Anion-perturbed magnetic slow relaxation in planar {Dy4} clusters

Two planar tetranuclear dysprosium(III) complexes, Dy(4)(mu(3)-OH)(2)(hmmpH)(2)(hmmp)(2)(Cl)(4)].3MeCN.MeOH (1) and Dy(4)(mu(3)-OH)(2)(hmmpH)(2)(hmmp)(2)(N(3))(4)].4MeOH (2) {hmmpH(2) = 2-(2-hydroxyethylimino)methyl]-6-methoxyphenol}, which exhibit an anion-dependent magnetic slow relaxation behavior, have been synthesized by in situ condensation of o-vanillin and 2-aminoethanol. The higher energy barrier observed in 2 could be the result of a more favorable crystal field and/or orientations of single-ion easy axes of magnetization of the Dy(III) ions.