Design of a Library of Azo-pyridinic Derivatives as Building Blocks for Photoresponsive Materials

Azo-pyridinic derivatives are renowned for their ability to undergo reversible molecular switching when exposed to light. By combining the photoresponsive properties of azo-benzene with the supramolecular capabilities of pyridyl groups, azo-pyridines offer a route to develop multifunctional responsive materials through noncovalent interactions or reversible chemical reactions. Although azo-pyridine and its derivatives are commonly used in crystal engineering, their spectroscopic characterization is typically limited in solution and only poor attention has been given to their photoresponsive behavior in the solid state. Here, we present a library of azo-pyridinic derivatives designed as potential photoresponsive compounds with different spectroscopic behaviors based on the chemical decoration of the phenyl ring. Comprehensive characterization, including crystal structure, thermal analysis, and spectroscopic analysis, was performed for all compounds. Finally, their trans-to-cis isomerization propensity in the solid state is correlated with their crystal structures.