Influence of the counter-anion on the interaction of cations with the benzodithia-18-crown-6 butadienyl dye in monolayers

A strong influence of the counter-anions (such as Cl− and ClO42−) on the behavior of monolayers of an amphiphilic benzodithia-18-crown-6 butadienyl dye (dye 1) on aqueous subphases containing alkali metal or heavy metal cations (K+ or Hg2+) is demonstrated for the first time. Deduced from surface pressure-area and surface potential-area isotherms, reflection spectra and Brewster angle microscopy data, dye 1 monolayers show three types of structures depending on the counter-anion's influence on chromophore association and interactions with heavy and alkali metal cations.