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Single Molecule Magnets light-switching with photochromic ligands

Periodic Reporting for period 2 - PhotoSMM (Single Molecule Magnets light-switching with photochromic ligands)

Reporting period: 2017-09-01 to 2018-08-31

The integration of molecular-scale components in circuits may ultimately allow the replacement of silicon-based electronics by high speed systems
with low energy consumption. Because of the prominent use of magnetization-based information storage technologies in our daily life, Single-
Molecule-Magnets (SMM), which are able to interconvert between two states with opposite magnetization directions receive a great deal of
attention. The potential is huge for SMM systems that would demonstrate magnetic field- and light-driven changes in both their optical and
magnetic properties because they could reproduce on a single molecule the same type of magneto-optical (MO) effects which are used for some
current data storage technologies. Photo-SMM focus on the effect of a light input on the magnetic and optical properties
of an SMM system based on a lanthanide ion.
During the one year outgoing phase at UC Berkeley, research work has been focused on the design and synthesis of new ligands and new lanthanide complexes adapted to the photoswitching of lanthanide-based systems.

1/ We have successfully prepared a new linker and the corresponding bimetallic complex. The light-switching behavior of these systems reveal a complex interplay between different parameters, the stability of the photo-induced isomer being impacted by i) metal coordination, ii) solvent or solid matrix environment. This unexpected result prompted us to investigate more into details these systems and theoretical calculations have been performed in collaboration with this aim.

2/ We have prepared new dysprosium complexes which support a terminal dysprosium-fluoride bond and demonstrated that such architectures are excellent in promoting strong axial magnetic anisotropy by combining luminescence, magnetism and ab initio calculations (in collaboration with Boris Le Guennic). The results have been communicated at the Europen Congress on Molecular Magnetism (Bucarest, August 2017), International Conference on Molecule Based Magnets (Rio, September 2018) and published in Angewandte Chemie.

During the return phase at Université de Rennes 1, research work has been focused on demonstrating a photomagnetic effect.

3/ Based on the work published in Angewandte Chemie, we could obtain a photo-switchable lanthanide complexes that demonstrate photomagnetic effect and therefore reach a central objective of PhotoSMM. Further structural characterization is being finalized before communication of the results.

4/ We have investigated the interplay between metal coordination and photochromism in the synthesized dinuclear complexes. This has involved NMR studies under irradiation. The final photomagnetic measurement will be carried out in the next future.

In line with the dissemination of results plan, I have attended four major international conferences to give oral presentations on my research work. I also participated to the outreach program “Festival des sciences” in the University of Rennes. Finally, the results of the first paper have been highlighted on the Université de Rennes 1 website, and on the CNRS website.
PhotoSMM has clearly given a boost to my research project and the development of my carrier.
It has allowed the discovery of a new type of SMM based on dysprosium-fluoride bonding, of totally unprecedented scaffolds for photoswitching and of new strategies for photomagnetism. Based on these innovative results, my research work will now focuss on the amplification of the photomagnetic effects observed for the first time thanks to PhotoSMM, and will receive support from the French Research Funding Agency with a PhD grant. During the project, I could also develop my international experience, my complementary skills on writing and mentoring and pass my habiliation diploma (HDR, habilitation à Diriger des Recherches) which concretizes the achievment of a position of professional maturity in research.