Gernot Heitmann, Christian Schütt, Rainer Herges


We herein report the synthesis and switching properties of an azo‐1‐methylimidazole‐functionalized Ni2+ porphyrin. Upon irradiation and cis/trans isomerization of the azo unit, 1‐methylimidazole is reversibly coordinated as an axial ligand to the Ni2+ porphyrin. Consequently, the Ni2+ is switched between a diamagnetic low‐spin state (trans) and a paramagnetic high‐spin state (cis) according to the light‐driven coordination‐induced spin state switching (LD‐CISSS) principle. The spin state switching is operable in solution under ambient conditions. The paramagnetic cis‐species is formed in exceptionally high amounts upon irradiation with UV light (365 nm), whereas an excess of the diamagnetic trans‐species was obtained upon irradiation with blue light (430 nm).