Phenothiazine-bipyridinium cyclophanes

The syntheses of oligooxa[8,8]-, -[11,11]-, -[14,14]-, -[17,17]- and -[20,2 0]cyclophanes with phenothiazine as donor and bipyridinium. dication as acc eptor are described, together with preparations of the corresponding oligom ethylene-[3,3]- and -[4.4]cyclophanes. While the large [8,8]-, [11,11]- and [14,14]cyclophanes in particular show well-defined charge-transfer (CT) ab sorption maxima, the smallest [3,3]cyclophane does not exhibit any CT effec t. For the large cyclophanes, a preferred conformation with crossed donor a nd acceptor units is proposed. The fluorescence quenching and electrochemic al behaviour of all phenothiazine-bipyridinium cyclophanes is discussed.