Spatially controlled photoisomerizability of azobenzene moieties in Langmuir-Blodgett monolayers of ion-paired macrocyclic amphiphiles

Monolayers of ternary ion-paired macrocyclic amphiphiles consisting of a te tracationic cyclophane and two kinds of sulfonate surfactants with an azobe nzene unit and either a single or double long chain alkyl unit were prepare d by a Langmuir-Bladgett technique to elucidate the structure/property rela tion between a free space surrounding an azobenzene moiety and photoisomeri zability in monolayers. It was found that an azobenzene unit with a hexyl g roup needs a minimum occupied area of about 0.5 nm(2) for sufficient E/Z ph otoisomerization.