Magnetic Properties of Two New Fe-4 Single-Molecule Magnets in the Solid State and in Frozen Solution

Christoph Schlegel, Enrique Burzuri, Fernando Luis, Fabrizio Moro, Maria Manoli, Euan K. Brechin, Mark Murrie, Joris van Slageren

Research output: Contribution to journalArticlepeer-review


Two novel tetranuclear, star-shaped iron(III) clusters, [Fe-4(acac)(6)-(Br-mp)(2)] and [FeIII4(acac)(6)(tmp)(2)], are described. Both have S=5 ground states resulting from antiferromagnetic nearest-neighbour superexchange interactions, with J=-8.2 cm(-1) and J=-8.5 cm(-1) for 1 and 2, respectively. Energy barriers for the relaxation of the magnetisation of approximately 12 cm(-1) were derived from AC suscept-ibility measurements. Magnetic resonance measurements revealed a zero-field splitting parameter D=-0.34 cm(-1) for both complexes. AC susceptibility measurements in solution demonstrated that the complexes are reasonably stable in solution. Interestingly, the magnetisation relaxation slows down significantly in frozen solution, in contrast to what is generally observed for single-molecule magnets. This was shown to result from a large increase in tau(0), the prefactor in the Arrhenius equation, with the energy barrier remaining unchanged.

Original languageEnglish
Pages (from-to)10178-10185
Number of pages8
JournalChemistry - A European Journal
Issue number33
Publication statusPublished - 3 Sep 2010


  • cluster compounds
  • EPR spectroscopy
  • magnetic properties
  • magnetisation relaxation
  • molecular magnetism


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