Combined Use of Magnetic Susceptibility Measurements and 57 Fe Mössbauer Spectroscopy To Determine the Magnetic Ground State of an Fe III 16 Cluster

A Strongly Spin-Frustrated Fe(III) 7 Complex with a Canted Intermediate Spin Ground State of S=7/2 or 9/2

A disk-shaped [Fe(III) 7 (Cl)(MeOH)6 (μ3 -O)3 (μ-OMe)6 (PhCO2 )6 ]Cl2 complex with C3 symmetry has been synthesised and characterised. The central tetrahedral Fe(III) is 0.733 Å above the almost co-planar Fe(III) 6 wheel, to which it is connected through three μ3 -oxide bridges. For this iron-oxo core, the magnetic susceptibility analysis proposed a Heisenberg-Dirac-van Vleck (HDvV) mechanism that leads to an intermediate spin ground state of S=7/2 or 9/2. Within either of these ground state manifolds it is reasonable to expect spin frustration effects. The (57) Fe Mössbauer (MS) analysis verifies that the central Fe(III) ion easily aligns its magnetic moment antiparallel to the externally applied field direction, whereas the other six peripheral Fe(III) ions keep their moments almost perpendicular to the field at stronger fields. This unusual canted spin structure reflects spin frustration. The small linewidths in the magnetic Mössbauer spectra of polycrystalline samples clearly suggest an isotropic exchange mechanism for realisation of this peculiar spin topology.

Undecametallic and hexadecametallic ferric oxo-hydroxo/ethoxo pivalate clusters

Synthesis strategies for highly condensed {Fe11} and {Fe16} pivalate clusters have been developed based on archetypal geometrically frustrated triangular {Fe3(μ3-O)} motifs that are interlinked via oxo, hydroxo, ethoxo, and carboxylate groups.

Exploring the no-man's land between molecular nanomagnets and magnetic nanoparticles

The comparison of the structural and magnetic properties of molecular nanomagnets (MNM) and magnetic nanoparticles (MNP) can be instructive to get a deeper understanding of the magnetic behavior on the intermediate scale between molecular and bulk objects. In this respect iron oxo based clusters are particularly interesting, since they provide an increasing number of molecular systems with sizes close to that of iron oxide MNP. In this Minireview we report a survey of literature data aimed at improving our understanding of the emergence of MNP properties from MNM ones.