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

作者：Mondal Kartik Chandra; Mereacre Valeriu; Kostakis George E; Lan Yanhua; Anson Christopher E; Prisecaru Ion^*; Waldmann Oliver; Powell Annie K

来源：Chemistry - A European Journal, 2015, 21(30): 10835-10842.

DOI：10.1002/chem.201500841

• magnetic properties
• Mossbauer spectroscopy
• polynuclear iron complexes
• spin frustration

A disk-shaped [Fe-7(III)(Cl)(MeOH)(6)((3)-O)(3)(-OMe)(6) (PhCO2)(6)]Cl-2 complex with C-3 symmetry has been synthesised and characterised. The central tetrahedral Fe-III is 0.733 angstrom above the almost co-planar Fe-6(III) wheel, to which it is connected through three (3)-oxide bridges. For this iron-oxo core, the magnetic susceptibility analysis proposed a Heisenberg-Dirac-vanVleck (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 Fe-57 Mossbauer (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 Mossbauer spectra of polycrystalline samples clearly suggest an isotropic exchange mechanism for realisation of this peculiar spin topology.

• 出版日期2015-7-20