Two planar tetranuclear dysprosium(III) complexes, [DY4(mu(3)-OH)(2)-(hmmpH)(2)(hMMP)(2)(Cl)(4) center dot 3MeCN center dot MeOH (1) and [DY4(mu(3)-OH)(2)-(hmmpH)(2)(hMMP)(2)(N-3)(4)] center dot 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.