Three dinuclear lanthanide(iii) compounds of a polydentate Schiff baseligand: Slow magnetic relaxation behaviour of the DyIII derivative

Abstract

The initial employment of N₁,N₂,N₃,N₄-tri(3-methoxysalicylidene) triethylenetetraamine ligand (H₃L, Scheme 1) in lanthanide coordination chemistry for single molecule magnets has yielded a new family of dinuclear Ln^III₂ compounds with the general formula of [Ln₂(L)₂]·nCH₃CN (Ln = Gd (1), Tb (2) with n = 0, Ln = Dy (3) with n = 4). These three complexes have been structurally and magnetically characterized. The structural analyses reveal that they are isomorphous dinuclear complexes where the Ln₂ entities were encapsulated by two polydentate Schiff base ligands. Variable-temperature magnetic susceptibility studies indicate the presence of dominant antiferromagnetic interactions in complexes 2 and 3, whereas complex 1 containing isotropic Gd ions allows the quantification of the antiferromagnetic interaction with J_Gd–Gd = −0.041 cm⁻¹. Dynamic measurements reveal that 3 displays single-molecule magnet behaviour with an activation energy barrier Δ = 18.9 K and pre-exponential factor τ₀ = 3.92 × 10⁻⁶ s, while 1 and 2 do not show any out-of-phase ac susceptibility signals.