Pentanuclear Heterometallic {Ni₂Ln₃} (Ln = Gd, Dy, Tb, Ho) Assemblies. Single-Molecule Magnet Behavior and Multistep Relaxation in the Dysprosium Derivative

Abstract

The reaction between Ln(III) chloride and NiCl2·4H2O salts in presence of a multidentate sterically unencumbered ligand, (E)-2,2'-(2-hydroxy-3-((2-hydroxyphenylimino)methyl)-5-methylbenzylazanediyl)diethanol (LH4) leads to the synthesis of four isostructural pentanuclear hetereometallic complexes [Ni2Dy3(LH)4]Cl (1), [Ni2Gd3(LH)4]Cl (2), [Ni2Tb3(LH)3(LH2)]Cl2 (3), [Ni2 Ho3 (LH)3 (LH2)]Cl2 (4) with unprecedented topology. Here the two compounds 1 are 2 are monocationic and crystallize in chiral space group, P2(1)2(1)2(1) whereas compounds 3 and 4 are dicationic and crystallize in achiral space group P2(1)/n. The total metal framework, {Ni2Ln3} unit is held by four triply deprotonated ligands [LH](3-) in 1 and 2 whereas in case of 3 and 4 three triply deprotonated [LH](3-) and one doubly deprotonated [LH2](2-) ligands are involved. In these complexes both the lanthanide ions and the nickel(II) ions are doubly bridged and the bridging is composed of oxygen atoms derived from either phenolate or ethoxide groups. The analysis of SQUID measurements reveal a high magnetic ground state and a slow relaxation of the magnetization with two relaxation regimes for 1. For the thermally activated regime we found an effective energy barrier of U(eff) = 85 K. Micro Hall probe loop measurements directly proof the single-molecule magnet (SMM) nature of 1 with a blocking temperature of T(B) = 3 K and an open hysteresis for sweep rates faster than 50 mT/s.

Pentanuclear Spirocyclic Ni4Ln Derivatives: Field Induced Slow Magnetic Relaxation in the Dysprosium and Erbium Analogues

“…From the knowledge base of Ni–Ln compounds, synthetic methods offer a variety of topology with different levels of control in the design. To the best of our knowledge, only six pentanuclear Ni–Ln heteronuclear complexes, (Figure ) are found whose detailed magnetic analysis has been done. Although the spirocyclic core is well known in pure 4f based compounds, the case of coordination compounds based on 3d‐4f systems, it is scare.…”

Heterometallic Pentanuclear [Ni4Ln] (LnIII = Gd, Tb, Dy, Ho) Complexes: Accidental Orthogonality Leading to Ferromagnetic Interactions

“…Our research group has been investigating the metalation behavior of the phosphorus‐supported tris‐hydrazone ligand, S=P[N(Me)N=CH‐C 6 H 3 ‐2‐OH‐3‐OMe] 3 (LH 3 ) with transition‐metal/lanthanide ions and has found that 3d homotrimetallic5 and 3d‐4f heterotrimetallic6 compounds can be readily prepared by using this family of ligands, many of which are SMMs. Also, through the use of compartmental ligands we have assembled [Cu II Ln III ],7a [Cu II 5 Ln III 2 ],7b [Ni II 2 Ln III 3 ],7c [Zn II /Ln III ],7d [Co II 2 Ln III ],7e and [Mn III 2 Ln III 2 ]7f complexes. Recently, the use of 6‐formyl‐2‐(hydroxymethyl)‐4‐methylphenol (LH 2 ) allowed us to assemble the first examples of heterometallic pentanuclear Co II 4 Ln III complexes 8.…”

A family of nickel–lanthanide heterometallic dinuclear complexes derived from a chiral Schiff-base ligand exhibiting single-molecule magnet behaviors

“…As aforementioned, complexes 6 and 7 display the field-induced SMM behaviors. Most of Ni II -Ln III complexes behaving as SMMs contain paramagnetic Ni II ions, however, the Ni II -Ln III system that exhibits the highest energy barrier ever found is a {Ni 3 Dy 2 } cluster complex [31] in which the Ni II ions, as our compounds, are diamagnetic. Compared with the similar works using achiral Schiff-base ligands [23a], we investigate the ac properties of target complexes in details.…”