Synthesis and photochemical properties of an anion receptor containing azocarboxamide groups

Many anion receptors have been developed for selective recognition and binding of a specific negatively charged species. Their structure usually contains covalently linked groups with high affinity towards the desired ions [1]. The binding ability of the receptor for an anion in specific solvent once defined by its structure usually cannot be changed using external stimuli. In recent years there have been a few examples of responsive receptors which utilize groups capable of changing the affinity towards an anion in the presence of external stimuli [2]. They are comprised of photochromic moieties which have been till recently almost exclusively studied with larger guests [3]. That is in part because it is easier to prepare receptors in which photoresponsive change in the architecture controls binding of larger species as compared to small anions. Herein we present an anionic receptor with photoresponsive host‐guest properties designed for small anions. Basic motion is achieved through E‐Z isomerization of azocarboxamide. The simplest aromatic derivative containing azocarboxamide as well as photochemical isomerization is shown below.