dyes

The formation of associates in aqueous solutions between single- or double-charged anions of 5,5′-dibromo-o-cresolsulfonphthaleine and single-charged cations of cyanine dyes (quinaldine blue, quinaldine red) has been considered. Based on the spectrophotometric data, the equilibrium constants of the association were analyzed. The energy of cation-anion interactions (standard enthalpy of formation of ions and associates) was determined by the semi-empirical AM1 method and probable structures of associates were set.

The formation of associates between one- or two-charged anions of sulfonephthalein dyes – thymolsulfonephthalein, cresolsulfonephthalein – and cyanine cations (pinacyanol, quinaldine red) has been considered in aqueous solution. Equilibrium association constants have been determined using spectrophotometric data. By semiempirical methods the enthalpy of formation and the eventual structure of ions and associates have been established.