Three dinuclear lanthanide(iii) compounds of a polydentate Schiff base ligand: 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 LnIII2 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 JGd–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.