Spatially Controlled Photoisomerizability of Azobenzene Moieties in Langmuir-Blodgett Monolayers of Ion-Paired Macrocyclic Amphiphiles

Abstract

Monolayers of ternary ion-paired macrocyclic amphiphiles consisting of a tetracationic cyclophane and two kinds of sulfonate surfactants with an azobenzene unit and either a single or double long chain alkyl unit were prepared by a Langmuir-Blodgett technique to elucidate the structure/property relation between a free space surrounding an azobenzene moiety and photoisomerizability in monolayers. It was found that an azobenzene unit with a hexyl group needs a minimum occupied area of about 0.5 nm2 for sufficient E/Z photoisomerization.