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

Abstract: We report single crystal high-frequency electron paramagnetic resonance studies of two recently discovered half-integer Fe7 complexes: [Fe7O3(O2CBu t )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 (56Fe has no nuclear moment). [Copyright &y& Elsevier]