Pentanuclear [2.2] spirocyclic lanthanide(III) complexes: slow magnetic relaxation of the Dy-III analogue

Abstract

The reaction of LnCl3·6H2O (Ln = Dy3+, Tb3+ and Ho3+) with the multisite coordinating ligand N′-(2-hydroxy-3-(hydroxymethyl)-5-methylbenzylidene)acetohydrazide (LH3) in the presence of pivalic acid (PivH) leads to the formation of three isostructural homometallic pentanuclear complexes, [Dy5(LH)4(η1-Piv)(η2-Piv)3(μ2-η2η1Piv)2(H2O)]·Cl·9·5H2O·5MeOH (1), [Tb5(LH)4(η1-Piv)(η2-Piv)3(μ2-η2η1Piv)2(H2O)]·Cl·10.5H2O·2MeOH·2CHCl3 (2) and [Ho5(LH)4(η1-Piv)(η2-Piv)3(μ2-η2η1Piv)2(H2O)]·Cl·14.5H2O·2CHCl3 (3). 1-3 are monocationic and are comprised of four doubly deprotonated [LH]2- ligands along with six pivalate ions. These complexes possess a [2.2] spirocyclic topology formed by the fusion of two triangles of LnIII ions at a common vertex. The magneto chemical analysis reveals the presence of antiferromagnetic exchange interactions at low temperature, and the DyIII complex 1 gives an out-of-phase signal with a small curvature in alternating current (ac) magnetic susceptibility measurement. Application of a 3000 G static field during ac measurement intensifies the signals, revealing a second slow relaxation process in the DyIII analogue. © The Royal Society of Chemistry.