PHOTOCHEMISTRY IN STILBENE-CONTAINING MONOLAYERS .2. EFFECT OF CATION-BINDING ON PHOTOISOMERIZATION

A new stilbene-containing amphiphile with the chromophore in the hydro philic headgroup was synthesized, and the photoisomerization of the st ilbene sulfonate was investigated at the air-water interface. It could be shown that the isomerization leads to a decrease in area per molec ule. The binding of inorganic and organic cations from the subphase oc curs in the nanomolar concentration range. Binding was verified by UV and fluorescence spectroscopy and by electron spectroscopy for chemica l analysis. Upon complexation with alkaline earth metals, the stilbene photoisomerization proceeds apparently faster, whereas organic cation s of the viologen type quench the photoreaction. This is the first exa mple of a control of photoisomerization in monolayers by cation comple xation. (C) 1997 Elsevier Science B.V.