Synthesis and Properties of Cyclic Imide Extended Diazocines: Tweezer-Like, Rigid Photoswitches with Large Switching Amplitudes

Abstract

Diazocines are bridged azobenzenes with improved photophysical properties. One of the main features is the fact that, unlike the azobenzenes, the Z form is more stable than the E isomer. Another important property is the more rigid structure (tricyclic), which precisely defines the molecular movement. The disadvantage of diazocines compared to azobenzenes is the less well-developed chemistry, particularly regarding the synthesis of derivatives. In this work, we present an approach to preparing diazocine derivatives via a late-stage functionalization strategy. Two key compounds are used for this purpose: a bis-anhydride and a bis-imide of diazocine. They can be further functionalized with both nucleophiles and electrophiles leading to numerous derivatives of diazocine with a large range of functional groups. Due to the extended π systems, the associated larger molecular switching lever, and the defined direction of molecular movement, numerous potential applications in the field of photoswitchable biological systems and photoresponsive materials are conceivable, e.g. photopharmacology, polymer-based actuators, mechanophores, photoresponsive cages, helicates, MOFs, and COFs.