased in the presence of organic solvents as additives. For thiacarbocyanine dye, increase of the additive concentration up to 3-5 vol % results in a decrease of the rate of J-aggregation, as well as an increase of the rate of deaggregation. For oxacarbocyanine, the presence of additives up to a critical concentration results in an increase of J-aggregation. At a higher than critical concentration, the rate of J-aggregation is decreased so that no J-aggregates are formed. © 2011 Pleiades Publishing, Ltd.