Single-Molecule-Magnet Fe^II₄Fe^III₂ and Antiferromagnetic Fe^III₄ Coordination Clusters

Abstract

Supported by endogenous (part of the ligand, in-built) phenoxo bridges provided by the ligand 2,6-bis­[{{(5-bromo-2-hydroxybenzyl)}­{(2-(pyridylethyl)}­amino}­methyl]-4-methylphenol) (H3L), in its deprotonated form, exogenous (not part of the ligand, externally added or generated) oxo-/hydroxo- and acetato-bridged [FeII 4FeIII 2(O)2(O2CMe)4(L)2]·4Et2O (1) and [FeIII 4(OH)2(O2CMe)3(L)2]­(ClO4)·3MeCN·2H2O (2) coordination clusters have been synthesized and structurally characterized. Complexes 1 and 2 have μ4-O and μ3-OH bridges, respectively. Magnetic studies on 1 reveal slow magnetic relaxation below 2 K. Both in-phase (χ′ M) and out-of-phase (χ″M) magnetic susceptibility were found to be frequency dependent. This is typical of a single-molecule magnet (SMM) with τ0 = 1.9(2) × 10–7 s–1 and E a = 5.1(3) cm–1. Assuming that E a corresponds to the energy splitting of the ground spin state (S = 2) by the zero-filed-splitting (zfs), E a = 4|D| (D is the axial zfs parameter), D ≈ – 1.3 cm–1 could be estimated. For 2, three types of magnetic interactions are observed: J A = −56.5(3), J B = −71.6(4), and J C = +4.5(2) cm–1. Considering the observed structural parameters, the magnetic behavior for both of the coordination clusters 1 and 2 has been rationalized.

Magnetic Properties of High-Nuclearity Fex-oxo (x = 7, 22, 24) Clusters Analyzed by a Multipronged Experimental, Computational, and Magnetostructural Correlation Approach

“…Dinuclear Fe III complexes have served as both model systems to understand magnetic exchange couplings via magnetostructural correlations (MSCs) as well as synthetic analogues of di-iron biomolecules such as ribonucleotide reductase, , hemerythrin, and the soluble methane monooxygenase, , among others . Higher-nuclearity Fe III /oxo clusters are likewise highly coveted as potential models of intermediates in the growth of nanoscale Fe III /O/OH units during the loading of the ferritin protein, as well as new magnetic molecules and single-molecule magnets (SMMs). − …”

Li4Ru2OCl10·10H2O: crystal structure, magnetic properties and bonding interactions in ruthenium-oxo complexes

“…Most oxo-di-metallic molecular clusters have been well studied for their catalytic properties and medicinal applications (Zimmermann et al, 2018;Arii et al, 2000;Kurtz, 1990;Engelmann et al, 2016). However, limited research has been conducted to understand their magnetic properties (Sessoli et al, 1993;Singh & Rajaraman, 2019;Lang et al, 2018;Barman et al, 2019). Although magneto-structural correlations largely differ from system to system, up-to-date studies reveal that the bridging bond angle is a crucial parameter in this context.…”