[LnIII–MnII–LnIII] heterometallic compounds: rare linear SMMs with divalent manganese ions†
Abstract
The reaction of Mn(OAc)2·4H2O and Ln(NO3)3·6H2O with N-(2-aminopropyl)-2-hydroxybenzamide and salicylic aldehyde in methanol/methylene dichloride produces yellow crystals of Ln2Mn(C7H5O2)8 (Ln = Gd (1), Tb (2), Dy (3), Ho (4) and Er (5)), in the presence of triethylamine. Three metal ions are connected by six μ2-phenolate oxygen atoms of six salicylic aldehyde ligands, resulting in perfect linear [LnIII–MnII–LnIII] structures. Magnetic studies of these complexes have been performed and AC susceptibility measurements show the presence of a temperature-dependent out-of-phase ac signal for complexes 2 and 3 indicating single-molecule magnet (SMM) behavior. The DyIII2MnII compound shows double relaxation pathways which may originate from the single ion behavior of individual DyIII ions and the weak coupling between DyIII and MnII ions, respectively. The Ueff of 92.4(2) K is a relatively high value among 3d–4f SMMs. Moreover, complexes 2 and 3 represent the first linear Mn–Ln SMMs containing only divalent manganese ions as far as we know. The result suggests the positive effects of magnetic coupling to enhance their SMM behavior, presenting a promising strategy for constructing efficient heterometallic SMMs.