Extension of the experimental electron density analysis to metastable states: a case example of the spin crossover complex Fe(btr)<sub>2</sub>(NCS)<sub>2</sub>.H<sub>2</sub>O - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal of the American Chemical Society Année : 2006

Extension of the experimental electron density analysis to metastable states: a case example of the spin crossover complex Fe(btr)2(NCS)2.H2O

Résumé

An experimental electron density (ED) analysis of the spin crossover coordination complex Fe(btr)2(NCS)2·H2O has been performed in the ground low-spin (LS) state and in the metastable thermally quenched high-spin (HS) state at 15 K by fitting a multipolar model to high-resolution X-ray diffraction measurements. The ED has been quantitatively analyzed using the quantum theory of atoms in molecules. This is the first time the ED distribution of a molecular metastable state has been experimentally investigated. The electron deformation densities and derived Fe 3d orbital populations are characteristic of LS (t2g6 eg0) and HS (t2g4 eg2) electron configurations and indicate significant σ donation to the Fe dx2-y2 and dz2 atomic orbitals. The Fe−NNCS and Fe−Nbtr coordination interactions are characterized using the laplacian distribution of the ED, the molecular electrostatic potential, and the fragment charges obtained by integration over the topological atomic basins. A combination of electrostatic and covalent contributions to these interactions is pointed out. Interlayer interactions are evidenced by the presence of bond critical points in N···H hydrogen bonds involving the non-coordinated water molecule. Systematic differences in the atomic displacement parameters between the LS and HS states have been described and rationalized in terms of modifications of bond force constants.
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Dates et versions

hal-01006886 , version 1 (22-11-2018)

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Vincent Legrand, Sébastien Pillet, Mohamed Souhassou, Noël Lugan, Claude Lecomte. Extension of the experimental electron density analysis to metastable states: a case example of the spin crossover complex Fe(btr)2(NCS)2.H2O. Journal of the American Chemical Society, 2006, 128 (42), pp.13921-13931. ⟨10.1021/ja064355f⟩. ⟨hal-01006886⟩
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