Switching Process Consisting of Three Isomeric States of an Azobenzene Unit.

Azobenzene and its derivatives are among the most commonly used switching units in organic chemistry. The switching process consists of two states, in which the trans isomer has a stretched and the cis isomer a compact form. Here, we have designed a system in which all isomeric states of an azobenzene moiety (trans → cis-(M) → cis-(P)) are passed step by step. The first step involves a change in the distance between the benzene units, which is common for azobenzene derivatives. In the second step an inversion of the helicity (M→P) of the cis azobenzene unit takes place. The third step leads back to the stretched trans isomer. This switching cycle is achieved by coupling the azobenzene unit with two chiral clamps and with a further azobenzene switching unit.