Magnetic Exchange Effects in {CrIII2DyIII2} Single Molecule Magnets Containing Alcoholamine Ligands

Abstract

The synthesis and magnetic characterisation of four new heterometallic {CrIII2DyIII2} complexes 2–5 are described. The present work follows on from a recently isolated complex [CrIII2DyIII2(OMe)2(O2CPh)4(mdea)2(NO3)2] (1) (mdeaH2 = N-methyldiethanolamine), which displayed impressive single molecule magnet (SMM) properties, notably highly coercive magnetic hysteresis loops below 3.5 K. Compounds 1–5 all display a planar butterfly type metallic core arrangement, with the DyIII ions occupying the central body positions and the CrIII ion the outer wing positions. The core is stabilized by the amine–diolate, and carboxylate bridging ligands. Variation of the amine–diolate ligand resulted in several structural analogues which maintain the same metallic core, but differ from the parent 1 in the outer ligand coordination environment. Magnetic studies reveal complexes 2–5 also display SMM behaviour, unambiguously confirmed via low temperature magnetic hysteresis loops, each displaying wide coercive fields, a rare occurrence for lanthanoid-based SMMs.