Experimental and theoretical exploration of magnetic exchange interactions and single-molecule magnetic behaviour of bis(η¹:η²:μ₂-carboxylate)GdIII2/DyIII2 systems

Abstract

The present report deals with the syntheses, crystal structures, dc/ac magnetic properties and DFT/ab initio CASSCF calculations of two isomorphous bis(η1:η2:μ2-acetate)GdIII2/DyIII2 compounds of the formula [LnIII2L2(acetate)4(MeOH)2] (1, Ln = Gd; 2, Ln = Dy), where HL is (E)-N'-(3-ethoxysalicylidene)acetohydrazide. The two lanthanide(iii) centres in each compound are symmetry-related owing to the presence of an inversion centre. Both compounds exhibit intramolecular ferromagnetic exchange interactions. The DyIII2 analogue is a single-molecule magnet (SMM) with Ueff = 52.8 cm-1 and τ0 = 1.52 × 10-6 s. DFT calculations for 1 and ab initio calculations for 2 also reveal ferromagnetic interactions. Ab initio calculations of the SMM behaviour of 2 and two other reported and structurally related compounds reveal the importance of the weak exchange interaction present between the two DyIII ions, and a relaxation mechanism has been developed to take into account the magnetic exchange interaction and to rationalize the observed difference in the Ueff values.

Two Dy(III) Single-Molecule Magnets with Their Performance Tuned by Schiff Base Ligands

“…The coordination sites of Dy­(III) for 1 are occupied by one N and seven O atoms from one methanol, one NO 3 – , and two (HL 1 ) 2– ligands, forming a bicapped trigonal prism (Figure S6). The bond lengths of Dy­(III)-O/N are 2.231(2)–2.535(17) Å, agreeing well with the reported values in literatures. − (HL 1 ) 2– acts as a μ 2 -bridge (Figure S7) using its O phenolic , N imino , and one O alkoxy atoms to chelate one of the Dy­(III) ions and using its two O alkoxy atoms to chelate the other Dy­(III) ion. Dy1 and Dy1A in 1 are thus linked by two (HL 1 ) 2– ligands through their two O alkoxy atoms to form a dinuclear skeleton (Figure ) with the Dy–O–Dy angle and the Dy···Dy distance of 110.72(9)° and 3.7073(4) Å, respectively, which are similar to the reported values. ,− …”

“…All of these features confirm that both 1 and 2 are SMMs. 47,52,64 To explore the relaxation processes of 1 and 2, their Cole− Cole diagrams (χ′′ vs χ′ isothermal curves) were plotted from their frequency-dependent ac susceptibilities (Figure 6d−f). The profiles of these Cole−Cole diagrams for both titled complexes are near-semicircle.…”

Homochiral Ferromagnetic Coupling Dy2 Single-Molecule Magnets with Strong Magneto-Optical Faraday Effects at Room Temperature

“…The simplest one is the lanthanide (III) dinuclear SMM. The ferromagnetic coupling strategy may make the magnetic orientation of the two lanthanide (III) ions uniform, but it is still a very difficult task. − The main reason is that the 4f electrons from different lanthanide (III) ions are not easily magnetically exchanged with each other; even if this magnetic exchange occurs, it is usually a weak antiferromagnetic interaction.…”

In silico design to enhance the barrier height for magnetization reversal in Dy(iii) sandwich complexes by stitching them under the umbrella of corannulene

“…15 This methodology has been established as a reliable tool to predict g-tensors and energies of low lying states for 4f, 3d-4f, and 4f-4f complexes. 11,19,20,30,[33][34][35][36][37][38][39][40] We have computed eight low lying Kramer's Doublets (KDs) corresponding to 6 H 15/2 state. For all these complexes, the eight low-lying KDs lie within an energy span of 717 -1092 cm -1 (see Table 1).…”