A diferrous single-molecule magnet

作者：Boudalis Athanassios K^*; Sanakis Yiannis; Clemente Juan Juan Modesto; Mari Alain; Tuchagues Jean Pierre

来源：European Journal of Inorganic Chemistry, 2007, (17): 2409-2415.

DOI：10.1002/ejic.200700203

• single-molecule studies
• cluster compounds
• magnetic properties
• iron

The diferrous complex [Fe-2(acpypentO)(NCO)(3)] (1), (acpypentO(-) = the anion of 1,5-bis[2-pyridyl(1-ethylimino)]-pentane-3-ol) was studied by spectroscopic (dual-mode X-band EPR and Fe-57-Mossbauer) and magnetic (AC magnetic susceptibility) techniques. Complex 1 (A. K. Boudalis et al., Inorg. Chem. 2004, 43, 1574) was previously shown to exhibit an intramolecular ferromagnetic coupling with important single-ion anisotropies with marked differences in the singleion electronic parameters of the two iron sites. In this contribution, additional studies are carried out to probe its dynamic magnetic properties. Mossbauer spectra recorded at liquid helium temperatures indicate slow paramagnetic relaxation and a ground state of the system characterized by a non-Kramers doublet with an Ising-type anisotropy, a condition which favours single-molecule magnet (SNIM) behaviour. A frequency-dependent out-of-phase signal observed below 3 K in AC susceptibility measurements is in line with such a picture. The out-of-phase signal, however, is relatively weak in comparison with the in-phase signal. Dual mode X-band EPR spectroscopy revealed characteristic signals, the analysis of which suggests inhomogeneities in the system. For some molecules, the splitting Delta(0) of the non-Kramers ground doublet is vanishingly small, which gives rise to out-of-phase signals in AC susceptibility measurements and magnetically split Mossbauer spectra in the absence of external magnetic fields. Other molecules, however, are characterized by a nonnegligible Delta(0), which gives rise to the dual mode X-band EPR signals. For these molecules the magnetic relaxation is fast.

• 出版日期2007-6