Hydrazone‐Ligand‐Based Homodinuclear Lanthanide Complexes: Synthesis, Structure, and Magnetism

Abstract

A series of dinuclear lanthanide complexes, [Dy2(LH)2(µ2‐Piv‐κ2O,O′)2(NO3‐κ2O,O′)2] (1), [Tb2(LH)2(µ2‐Piv‐κ2O,O′)2(NO3‐κ2O,O′)2] (2), [Gd2(LH)2(µ2‐Piv‐κ2O,O′)2(NO3‐κ2O,O′)2] (3), and [Ho2(LH)2(µ2‐Piv‐κ2O,O′)2(NO3‐κ2O,O′)2] (4) have been synthesized by the reaction of Ln(NO3)3·nH2O with the multidentate hydrazone‐based Schiff‐base ligand, N′‐(2‐hydroxy‐3‐methoxybenzylidene)acetohydrazide (LH2) in the presence of pivalic acid. X‐ray crystallography data reveals that 1–4 are isostructural, neutral, and contain two mono‐deprotonated ligands, two pivalates, and two chelated nitrates. Within the dinuclear assembly, the two lanthanides are bridged by two phenolate and two pivalate oxygens. Each of the two lanthanide ions is nine‐coordinated and possesses a distorted monocapped square‐antiprism geometry. Detailed magnetochemical analysis revealed the presence of weak antiferromagnetic coupling at low temperature for all complexes. The DyIII analogue displayed SMM behavior in the absence of a dc field with two relaxation domains in which the thermally activated domain exhibits an energy barrier of 40 K and relaxation time of 6.5 × 10–5 s.

Magnetic Slow Relaxation in a Metal–Organic Framework Made of Chains of Ferromagnetically Coupled Single‐Molecule Magnets

“…Four oxygen atoms (O1, O2, O4, O6) bind only one Dy III ion (μ 1 mode) and four oxygen atoms (O3, O3a, O5, O5a) bind two Dy III ions (μ 2 mode; Figure and Table S1 in the Supporting Information). From the magnetic point of view, this last coordination mode is expected to transmit a sizeable magnetic interaction between the Dy III ions , , . The Dy III ion presents a muffin‐like coordination polyhedron ( C s ) (Figure , Table S2 in the Supporting Information).…”

Homometallic DyIII Complexes of Varying Nuclearity from 2 to 21: Synthesis, Structure, and Magnetism

“…We have been involved in the design and utilization of various types of ligand families for the preparation of 3d/4f–, and 4f–,,, complexes. From our experience,, and those of others we have observed that flexible ligands that have multiple options to bind to a metal ion are often suitable to generate polynuclear complexes. Among the ligands that we have investigated, aroyl hydrazone ligands have been found to possess the following beneficial features.…”

Homodinuclear {LnIII2} (LnIII = GdIII, TbIII, HoIII, and DyIII) Complexes: Field‐Induced SMM Behavior of the DyIII and TbIII Analogues

“…We have been utilizing multidentate hydrazone ligands, for some time, to assemble lanthanide complexes . In this context, we wished to explore a o ‐vanillin‐supported multidentate ligand, N′ ‐(2‐hydroxy‐3‐methoxy‐5‐nitrobenzylidene)‐2‐(hydroxyamino) propanehydrazide (H 3 L) to prepare dinuclear Ln III complexes.…”

“…[14] We have been utilizing multidentate hydrazone ligands, for some time, to assemble lanthanide complexes. [29][30][31] In this context, we wished to explore a o-vanillin-supported multidentate ligand, N′-(2-hydroxy-3-methoxy-5-nitrobenzylidene)-2-(hydroxyamino) propanehydrazide (H 3 L) to prepare dinuclear Ln III complexes. Based on our previous understanding of such ligand systems we intuited that keto-enol tautomerism would allow H 3 L to be present in an enol form and when de-protonated the enolate oxygen can be profitably used to bridge two lanthanide ions.…”