Cyano-Bridged Fe(II)-Cr(III) Single-Chain Magnet Based on Pentagonal Bipyramid Units: On the Added Value of Aligned Axial Anisotropy

A cyano-bridged Fe(II)-Cr(III) single-chain magnet designed to ensure a parallel orientation of the axial anisotropy of the building units is reported. This ferromagnetic chain compound consists of a pentagonal bipyramid Fe(II) complex with Ising-type anisotropy and a dicyanide Cr(III) complex interlinked through their apical positions. It is characterized by an energy gap for the magnetization reversal of Delta(eff)/k(B) = 113 K and exhibits magnetic hysteresis with a coercive field of 1400 Oe at 2 K which positions this compound among the very few examples of SCMs with spin reversal barriers above 100 K The quite remarkable performances of this single-strand SCM are attributed to the alignment of the local anisotropy axes, which is supported by ab initio modeling. A discrete Cr,Fe complex based on the same building units and behaving as a SMM in zero field is also reported.