Azobenzene Macrocycles: Synthesis of a Z-Stable Azobenzenophane

Azobenzenes have attracted increasing attention in the past years due to their application as molecular switches. In this report, we present a macrocyclic bisazobenzene that exists as the stable Z-isomer. The synthetic efforts as well as the successful strategy are discussed. Final ring closure under continuous irradiation gave the (Z, Z)-bisazobenzenophane. This Z-azobenzene does not show any isomerization under either heating or prolonged irradiation. The thermal stability of the Z-form has also been supported by computations. The prepared bisazobenzenophane represents one of the few azobenzenes in which the Z-isomer is more stable than the E-isomer.