EPR characterization of half-integer-spin iron molecule-based magnets

We report single crystal high-frequency electron paramagnetic resonance studies of two recently discovered half-integer Fe-7 complexes: [Fe7O3(O2CBu')(9)(mda)(3)(H2O)(3)] (1) and [Fe7O4(O2CPh)(11)(dmem)(2)] (2). The obtained spectra confirm spin S = 5/2 ground states for both complexes. On the basis of detailed frequency and field orientation dependent studies, we find that complex 1 is a single-molecule magnet (uniaxial zero-field-splitting parameter, D < 0) while complex 2 is not (D > 0). The EPR linewidth for complex 1 is considerably narrower in comparison to spectra obtained for other single-molecule magnets, suggesting the possibility of reduced decoherence from nuclear spins (Fe-56 has no nuclear moment). (c) 2006 Elsevier Ltd. All rights reserved.