Dy4, Dy5, and Ho2 Complexes of an N3O2 Aminophenol Donor: A Dy5-μ3-Peroxide Single Molecule Magnet

The reactivity of the new flexible potentially pentadentate N3O2 aminophenol ligand H4Lr (2,2'-((pyridine-2,6-diylbis(methylene))bis(azanediyl))diphenol) towards different dysprosium salts and holmium(III) nitrate was investigated. Accordingly, this reactivity seems to greatly depend on the metal ion and salt employed. In this way, the reaction of H4Lr with dysprosium(III) chloride in air leads to the oxo-bridged tetranuclear complex [Dy-4(H2Lr)(3)(Cl)(4)(mu(3)-O)(EtOH)(2)(H2O)(2)]center dot 2EtOH center dot H2O (1 center dot 2EtOH center dot H2O), while the same reaction just changing the chloride salt by the nitrate one renders the peroxo-bridged pentanuclear compound [Dy-5(H2Lr)(2)(H2.5Lr)(2)(NO3)(4)(mu(3)-O-2)(2)]center dot 2H(2)O(2 center dot 2H(2)O), where both peroxo ligands seem to come from the fixation and reduction of atmospheric oxygen. However, if holmium(III) nitrate is used instead of dysprosium(III) nitrate, no evidence of a peroxide ligand is observed, and the dinuclear complex {[Ho-2(H2Lr)(H3Lr)(NO3)(2)(H2O)(2)](NO3)}2.5H2O (3 center dot 2.5H(2)O) is isolated. The three complexes were unequivocally characterized by X-ray diffraction techniques, and their magnetic properties were analyzed. Thus, while the Dy-4 and Ho-2 complexes do not show magnet-like behavior even in the presence of an external magnetic field, 2 center dot 2H(2)O is a single molecule magnet, with an U-eff barrier of 61.2 K (43.2 cm(-1)). This is the first homonuclear lanthanoid peroxide SMM, which also shows the highest barrier among the reported 4f/3d peroxide zero field SMMs to date.

Automated summary

The reactivity of the N3O2 aminophenol ligand H4Lr towards different dysprosium salts and holmium(III) nitrate was studied. The reaction outcomes were found to depend on the metal ion and salt used. The resulting complexes were characterized and their magnetic properties were analyzed. One of the complexes showed single molecule magnet behavior with the highest barrier reported to date for peroxide zero field single molecule magnets.