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Lanthanide Single‐Molecule Magnets are fascinating objects that break magnetic performance records with observable magnetic bistability at the boiling temperature of liquid nitrogen, paving the way for potential applications in high‐density data storage. The switching of lanthanide SMM has been successfully achieved using several external stimuli such as redox reaction, pH titration, light irradiation or solvation/desolvation thanks to the high sensitivity of the magnetic anisotropy to any structural change in the lanthanide surrounding. Nevertheless, the use of applied high pressure as an external stimulus is largely underused, especially considering that it can be combined with high pressure X‐ray diffraction to establish a complementary structure‐property relationship. This Concept article summarizes the few relevant examples of investigations of lanthanide SMMs under applied high pressure, provides conclusions on the effect of such stimulus on molecular structures and magnetic anisotropy, and finally draws perspective on the future development of magnetic measurements under applied pressure. [ABSTRACT FROM AUTHOR]

The combination of physical properties sensitive to molecular chirality in a single system allows the observation of fascinating phenomena such as magneto‐chiral dichroism (MChD) and circularly polarized luminescence (CPL) having potential applications for optical data readout and display technology. Homochiral monodimensional coordination polymers of YbIII were designed from a 2,15‐bis‐ethynyl‐hexahelicenic scaffold decorated with two terminal 4‐pyridyl units. Thanks to the coordination of the chiral organic chromophore to Yb(hfac)3 units (hfac−=1,1,1,5,5,5‐hexafluoroacetylaconate), efficient NIR‐CPL activity is observed. Moreover, the specific crystal field around the YbIII induces a strong magnetic anisotropy which leads to a single‐molecule magnet (SMM) behaviour and a remarkable room temperature MChD. The MChD‐structural correlation is supported by computational investigations. [ABSTRACT FROM AUTHOR]

The effects of isotopic enrichment and magnetic dilution have been investigated in a heterobimetallic complex of formula [Zn2L2ADyCl3]·2H2O (ADyZn2) (A = 162 and 163) presenting slow relaxation of the magnetization. Isotopic substitution for 162Dy (I = 0) and 163Dy (I = 5/2) leads to a shift in the relaxation times depending on the suppression or enhancement of the hyperfine interactions. The release of the dipolar interactions through magnetic dilution in a Y(III)-based matrix enhances the slow relaxation of the magnetization and the visibility of the nuclear spin effect. A comparison of the hysteresis loop at 0.5 K for bulk and diluted analogues of pure isotopically enriched complexes suggested a role of the nuclear spin in the interaction between the active system and the matrix. [ABSTRACT FROM AUTHOR]

We report here a dinuclear DyIII iodine-bridged single-molecule magnet self-assembled by cis/trans coordination chemistry that displays a large anisotropy barrier of ca. 1300 K and a hysteresis opening temperature of 16 K. High temperature quantum tunnelling of magnetization is observed up to 56 K in zero-field and explained by the combination of the large anisotropy barrier and the local transverse field at the trans site. The results provide a model for thorough understanding of the effect of electronic structure on the magnetic behavior of lanthanide complexes. [ABSTRACT FROM AUTHOR]

An alternative strategy for the synthesis of terpyridine based switchable molecular tweezers has been developed to incorporate anisotropic Mn(III)–salphen complexes. The free ligand was synthesized using a building block strategy based on Sonogashira coupling reactions and was then selectively metalated with manganese in a last step. The conformation of the tweezers was switched from an open 'W' shaped form to a closed 'U' form by Zn(II) coordination to the terpyridine unit bringing the two Mn–salphen moieties in close spatial proximity as confirmed by X-ray crystallography. An alternate switching mechanism was observed by the intercalation of a bridging cyanide ligand between the two Mn–salphen moieties that resulted in the closing of the tweezers. These dual stimuli are attractive for achieving multiple controls of the mechanical motion of the tweezers. A crystallographic structure of unexpected partially oxidized closed tweezers was also obtained. One of the two Mn–salphen moieties underwent a ligand-centered oxidation of an imino to an amido group allowing an intramolecular Mn–Oamide–Mn linkage. The magnetic properties of the manganese(III) dimers were investigated to evaluate the magnetic exchange interaction and analyze the single molecule magnet behavior. [ABSTRACT FROM AUTHOR]

A family of mononuclear penta-coordinated CoII complexes, [Co(L)Cl2]·CH3OH (1), [Co(L)Br2] (2) and [Co(L)(NCS)2] (3) (where L is 1-mesityl-N,N-bis(pyridin-2-ylmethyl)methanamine) were synthesized and characterized. In these complexes, the neutral non-planar ligand, L, binds to three coordination sites around the metal center while two others are bound by anionic halide/pseudo halide ligands. The coordination geometry of the complexes is dictated by the coordinated anionic ligands. Thus, the coordination geometry around the metal ion is distorted trigonal bipyramidal for complexes 1 and 3, while it is distorted square pyramidal for complex 2. Ab initio CASSCF/NEVPT2 calculations on the complexes reveal the presence of an easy plane magnetic anisotropy with the D and E/D values being, 13.3 and 0.14 cm−1 for 1; 36.1 and 0.24 cm−1 for 2 and ±8.6 and 0.32 cm−1 for 3. These values are in good agreement with the values that were extracted from the experimental DC data. AC magnetic measurements reveal the presence of a field-induced slow relaxation of magnetization. However, clear maxima in the out-of-phase susceptibility curves were not observed for 1 and 3. For complex 2, peak maxima were observed when the measurements were carried out under an applied field of 1400 Oe which allowed an analysis of the dynamics of the slow relaxation of magnetization. This revealed that the relaxation is mainly controlled by the Raman and direct processes with the values of the parameters found to be: B = 0.77(15) s−1 K−6.35, n = 6.35(12) and A = 3.41(4) × 10−10 s−1 Oe−4 K−1 and m = 4 (fixed). The ab initio calculation which showed the multifunctional nature of the electronic states of the complexes justifies the absence of zero-field SIM behaviour of the complexes. The magnitude and sign of the D and E values and their relationship with the covalency of the metal–ligand bonds was analysed by the CASSCF/NEVPT2 as well as AILFT calculations. [ABSTRACT FROM AUTHOR]

We report the first bromine-bridged dinuclear [Dy(Cy3PO)2(μ-Br)(Br)2]2·2C7H8 single-molecule magnet with an effective energy barrier of 684 K and magnetic hysteresis below 3 K. The asymmetric DyIII centres present two unique stereoisomeric octahedral coordination environments depending on the cis/trans disposition of the Cy3PO ligands, leading to the orthogonality of the easy magnetic axes that annihilates the dipolar interactions. [ABSTRACT FROM AUTHOR]

The complexes [Ln2(hfac)6(L)]•nC6H14 (Ln = Dy (1) n = 0, Yb (2) n = 1) with the L chiral 3,14-di-(2-pyridyl)-4,13-diaza[6]helicene ligand (hfac- = 1,1,1,5,5,5-hexafluoroacetylacetonate) have been synthesized in their racemic form and structurally and magnetically characterized. Both complexes behave as field-induced single molecule magnets in the crystalline phase. These magnetic properties were rationalized by ab initio calculations. [ABSTRACT FROM AUTHOR]

A new family of three DyIII mononuclear complexes and one DyIII chain system based on the same ligand [1,3‐di(pyridin‐4‐yl)propane‐1,3‐dione] has been isolated as single crystals. By varying the synthesis conditions, it has been possible to finely control the number of ligands coordinated to the central lanthanide atom (from 1 to 3) and then the total charge of the complex unit (from +2 to neutral), as well as the local geometry around the DyIII ion (from D4d to D2d). The magnetic properties of the four complexes have been studied and rationalized by ab initio calculations to illustrate the correlation between the metal‐ion environment, due to the number of coordinated ligands, and their SMM behaviours. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The reaction between the 2,2'-benzene-1,4-diylbis(6-hydroxy-4,7-di-tert-butyl-1,3-benzodithiol-2-ylium-5-olate triad (H2SQ) and the metallo-precursor [Yb(hfac)3]⋅2H2O led to the formation of a dinuclear coordination complex of formula [Yb2(hfac)6(H2SQ)]⋅0.5CH2Cl2 (H2SQ-Yb). After chemical oxidation of H2SQ in 2,2'-cyclohexa-2,5-diene-1,4-diylidenebis(4,7-di-tert-butyl-1,3-benzodithiole-5,6-dione (Q), the latter triad reacted with the [Yb(hfac)3]⋅2H2O precursor to give the dinuclear complex of formula [Yb2(hfac)6(Q)] (Q-Yb). Both dinuclear compounds have been characterized by X-ray diffraction, DFT optimized structure and electronic absorption spectra. They behaved as field-induced Single-Molecule Magnets (SMMs) nevertheless the chemical oxidation of the semiquinone to quinone moieties accelerated by a factor of five the relaxation time of the magnetization of Q-Yb compared to the one for H2SQ-Yb. The H2SQ triad efficiently sensitized the YbIII luminescence while the chemical oxidation of H2SQ into Q induced strong modification of the absorption properties and thus a quenching of the YbIII luminescence for Q-Yb. In other words, both magnetic modulation and luminescence quenching are reached by the oxidation of the protonated semiquinone into quinone. [ABSTRACT FROM AUTHOR]

Abstract: The new thiocyanato- (5) and azido- (6) complexes were synthesized and studied under their Fe(II) and Fe(III) redox states. For the first time among the various [Fe(η5-C5Me5)(η2-dppe)]-based cationic radicals studied so far, the magnitude and spatial orientation of the g-tensor diagonal values were experimentally determined for 5[PF6]. These data are in good agreement with those issued from a DFT modelization. The changes experienced by the electronic structure of the Fe(II) complexes subsequent to oxidation are reminiscent of these previously observed for the known arylalkynyl analogues, albeit some differences can be pointed out. Thus, the differences observed in the 1H NMR spectra of 5[PF6] and 6[PF6] are attributed to a slower electronic spin relaxation and to the differently oriented magnetic anisotropy. The sizeable spin density evidenced by DFT on the terminal atom of the ligands of the Fe(III) complexes renders these new paramagnetic metallo-ligands quite appealing for accessing larger polynuclear molecular assemblies with magnetically interacting centers. [Copyright &y& Elsevier]

The Dy2 dinuclear complex behaves as a multi-field-induced Single-Molecule Magnet in which the two Ising Dy(III) ions display distinct relaxation times of their magnetization due to different magnetic relaxation processes. The reaction between the 2-(1-(4′-[4-(methylphenyl]-2,2:6′,2″-terpyridyl)-4,5-(4,5-bis(propylthio)-tetrathiafulvalenyl)-1H-benzimidazol-2-yl)-pyridine (L) and 2 equivalents of Dy(hfac) 3 ·2H 2 O (hfac− = 1,1,1,5,5,5-hexafluoroacetyacetonate) metallic precursors leads to the formation of a dinuclear complex of formula [Dy 2 (hfac) 6 (L)]·C 6 H 14 (Dy2). The X-ray structure on single crystal reveals the occupation of the two benzoimidazolylpyridine (bzip) and terpyridyl (terpy) coordination sites with a Dy(III) ion. The two D 4d and C 4v Dy(III) ions highlighted slow magnetic relaxation under an applied magnetic field. Even if the two lanthanide centers have similar magnetic anisotropy, they displayed different relaxation times of their magnetization which could be explained by the distinct nature of the magnetic relaxation processes. These conclusions are supported by ab initio calculations. [ABSTRACT FROM AUTHOR]

The [Dy(tta)3(L)] complex behaves as a single ion magnet both in its crystalline phase and in solution. Experimental and theoretical magnetic anisotropy axes perfectly match and lie along the most electro-negative atoms of the coordination sphere. Both VSM and MCD measurements highlight the robustness of the complex, with persistence of the memory effect even in solution up to 4 K. [ABSTRACT FROM AUTHOR]