Polarized Neutron Diffraction to Probe Local Magnetic Anisotropy of a Low‐Spin Fe(III) Complex

Abstract

We have determined by polarized neutron diffraction (PND) the low‐temperature molecular magnetic susceptibility tensor of the anisotropic low‐spin complex PPh4[FeIII(Tp)(CN)3]⋅H2O. We found the existence of a pronounced molecular easy magnetization axis, almost parallel to the C3 pseudo‐axis of the molecule, which also corresponds to a trigonal elongation direction of the octahedral coordination sphere of the FeIII ion. The PND results are coherent with electron paramagnetic resonance (EPR) spectroscopy, magnetometry, and ab initio investigations. Through this particular example, we demonstrate the capabilities of PND to provide a unique, direct, and straightforward picture of the magnetic anisotropy and susceptibility tensors, offering a clear‐cut way to establish magneto‐structural correlations in paramagnetic molecular complexes.

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

“…The main difficulty with these methods is to access the local magnetic anisotropy even when performed on single crystals. We recently showed that polarized neutron diffraction (PND) provides a unique tool to establish precise magneto-structural relationships in mononuclear and dinuclear transition metal complexes of Fe 3+ and Co 2+ ions [9,10]. In this paper we report the study, by angular-resolved magnetometry and polarized neutron diffraction, of the magnetic anisotropy of the [Ni4(L)4(MeOH)4] cluster (Figure 1), so-called [Ni4].…”

Probing the Local Magnetic Structure of the [FeIII(Tp)(CN)3]− Building Block Via Solid‐State NMR Spectroscopy, Polarized Neutron Diffraction, and First‐Principle Calculations

“…[55] In this case, the spin-orbit coupling is treated variationally within the two-component spin-orbit ZORA formalism. The introduction of spin polarization into the g-factor calculations has been tested in previous work [14] and did not converge to the correct ground state (see Ta ble S13 in the Supporting Information). The introduction of spin polarization into the g-factor calculations has been tested in previous work [14] and did not converge to the correct ground state (see Ta ble S13 in the Supporting Information).…”

“…[8] Here, the versatility of the scorpionate ligandsp ermits the adjustment of the steric ande lectronic properties of the precur-sor,a nd hence allows tuning the magnetic properties. [14] In the present work, we have continued to exploret echniques that allow magnetic properties to be probeda tt he local scale. [9][10][11][12][13] Af ew years ago, we undertook af undamental study of the [Fe III (Tp)(CN) 3 ] À building block with the aim of gaining a deeper understanding of its properties by probing the magnetism at the local level.…”

“…Access to cyanidob uilding blocksw ith adjustable electronic properties is also an asset in the designo fm olecular magnetic systems. [14] Indeed, the magnetic properties of molecular materials are mostly determined from bulk measurements that only give access to macroscopic behavior. [7] In particular,w er eported the preparation of the lowspin Fe III building block [Fe III (Tp)(CN) 3 ] À ,i nw hich Tp À is the hydrotris(pyrazolyl)borate scorpionate ligand (see Figure 1).…”

“…(Color scheme:g reen for Fe, bluef or N, grey for C, black for B, and white for H.) The local easy magnetization axis c 1 used in the PND measurements [14] is represented in purple. The advantageo fc ombining theset hree techniques is three-fold.…”