Acid-base-induced → isomerization of luminescent iridium(iii) complexes.

Luminescent Ir(C^N) complexes (C^N = cyclometalated arylpyridine ligand) exist in the form of two stable isomers with distinct photophysical and electrochemical properties: and . Herein, we show that -Ir(C^N) complexes can be converted into the thermodynamically less stable forms by a consecutive reaction with first acid and then base. The chemically induced isomerization is fast, quantitative, and stereoselective, and it can be inversed by light.