Development and Investigation of Photoswitchable Molecular Magnets Based on Quinonoid Ligands
Final Report Abstract
The aim of this project was to develop novel switchable molecular magnetic materials. Such materials could one day find application in novel ultrahigh-density magnetic data storage devices. To this end a large variety of novel complexes was synthesized and characterized. The application of a wide arsenal of physical measurement methods allowed the elucidation and detailed understanding of the magnetic properties of the novel compounds. We were able to switch the magnetic properties of the complexes under the influence of visible light irradiation and under the influence of electrochemical processes. Serendipitously, we also found a novel cobalt single-ion magnet with record breaking magnetic properties. The biggest surprise during this project was the discovery of a mononuclear complex with superior single-molecule magnet properties. The relevant complex was a byproduct of a related investigation. During the magnetic characterization we rapidly realized that its magnetic properties were highly unusual and extraordinarily favorable. Thus it possesses the largest energy barrier toward relaxation of the magnetic moment ever reported for a cobalt(II) complex and the second highest for any mononuclear transition metal complex. In addition, the compounds displays substantial coercivity, leading to the magnetic bistabilty required for data storage applications. Through a combined spectroscopic and ab initio theoretical study we were able to fully understand the origin of these favorable properties: The strong elongation of the complex along a certain axis leads to a strong splitting of the lowest excited state, one component of which approaches the electronic ground state very closely as a result. The consequence is a strong magnetic anisotropy leading to a large effective energy barrier. This has allowed us to formulate a design criterion for novel and improved single-ion magnets. We are now using this building block to develop polynuclear species, where we aim to improve the coercivity of the system. One Publication (Nat. Commun. 2016) drew interest from many sides. It led to Van Slageren being interviewed by Rundfunk Berlin-Brandenburg on 27 February 2016 (http://media-streampmd.rbb-online.de/content/a1f1c40e-ac56-46ec-ba81-7294b5b5b005_2ba18eed-f2a4-4c00-9451-06a9e6c17dde.mp3). It was highlighted on many internet sites, including chemie.de (http://www.chemie.de/news/156968/), www.innovations-report.de, www.myscience.org, www.pro-physik.de, www.molmag.de, www.wissenschaftsmanagement.de, spotfolio.com, http://www.advancedsciencenews.com.
Publications
- (Electro)catalytic C-C Bond Formation Reaction with a Redox-Active Cobalt Complex , Chem. Commun., 50, 11104 – 11106 (2014)
M. van der Meer, Y. Rechkemmer, I. Peremykin, S. Hohloch, M.G. Sommer, J. van Slageren, B. Sarkar
(See online at https://doi.org/10.1039/c4cc03309d) - Redox-Induced Spin State Switching and Mixed-Valency in Quinonoid Bridged Dicobalt Complexes, Chem. Eur. J., 20, 3475 – 3486 (2014)
D. Schweinfurth, Y. Rechkemmer, S. Hohloch, N. Deibel, I. Peremykin, J. Fiedler, J. van Slageren, and B. Sarkar
(See online at https://doi.org/10.1002/chem.201302858) - A Dicobalt Complex with an Unsymmetrical Quinonoid Bridge Isolated in Three Units of Charge: A Combined Structural, (Spectro)-electrochemical, Magnetic and Spectroscopic Study, Chem. Eur. J., 22, 13884 – 13893 (2016)
M. van der Meer, Y. Rechkemmer, U. Frank, F.D. Breitgoff, S. Hohloch, C.-Y. Su, P. Neugebauer, R. Marx, M. Dörfel, J. van Slageren, B. Sarkar
(See online at https://dx.doi.org/10.1002/chem.20161579) - A Four-Coordinate Cobalt(II) Single Ion Magnet With Coercivity and a Very High Energy Barrier, Nat. Commun., 7, 10467 (2016)
Y. Rechkemmer F.D. Breitgoff, M. van der Meer, M. Atanasov, M. Hakl, M. Orlita, P. Neugebauer, F. Neese, B. Sarkar, J. van Slageren
(See online at https://doi.org/10.1038/ncomms10467) - Multiple Bistability in Quinonoid-Bridged Diiron(II) Complexes: Influence of Bridge Symmetry on Bistable Properties, Inorg. Chem., 55, 11944 – 11953 (2016)
M. van der Meer, Y. Rechkemmer, F.D. Breitgoff, R. Marx, P. Neugebauer, U. Frank, J. van Slageren, B. Sarkar
(See online at https://doi.org/10.1021/acs.inorgchem.6b02097) - Probing Bistability in FeII and CoII Complexes with an Unsymmetrically Substituted Quinonoid Ligand, Dalton Trans., 45, 8394 – 8403 (2016)
M. van der Meer, Y. Rechkemmer, F. Breitgoff, S. Dechert, R. Marx, M. Dörfel, P. Neugebauer, J. van Slageren, B. Sarkar
(See online at https://doi.org/10.1039/c6dt00757k) - Storing Information at the Molecular Level: Developing Molecules for Data Storage Devices. G.I.T. Laboratory Journal 2016, December 09
B. Sarkar and J. van Slageren
(See online at https://doi.org/10.1016/j.chempr.2016.06.014) - Structural Snapshots in the Copper(II) Induced Azide-Nitrile Cycloaddition: Effect of Peripheral Ligand Substituents on the Formation of Unsupported µ1,1-Azido vs. µ1,4-Tetrazolato Bridged Complexes, Dalton Trans., 45, 17770 – 17781 (2016)
M.G. Sommer, Y. Rechkemmer, L. Suntrup, S. Hohloch, M. van der Meer, J. van Slageren, B. Sarkar
(See online at https://doi.org/10.1039/c6dt03073d) - Control of Complex Formation through Peripheral Substituents in Click-Tripodal Ligands: Structural Diversity in Homo-and Heterodinuclear Cobalt-Azido Complexes, Inorg. Chem., 56, 402 – 413 (2017)
M.G. Sommer, R. Marx, D. Schweinfurth, Y. Rechkemmer, P. Neugebauer, M. van der Meer, S. Hohloch, S. Demeshko, F. Meyer, J. van Slageren, B. Sarkar
(See online at https://doi.org/10.1021/acs.inorgchem.6b02330)
