Trinuclear Cyanido‐Bridged [Cr<sub>2</sub>Fe] Complexes: To Be or not to Be a Single‐Molecule Magnet, a Matter of Straightness
Céline Pichon, Nicolas Suaud, Valentin Jubault, Carine Duhayon, Nathalie Guihéry, Jean‐Pascal Sutter
Abstract
Abstract Trinuclear systems of formula [{Cr(L N3O2Ph )(CN) 2 } 2 M(H 2 L N3O2R )] (M=Mn II and Fe II , L N3O2R stands for pentadentate ligands) were prepared in order to assess the influence of the bending of the apical M−N≡C linkages on the magnetic anisotropy of the Fe II derivatives and in turn on their Single‐Molecule Magnet (SMM) behaviors. The cyanido‐bridged [Cr 2 M] derivatives were obtained by assembling trans ‐dicyanido Cr III complex [Cr(L N3O2Ph )(CN) 2 ] − and divalent pentagonal bipyramid complexes [M II (H 2 L N3O2R )] 2+ with various R substituents (R=NH 2 , cyclohexyl, S , S ‐mandelic) imparting different steric demand to the central moiety of the complexes. A comparative examination of the structural and magnetic properties showed an obvious effect of the deviation from straightness of the M−N≡C alignment on the slow relaxation of the magnetization exhibited by the [Cr 2 Fe] complexes. Theoretical calculations have highlighted important effects of the bending of the apical C−N−Fe linkages on both the magnetic anisotropy of the Fe II center and the exchange interactions with the Cr III units.