Topic: Spin Crossover Particles: Exploring New Processes for the Synthesis of Nanoparticles and Nanocomposites
Speaker: Professor Guillaume Chastanet - University of Bordeaux
Host: Professor Selvan Demir
Date: Monday, December 2, 2019
Time: 11:20 AM
Location: 136 CEM
Switchable molecules and materials have attracted a huge interest since the switching can occur at room temperature between two long lived states, especially using ultrafast photoswitching. Spin crossover (SCO) phenomenon based on an electronic configuration switch stimulated by temperature, light or pressure has been widely studied for this purpose. In SCO compounds, there are three ways of photoswitching one state into another[1,2]. A photoreaction on a ligand can be promoted (photo-isomerization or cyclization) consequently tuning the ligand field and the global SCO behavior. This is typically the case of the Ligand-Driven Light-Induced Spin Change (LD-LISC) and the Light-Driven Coordination-Induced Spin-State Switching (LD-CISSS) phenomena. When the wavelength is set on the metallic d-d bands or metal-ligand charge transfer transitions, some transient excited states can be populated leading to the photo-induced spin-state switching. This is the case of the widely studied Light-Induced Excited Spin-State Trapping (LIESST) effect. Finally, there is a third action of light related to the energy deposited onto the material. Depending on the number of photons, a strong heating may occur, leading to photo-thermal effects that allows the occurrence of spin-crossover transition.
More than 30 years of efforts have been devoted to the understanding of the photoswitching process and the lifetime of the photoinduced state in order to improve the temperature at which it can be observed. In the last 10 years many efforts have been devoted to the elaboration of nanosized systems, especially for their integration in electronic devices. This presentation will present several chemical processes, from the classical micelle synthesis to the flow chemistry approach, explored for the synthesis of nanoparticles. A specific attention will be brought to the synthesis of nanocomposite for the ultrafast and weakly energetic photoswitching around room temperature.
 G. Chastanet, M. Lorenc, R. Bertoni, C. Desplanches, C. R. Chimie. 2018, 21, 1075.
 G. Chastanet, C. Desplanches, C. Baldé, P. Rosa, M. Marchivie, P. Guionneau, Chem. Sq.. 2018, 2, 1
Acknowledgements: CNRS, University of Bordeaux, ANR program (HEROES: ANR-17-CE09-0010-01), Aquitaine Region.
Guillaume CHASTANET, summary
Guillaume Chastanet has started his research on molecular magnetism by a PhD tesis (supervised by the late Olivier Kahn and Jean-François Létard) defended in 2002 on the photomagnetism of spin crossover materials. After a 2 years post-doc positions in Florence in the Dante Gatteschi’s laboratory, he joined the CNRS as permanent researcher in Lyon at the Laboratory of Multimaterials and Interfaces, in the group of Dominique Luneau. From 2003 to 2009 he dedicated his activities to Single Molecule Magnets and magnetic materials. In 2009 he integrated the Institute of Chemistry of Condensed State Matter of Bordeaux, in the group of Jean-François Létard, dedicating his research to spin crossover materials, their photoswitching and their downsizing as nanoparticles. Since 2014 he is leading the Switchable Molecules and Materials group (9 permanents researchers) and since 2016 he is directing the French network of Molecular Magnetism and Switching (50 french research teams).