Molecular Switches Based on Spin-Crossover Metal Complexes

Spin-crossover (SCO) metal complexes are among the best known classes of molecular bistable systems. Their optical, magnetic and other physicochemical properties can be reversibly switched by changing the temperature, pressure, or irradiation with light. Although photoswitching in SCO complexes is well documented in the light-induced excited spin state trapping (LIESST) effect discovered in middle eighties, this effect is usually operative at low temperatures T < 50 K. This imposes serious limitations for its application in genuine photodevices.

We develop molecular photoswitches based on SCO metal complexes that overcome the low-temperature limitations of the LIESST effect. To achieve this we introduce photoactive ligands into SCO complexes in such a way that the photoisomerization of the ligand modifies the ligand field. This light-driven ligand-based modulation induces a spin transition at the coordinated metal ion that can be thus accomplished at room temperature. The reversibility of the photoswitching process can be utilized to design rewritable memories, whereas the addressing of the spin state at single molecule level may lead to the development of ultrahigh-density memory units. The present work is focused on the synthesis of photomagnetic molecular switches based on SCO metal complexes and investigation of their photomagnetic properties in solutions and in the solid state.

Research Molecule Diagram

Picture: M. Khusniyarov


Reversible Photoswitching of a Spin-Crossover Molecular Complex in the Solid State at Room Temperature.
B. Rösner, M. Milek, A. Witt, B. Gobaut, P. Torelli, R. H. Fink, M. M. Khusniyarov, Angew. Chem. Int. Ed. 2015, 54, 12976–12980. link

Spin Crossover Meets Diarylethenes: Efficient Photoswitching of Magnetic Properties in Solution at Room Temperature.
M. Milek, F. W. Heinemann, M. M. Khusniyarov, Inorg. Chem. 2013, 52, 11585–11592. link