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Keywords:

  • carboxylate ligands;
  • EPR spectroscopy;
  • magnetic properties;
  • Ni-cubanes;
  • steric hindrance

Abstract

Using two kinds of carboxylate ligands with small but significant differences in steric size, symmetric and asymmetric FeII and NiII cubanes have been synthesized in a controlled fashion. Fast sweeping pulsed field measurements showed magnetization hysteresis loops for two cubane-type molecular complexes, [Ni4(μ-OMe)4(O2CAr4F-Ph)4(HOMe)8] and [Ni4(μ-OMe)4(O2CArTol)4(HOMe)6], thus suggesting single-molecule magnet behavior. To differentiate the magnetic properties between the symmetric and asymmetric cubanes, detailed electron paramagnetic resonance (EPR) measurements were performed. From the EPR data, taken at various frequencies and temperatures, zero-field splitting parameters D, E, and other higher-order parameters for both cubane samples were extracted. Compared to the symmetric Ni-cubane, the asymmetric one shows an increase in the D and E values by about 20 %, thereby suggesting structural engineering effects on the magnetic properties. By using the magnetic parameters determined by EPR, a static magnetization curve at 2 K and a temperature dependence of the magnetic susceptibility were simulated. A good agreement between theoretical and experimental data confirms the validity of the values obtained from EPR measurements.

Featured Compounds

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Compound 1
Molecular Weight:1788.6362
Molecular Formula:C95H108Ni4O19
InChIKey:GLOQBNLTVWXADK-UHFFFAOYSA-J
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Compound 2
Molecular Weight:1884.431
Molecular Formula:C89H92F8Ni4O21
InChIKey:UFICZDWMKQOACB-UHFFFAOYSA-J
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