A Strongly Spin‐Frustrated FeIII7 Complex with a Canted Intermediate Spin Ground State of S=7/2 or 9/2

E-ISSN： 1521-3765|21|30|10835-10842

ISSN： 0947-6539

Source： CHEMISTRY - A EUROPEAN JOURNAL, Vol.21, Iss.30, 2015-07, pp. : 10835-10842

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Abstract

AbstractA disk‐shaped [FeIII7(Cl)(MeOH)6(μ3‐O)3(μ‐OMe)6 (PhCO2)6]Cl2 complex with C3 symmetry has been synthesised and characterised. The central tetrahedral FeIII is 0.733 Å above the almost co‐planar FeIII6 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 57Fe Mössbauer (MS) analysis verifies that the central FeIII ion easily aligns its magnetic moment antiparallel to the externally applied field direction, whereas the other six peripheral FeIII 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.