Louis Caussin PhD defense

Abstract
Single-chain magnets exhibit magnetic bistability at the molecular scale and hold promise for high-density information storage. Controlling them with light would provide an additional level of control. This work combines dithienylethene photochromic units, nitronyl-nitroxide radicals, and lanthanide(III) ions, with photoisomerization intended to modulate both magnetic exchange interactions and the ligand field around the metal.
Four dithienylethene–nitronyl-nitroxide diradicals and three monoradical analogs were synthesized and characterized. The most compact diradical, previously unreported, exhibits an antiferromagnetic exchange interaction multiplied by a factor of 100 upon ring closure—the strongest reported to date for this family—as well as the first ON/OFF photomodulation of the luminescence of a nitronyl-nitroxide radical.
The coordination of these ligands to lanthanide(III) ions led to the first complexes integrating dithienylethene–nitronyl-nitroxide units, in both open and closed forms. Their photochromic and magnetic properties were studied, particularly using torque magnetometry.
These results lay the foundation for the development of photocommutable single-chaine magnets based on radicals.

Jury
Jennifer Molloy, CNRS researcher, University Grenoble Alpes
Ie-Rang Jeon, CNRS researcher, University of Bordeaux
David Canevet, Professor, University of Angers
Mauro Perfetti, Professor, University of Florence
Lucie Norel, Professor, ISCR, University of Rennes / PhD Director
Kevin Bernot, Professor, INSA Rennes, ISCR, University of Rennes / PhD Co-Director

Contacts
[Louis Caussin](https://iscr.univ-rennes.fr/louis-caussin), [Louis.caussin@univ-rennes.fr](mailto:Louis.caussin@univ-rennes.fr)
[Lucie Norel](https://iscr.univ-rennes.fr/lucie-norel), [lucie.norel@univ-rennes.fr](mailto:lucie.norel@univ-rennes.fr)
[Kevin Bernot](https://iscr.univ-rennes.fr/kevin-bernot), [kevin.bernot@univ-rennes.fr](mailto:kevin.bernot@univ-rennes.fr)