Nickel(II)–Lanthanide(III) Magnetic Exchange Coupling Influencing Single‐Molecule Magnetic Features in {Ni₂Ln₂} Complexes

Abstract

Four isostructural [Ni2 Ln2 (CH3 CO2 )3 (HL)4 (H2 O)2 ](3+) (Ln(3+) =Dy (1), Tb (2), Ho (3) or Lu (4)) complexes and a dinuclear [NiGd(HL)2 (NO3 )3 ] (5) complex are reported (where HL=2-methoxy-6-[(E)-2'-hydroxymethyl-phenyliminomethyl]-phenolate). For compounds 1-3 and 5, the Ni(2+) ions are ferromagnetically coupled to the respective lanthanide ions. The ferromagnetic coupling in 1 suppresses the quantum tunnelling of magnetisation (QTM), resulting in a rare zero dc field Ni-Dy single-molecule magnet, with an anisotropy barrier Ueff of 19 K.

Synthesis, Crystal Structures, Magnetic Properties, and Fluorescence of Two Heptanuclear CoIII4LnIII3 Compounds (Ln = GdIII, DyIII): Multiple Relaxation Dynamics in the DyIII Analogue

“…The U eff of this system is 230 cm –1 , significantly larger than any SMM of non‐lanthanide metal ions reported so far . Since then, main focus of molecule based magnetic materials was shifted to lanthanide containing systems and, in the last fifteen years, numerous mono/di/oligonuclear SMMs having only 4f metal ions or both 3d and 4f metal ions as the paramagnetic centers, have been reported.…”

“…The family of Schiff base ligands which are obtained on [1+1] condensation of 3‐methoxysalicylaldehyde or 3‐ethoxysalicylaldehyde and an amino alcohol or aminophenol, can stabilize 3d‐4f systems,[26c], , owing to the presence of two types of compartments (as in Scheme ); O(alcohol/phenol)N(imine)O(phenol) and O(ether)O(phenol), where the former is more potential to occupy a 3d metal ion while the latter is more potential to bind a lanthanide. Some Co III Ln III compounds derived from such ligands are also known.…”

Heterometallic 3d–4f single-molecule magnets

“…48 There 49 Two papers report 3d-Er SMMs 62,63 and there are eight 3d-Ho SMMs. 34,57,[64][65][66][67][68]69 All of them display very small energy barriers and no reported blocking temperatures. Some of these are part of families of SMMs, where usually the Dy and Tb analogues display better SMM properties.…”

Synthesis, Crystal Structures, and Magnetic Properties of New Hexanuclear MnIII2LnIII4 Complexes: SMM Behavior of the Terbium(III) Analogue

“…who reported the first lanthanide based SMM, [NBu 4 ][Tb(phthalocyanine) 2 ], with U eff = 230 cm –1 . Since then, numerous 4f[2e], and 3d–4f systems of different nuclearity and dimensionality have been reported with the orientation to improve the key parameter values of the SMMs and also to understand the underlying fundamental aspects. Theoretical models have been proposed and ab initio calculations have been performed to rationalize the magnetic phenomena of the lanthanide based systems.…”

“…Here we describe the results of our investigation focused on hexametallic systems that comprise both anisotropic Mn III ions and anisotropic Ln III ions. It is worth mentioning that the [1+1] condensation products of 3‐methoxysalicylaldehyde and an amino alcohol[18a], , or an aminophenol[27a], have previously been used to isolate 4f and 3d–4f compounds, with a number of them being shown to be SMMs; in fact, it is not overwhelming to say that this family of ligands have occupied a dominating position in 3d–4f and 4f molecular magnetic systems. The interesting aspect of such ligands is that there are two types of pockets, O(phenoxo)N(imine)O(alkoxo) (Pocket I; as in Scheme ) that can bind with a 3d metal ion more potentially, and O(phenoxo)O(methoxy) (Pocket II; as in Scheme ) that preferentially coordinates a 4f metal ion.…”