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Magnétisme photo-induit dans de nouveaux matériaux dérivés des octacyanométallates

Abstract : The control of a physical property by an external stimulus is an active research topic in the field of molecular sciences. This work deals with the influence of a light excitation upon the magnetic properties of molecule-based compounds in the solid state. We used the octacyanometalate precursors Miv,v(CN)8n-(M=Mo,W ; n = 3,4) as building blocks because they present, i) an oxidation state flexibility of the metal centre corresponding to two different spin states with the same local surrounding, ii) a photo-oxidation property of the metal ion leading to a change from a diamagnetic state (MIV) to a paramagnetic one (MV) under light irradiation in the UV range. These two properties allowed us to develop two different strategies to obtain new photomagnetic materials. The compounds synthesised have been characterised by single crystal X-ray diffraction, powder X-ray diffraction, wide angle X-ray scattering (WAXS) and X-ray absorption spectroscopy techniques. The photomagnetic studies have shown two different behaviours depending on the nature of the compounds and the range of wavelenght used during the photo-excitation. Thus, we observed, for example, for the compound cuII2[MoIV(CN)8].7.5H20 a change from a paramagnetic to an ordered ferromagnetic state under light irradiation due to a photo-induced electron transfer between the metal centers.
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Guillaume Rombaut. Magnétisme photo-induit dans de nouveaux matériaux dérivés des octacyanométallates. Matériaux. Université Sciences et Technologies - Bordeaux I, 2001. Français. ⟨tel-00010259⟩

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