Synthesis and Properties of Photomagnetic Molecular Switches based on Spin Crossover Iron(II) Complexes Featuring Photoisomerizable Ligands
Final Report Abstract
Recently, we developed a unique spin-crossover molecular switch 1 that allows the reversible change of magnetic properties by action of light at room temperature. The photoswitching achieved in solution proceeds at molecular level. In this project, we explored chemical modifications of 1 and photoswitching in solutions, solid state, thin films, und sub(monolayers). The attempted modification at a photoisomerizable diarylethene unit leaded to a significant decrease of the thermal stability of the photoswitch. However, modifications at the metal coordinating site – phenanthroline – leaded to increased or decreased thermal stability of the photoswitch, depending on introduced substituents. All attempted modifications resulted in decreased photomagnetic effect in solution at room temperature. Reversible photomagnetic effect was achieved with 1 in the solid state at room temperature. It corresponds to a high-spin state (paramagnetic) to a low-spin state (diamagnetic) photoconversion of 32%. Functional thin films of 1 on gold substrate were produced by evaporation in ultra-high vacuum. Photoswitching of molecular spin-crossover complexes in thin films was demonstrated at room temperature for the very first time. A general synthetic approach towards asymmetric phenanthrolines featuring unequal substituents at positions 3 and (5,6) was developed, which has opened the route towards numerous novel phenanthroline derivatives. This approach might be useful not only for the prospective synthesis of phenanthroline-based molecular switches capable of chemisorption, but also for diverse applications of phenanthroline systems in surface chemistry, catalysis, biochemistry, and biology. Some of our results were reported in media: https://www.fau.de/files/2014/07/fau_magazin_alexander_100.pdf https://www.fau.de/2015/09/news/wissenschaft/magnetisch-durch-licht/ https://www.elettra.trieste.it/science/top-stories/reversible-photoswitching-of-a-spin-crossover-molecular-complex-in-the-solid-state-at-room-temperature.html
Publications
- Light-Induced Spin-Crossover. Elsevier Reference Module in Chemistry, Molecular Sciences and Chemical Engineering (Ed.: J. Reedijk). Waltham, MA: Elsevier, 2015
M. M. Khusniyarov
(See online at https://doi.org/10.1016/B978-0-12-409547-2.11540-9) - Reversible Photoswitching of a Spin-Crossover Molecular Complex in the Solid State at Room Temperature. Angew. Chem. Int. Ed. 2015, 54, 12976–12980
B. Rösner, M. Milek, A. Witt, B. Gobaut, P. Torelli, R. H. Fink, M. M. Khusniyarov
(See online at https://doi.org/10.1002/anie.201504192) - How to Switch Spin-Crossover Metal Complexes at Constant Room Temperature. Chem. Eur. J. 2016, 22, 15178–15191
M. M. Khusniyarov
(See online at https://doi.org/10.1002/chem.201601140) - Synthesis, Characterization and Properties of Iron(II) Spin-Crossover Molecular Photoswitches Functioning at Room Temperature. Inorg. Chem. 2017, 56, 13174–13186
M. Mörtel, A. Witt, F. W. Heinemann, S. Bochmann, J. Bachmann, M. M. Khusniyarov
(See online at https://doi.org/10.1021/acs.inorgchem.7b01952) - Room Temperature Control of Spin States in a Thin Film of a Photochromic Iron(II) Complex. Materials Horizons 2018, 5, 506–513
L. Poggini, M. Milek, G. Londi, A. Naim, G. Poneti, L. Squillantini, A. Magnani, F. Totti, P. Rosa, M. M. Khusniyarov, M. Mannini
(See online at https://doi.org/10.1039/c7mh01042g)
