Molecular Switches Based on Valence Tautomeric Metal Complexes

Similarly to spin-crossover metal complexes, valence tautomeric (VT) metal complexes offer great opportunity to control their magnetic and other physicochemical properties by external stimuli. The switching of the electronic structure and associated properties in VT systems with light is difficult to achieve: temperatures below 20 K are generally required to stabilize photoinduced states.

By introducing highly efficient and robust organic photochromes into VT complexes we create “smart” molecular systems that allow controlling the spin and oxidation state of coordinated metal ions and thus the associated magnetic properties of materials with light at room temperature. Similarly to spin-crossover metal complexes, reversibility of the photoswitching process can be utilized to design rewritable memories, whereas the addressing of spin and oxidation states at single molecule level can lead to the development of ultrahigh-density memory units. Presently, we work on the synthesis of photomagnetic molecular switches based on valence tautomeric complexes of cobalt and investigation of their physicochemical and photomagnetic properties both in solution and in the solid state.


Bidirectional Photoswitching of Magnetic Properties at Room Temperature: Ligand-Driven Light-Induced Valence Tautomerism.
A. Witt, F. W. Heinemann, M. M. Khusniyarov, Chem. Sci. 2015, 6, 4599–4609. link

Modulation of Magnetic Properties at Room Temperature: Coordination-Induced Valence Tautomerism in a Cobalt Dioxolene Complex.
A. Witt, F. W. Heinemann, S. Sproules, M. M. Khusniyarov, Chem. Eur. J. 2014, 20, 11149–11162. link