Artificial Iono- and Photosensitive Membranes Based on an Amphiphilic Aza-Crown-Substituted Hemicyanine

Artificial iono- and photosensitive membranes based on an amphiphilic aza-crown-substituted hemicyanine are assembled on liquid and solid supports and their aggregation behaviour, which is influenced by the binding of metal cations and surface density, is studied. The photoinduced charge-transfer properties of an analogous non-amphiphilic hemicyanine in solution are also demonstrated. An asymmetric sandwich dimer model is proposed and existence of such dimers in solution is evidenced by transient absorption and fluorescence anisotropy experiments. Changes in absorption and emission spectra, as well as compression isotherms of the amphiphile observed in the presence of cations, are discussed in terms of 2D molecular reorganisation. Surface-pressure-controlled reversible excimer formation at the air-water interphase and excimer-type emission of Langmuir-Blodgett films in the presence of cations are demonstrated and are discussed on the basis of fibre-optic fluorimetry and fluorescence microscopy results.