Chemins d'interactions dans les composés magnétiques moléculaires à partir d'études de diffraction X haute résolution

Abstract : High resolution X-ray diffraction was used to model the electron density distribution in different molecular magnetic compounds, in which the interaction mechanisms are due to charge transfer, direct or indirect orbital overlaps, hydrogen bonds, electronic polarization or delocalisation. We have correlated the atomic electronic structure of these systems to their magnetic behavior and determined the exchange pathways from the topological analysis of the electron density. We have confirmed the implication of a charge transfer from the SOMO orbital to the LUMO orbital, according to the McConnell I mechanism, by intramolecular delocalisation and intermolecular hydrogen bonding in Nit(SMe)Ph. Three bond critical point in the three intermolecular hydrogen bonds, show the localization of the exchange pathways between radicals, responsible of the cooperativity of the system. 2D interactions by superexchange were characterized in CU2(OH)3N03, by the absence of bond critical , point between copper atoms. Interactions by high and low orbital overlap result from the participation of two hydroxo ions and one hydroxo and one nitrate ion to the exchange pathway respectively. Three hydrogen bonds, characterized by topological analysis, give rise to inter-plane couplings. An electronic delocalization was pointed out from the two metallic centers on the oxamato bridge in the ID ferrirnagrietic system MnCu(pba). The Cu-N and Cu-O bonds, involving higher orbital overlap than Mn-O, enable more efficient delocalization and polarization of the oxamato bridge. The topological analysis showed the implication of four hydrogen bonds in the inter-chairs couplings, explaining the deviation to a pure ID behavior at low temperature.
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http://docnum.univ-lorraine.fr/prive/SCD_T_2001_0020_PILLET.pdf
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Submitted on : Thursday, March 29, 2018 - 10:49:37 AM
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Sébastien Pillet. Chemins d'interactions dans les composés magnétiques moléculaires à partir d'études de diffraction X haute résolution. Autre. Université Henri Poincaré - Nancy 1, 2001. Français. ⟨NNT : 2001NAN10020⟩. ⟨tel-01747020⟩

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