Mapping the Magnetic Anisotropy inside a Ni4 Cubane Spin Cluster Using Polarized Neutron Diffraction

Abstract

Abstract:In this publication, we report on the study of the magnetic anisotropy of the cubane type tetranuclear cluster of Ni(II), [Ni 4 (L) 4 (MeOH) 4 ] (H 2 L = salicylidene-2-ethanolamine; MeOH = methanol), by the means of angular-resolved magnetometry and polarized neutron diffraction (PND). We show that better than other usual characterization techniques-such as electron paramagnetic resonance spectroscopy (EPR) or SQUID magnetometry-only PND enables the full determination of the local magnetic susceptibility tensor of the tetranuclear cluster and those of the individual Ni(II) ions and the antiferromagnetic pairs they form. This allows highlighting that, among the two antiferromagnetic pairs in the cluster, one has a stronger easy-axis type anisotropy. This distinctive feature can only be revealed by PND measurements, stressing the remarkable insights that they can bring to the understanding of the magnetic properties of transition metals clusters.

Synthesis, Magnetic and High-Field EPR Investigation of Two Tetranuclear NiII-Based Complexes

“…We note that the absolute values are also within the range observed for other tetranuclear ferromagnetically coupled Ni II -based compounds. 7,37,30 To corroborate the results from the HFEPR measurements, isothermal magnetization was measured as a function of applied magnetic field for both compounds (Figure S6). Since it was determined that the spin ground state corresponds to S T = 4, the magnetic data were fitted with the same giant spin Hamiltonian as used to simulate the HFEPR spectra (eq 3).…”

“…These relatively high χ M T maxima were observed for similar Ni II -based cubanes. 10,37 Subsequently, upon lowering the temperature, χ M T decreases due to antiferromagnetic intermolecular interactions and/or magnetic anisotropy (ZFS) associated with the Ni II…”

Magnetic anisotropies of Ho(iii) and Dy(iii) single-molecule magnets experimentally determined via polarized neutron diffraction

“…This technique can then be used, by mapping the magnetic susceptibility tensor of individual atoms in a molecule, to determine the magnetic anisotropy of the molecule directly from an experiment. [30][31][32][33] Flipping ratio data, which suppress the need for deuterated samples, were collected on the 6T2-diffractometer of the Laboratorie Léon Brillouin (LLB) on the Orpheé reactor. 43 Diffraction data was collected for three (1) and four (2) crystal orientations.…”

“…While both AC and DC magnetic measurements are standard techniques in molecular magnetism, the use of PND to study the magnetic anisotropy of molecular magnets is extremely rare, with only a handful of published studies in the literature. [30][31][32][33][34][35][36] Thus, this work represents the first comparative study of two lanthanide-ions in identical crystal fields using the PND technique.…”

Formation of Tetranuclear Nickel(II) Complexes with Schiff-Bases: Crystal Structures and Magnetic Properties

“…For the latter, attention has recently been attracted for testing these tetrametallic molecular systems in applications as water oxidation catalysts [31][32][33] or for electrocatalytic methanol oxidation reactions [34]. In the field of molecular magnetism, cubane-like clusters have for long been in the center of magnetic studies [8][9][10][11][12][13][14][15][16][17][18][19][22][23][24][25][26][27][28][29][30][35][36][37][38][39][40], while deliberately and systematically looking for magnetostructural correlations. Thereby, one can note that even slight structural rearrangements of the cubane core, e.g., caused by exchange of coordinated solvent or loss of lattice solvent can lead to drastic changes of the magnetic properties.…”