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 Δeff/kB = 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 Cr2Fe complex based on the same building units
and behaving as a SMM in zero field is also reported.