Search

Over the past decade, lanthanide compounds have become of increasing interest in the field of Single Molecule Magnets (SMMs) due to the large inherent anisotropy of the metal ions. Heavy lanthanide metal systems, in particular those containing the dysprosium(iii) ion, have been extensively employed to direct the formation of a series of SMMs. Although remarkable progress is being made regarding the synthesis and characterization of lanthanide-based SMMs, the understanding and control of the relaxation dynamics of strongly anisotropic systems represents a formidable challenge, since the dynamic behaviour of lanthanide-based SMMs is significantly more complex than that of transition metal systems. This perspective paper describes illustrative examples of pure dysprosium(iii)-based SMMs, published during the past three years, showing new and fascinating phenomena in terms of magnetic relaxation, aiming at shedding light on the features relevant to modulating relaxation dynamics of polynuclear lanthanide SMMs. [ABSTRACT FROM AUTHOR]

Two dinuclear triple-stranded helicates [Ln2L3]3+(Ln = Dy and Tb) obtained viaself-assembly from the ligand HL (2,6-diformyl-4-methylphenol di(benzoylhydrazone)) and lanthanide perchlorate have been synthesized and characterized. The crystal structural analysis demonstrates that three ligand strands wrap around a pseudo-threefold axis defined by the two metal ions, leading to a ‘meso’-relation between the right- (Δ) and left-hand (Λ) configurations of [Ln2L3]3+in the crystal. Each LnIIIion is coordinated by nine donor atoms in a distorted tricapped trigonal-prismatic arrangement. Alternating current (ac) susceptibility measurements of [Dy2L3]3+reveal a frequency-dependent out-of-phase signal under a 700 Oe dc field, indicating the onset of the slow relaxation of magnetization with a roughly estimated activation energy of ∼5 K and τ0of 10−7s. [ABSTRACT FROM AUTHOR]

The reaction of Dy(NO3)3·6H2O with the ligand 2-((1-hydroxybutan-2-ylimino)methyl)phenol (H2L, Scheme 1) generates the nonanuclear compound [Dy9L8(μ3-OH)8(μ4-OH)2(CH3OH)8](OH)(CH3OH)3(Dy9), whose single-crystal X-ray structure reveals the presence of two square pyramidal pentanuclear units assembled viathe apical metal center. The square pyramidal core of a previously reported [Dy5(μ4-OH)(μ3-OH)4(μ-η2-Ph2acac)4(η2-Ph2acac)6] (Dy5; Ph2acac = dibenzoylmethanide), is structurally related to those herein described; however, the magnetic properties of Dy9and Dy5are drastically different. Indeed, Dy5shows slow relaxation of magnetization while no out-of-phase ac signal is noticed for Dy9. The underlying mechanism is not clear due to the complexity of such systems; however, the different anisotropy of the respective structures, which is dictated by the combination of the metal topology, the ligands involved and the structural parameters of the molecule, is mostly responsible for the distinctive relaxation dynamics observed. [ABSTRACT FROM AUTHOR]

Reactions of Ln(iii) acetate (Ln = Pr and Nd) and a polydentate Schiff-base in a mixture of methanol and acetonitrile resulted in the unprecedented assembly of novel Ln10aggregates containing two Ln5pentagons templated by μ5-CO32−, introduced viaspontaneous fixation of atmospheric carbon dioxide. Magnetic analysis using an expression including the ligand field effects and molecular field approximation indicates weak antiferromagnetic coupling between the metal ions. This synthetic approach may represent a promising new route toward the design of new lanthanide clusters and novel multifunctional materials. [ABSTRACT FROM AUTHOR]