Light‐Promoted Basic Nitrogen Unmasking in Arene Ruthenium Complexes Derived from Z ‐Configured 2,2′‐Azobispyridine

Abstract Two novel 2,2′‐azobispyridine derivatives bearing N ‐dialkylamino substituents at position 4,4′ were synthesized and their E – Z photoswitching behavior was characterized by combination of 1 H‐ and 13 C NMR spectroscopy, UV–Vis absorption and DFT calculations. Both isomers act as ligands towards arene‐Ru II centers, leading either to E ‐configured 5‐membered chelates (involving coordination of nitrogen atoms from N=N bond and pyridine) or to the uncommon Z ‐configured 7‐membered chelates (involving coordination of nitrogen atoms from both pyridines). The latter show good stability in the dark, allowing single crystal X‐ray diffraction study to be reported here for the first time. All synthesized Z ‐configured arene‐Ru II complexes undergo irreversible photo‐isomerization to their corresponding E isomers with rearrangement of their coordination pattern. This property was advantageously exploited for the light‐promoted unmasking of a basic nitrogen atom of the ligand.