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Chemistry Eur. J. [POMAM / LCQ]

mai 12 2020

Abstract :

Previously reported ferromagnetic triangles (NnBu4)2[Cu3(μ‐Cl)2(μ‐4‐NO2‐pz)3Cl3] (1), (PPN)2[Cu3(μ‐Cl)2(μ‐pz)3Cl3](2), (bmim)2[Cu3(μ‐Cl)2(μ‐pz)3Cl3] (3) and newly reported (PPh4)2[Cu3(μ‐Cl)2(μ‐4‐Ph‐pz)3Cl3] (4) were studied by magnetometry, Electron Paramagnetic Resonance (EPR) spectroscopy and ab initio calculations to assess the origins of their ferromagnetism and of the magnetic anisotropy of their ground S = 3/2 state (PPN+ = bis(triphenylphosphine)iminium, bmim+ = 1‐butyl‐3‐methylbenzimidazolium). Ab initio studies revealed the dz2 character of the magnetic orbitals of the compressed trigonal bipyramidal copper(II) ions. Ferromagnetic interactions were attributed to weak orbital overlap via the pyrazolate bridges. From the wavefunctions expansions, the ratios of the magnetic couplings was determined, which was indeterminate by magnetic susceptometry. Single‐crystal EPR studies of 1 were carried out to extend the spin Hamiltonian with terms which induce zero‐field splitting (zfs), namely dipolar interactions, anisotropic exchange and Dzyaloshinskii‐Moriya interactions (DMI). The data were treated through both a giant‐spin model and through a multispin exchange‐coupled model. The latter indicated that ~62% of the zfs is due to anisotropic and ~38% due to dipolar interactions. The powder EPR data of all complexes were fitted to a simplified form of the multispin model and the anisotropic and dipolar contributions to the ground state zfs were estimated.

Reference :

Logesh Mathivatanan, Guillaume Rogez, Nadia Ben Amor, Vincent Robert, Raphael G. Raptis, Athanassios Boudalis

Origin of ferromagnetism and magnetic anisotropy in a family of copper(II) triangles

Chem. Eur. J, First published: 28 April 2020, DOI : https://doi.org/10.1002/chem.202001028 


Contact chercheur :

Athanassios K. Boudalis (https://pomam.chimie.unistra.fr/aboudalis/), POMAM, Institut de Chimie (UMR 7177).