Recent developments in light-induced spin crossover

Orateur : Guillaume CHASTANET (Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), CNRS-Univ. Bordeaux)

Photoswitchable molecules and materials have attracted a huge interest since the photoswitching may be ultrafast and operate at room temperature. 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]. 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.

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