Intrinsic Magnetic Properties Research Articles

First-Principles Study of Ti-Doping Effects on Hard Magnetic Properties of RFe11Ti Magnets

Due to the rare earth supply shortage, ThMn12-type RFe12-based (R is the rare earth element) magnets with lean rare earth content are gaining more concern. Most ThMn12-type RFe12 structures are thermodynamically metastable and require doping of the stabilizing element Ti. However, the Ti-doping effects on the hard magnetic properties of RFe11Ti have not been thoroughly investigated. Herein, based on density functional theory calculations, we report the Ti-doping effects on the phase stability, intrinsic hard magnetic properties and electronic structures of RFe11Ti (R = La, Ce, Pr, Nd, Sm, Y, Zr). Our results indicate that Ti-doping not only increases their phase stability, but also enhances the magnetic hardness of ground-state RFe12 phases. Particularly, it leads to the transition of CeFe11Ti and PrFe11Ti from easy-plane to easy-axis anisotropy. Charge density distributions demonstrate that Ti-doping breaks the original symmetry of the R-site crystal field, which alters the magnetic anisotropy of RFe11Ti. Projected densities of states reveal that the addition of Ti results in the shift of occupied and unoccupied f-electron energy levels of rare earth elements, affecting their magnetic exchange. This study provides an insight into regulating the hard magnetic properties of RFe12-based magnets by Ti-doping.

High Cerium content Fe‐Ce‐Nd‐B sintered magnets with high coercivity

Ce substitution of Nd in FeNdB sintered magnets is very interesting for reasons of resource efficiency, sustainability and costs. However, the magnetic properties of high Ce‐content magnets are poor. This is mainly due to the lower values of intrinsic magnetic properties of Fe14Ce2B compared to Fe14Nd2B as well as the Laves phase Fe2Ce, which is formed in the grain boundaries and forms flat aggregates for higher Ce‐content. In this paper, sintered magnets with 75 at% degree of substitution of the composition Fe70.9‐[(Ce1‐xLax)0.75Nd0.25]18.8‐B5.8‐M4.5 (M = Co, Ti, Al, Ga, Cu, 0 ≤ × ≤ 0.3) are produced and analyzed. It is shown that a new rare earth rich grain boundary phase is formed adding La and that the Laves phase fraction can be reduced by up to 85%. With increasing La content, the remanence and Curie temperature increase and the temperature coefficient of Hc improves. A coercivity, remanence and maximum energy density of up to µ0Hc = 0.74 T, Jr = 0.98 T and (BH)max = 139.9 kJ/m3 have been achieved.This article is protected by copyright. All rights reserved.

Excellent intrinsic magnetic properties in the TbCu7-type Sm-Fe-N compound

We report excellent intrinsic magnetic properties of SmFe9Nδ (δ=0, 0.5, 0.7 and 1.1) epitaxial thin films with TbCu7-type crystal structure, i.e., room temperature saturation magnetization (μ0Ms) of 1.64 T, Curie temperature (Tc) of 771 K and magnetic anisotropy field (μ0HA) of ∼22 T for δ=1.1 the saturation magnetization of which is superior to that of Sm2Fe17N3 (μ0Ms= 1.57 T) and Nd2Fe14B compounds (μ0Ms= 1.61 T). X-ray diffraction and transmission electron microscopy revealed that the thin films have a highly textured single TbCu7-type phase with its c-axis perpendicular to the film. Heat treatment of the thin films under N atmosphere expands the lattice and increases the unit cell volume of the SmFe9Nδ structure, which also switches the magnetocrystalline anisotropy from easy plane (δ = 0) to easy axis (δ=1.1). Furthermore, the μ0Ms and Tc of SmFe9Nδ films also increased with increasing nitrogen content in the structure, leading to promising intrinsic magnetic properties. Based on this study, we can conclude that the rare-earth lean SmFe9Nδ based TbCu7-type compound has potential for the development of high performance anisotropic bonded magnets with superior performance to that of existing anisotropic Sm2Fe17N3 or Nd-Fe-B bonded magnets.

Confining single Er3+ ions in sub-3 nm NaYF4 nanoparticles to induce slow relaxation of the magnetisation

Molecular systems known as single-molecule magnets (SMMs) exhibit magnet-like behaviour of slow relaxation of the magnetisation and magnetic hysteresis and have potential application in high-density memory storage or quantum computing. Often, their intrinsic magnetic properties are plagued by low-energy molecular vibrations that lead to phonon-induced relaxation processes, however, there is no straightforward synthetic approach for molecular systems that would lead to a small amount of low-energy vibrations and low phonon density of states at the spin-resonance energies. In this work, we apply knowledge accumulated over the last decade in molecular magnetism to nanoparticles, incorporating Er3+ ions in an ultrasmall sub-3 nm diamagnetic NaYF4 nanoparticle (NP) and probing the slow relaxation dynamics intrinsic to the Er3+ ion. Furthermore, by increasing the doping concentration, we also investigate the role of intraparticle interactions within the NP. The knowledge gained from this study is anticipated to enable better design of magnetically high-performance molecular and bulk magnets for a wide variety of applications, such as molecular electronics.

The effects of V doping on the intrinsic properties of SmFe10Co2 alloys: A theoretical investigation

The present study focuses on the intrinsic properties of the SmFe10Co2-xVx (x = 0–2) alloys, which includes the SmFe10Co2 alloy, one of the most promising permanent magnets with the ThMn12 type of structure due to its large saturation magnetization (µ0Ms = 1.78 T), high Curie temperature (Tc = 859 K), and anisotropy field (µ0Ha = 12 T) experimentally obtained. Unfortunately, its low coercivity (<0.4 T) hinders its use in permanent magnet applications. The effect of V-doping on magnetization, magnetocrystalline anisotropy energy, and Curie temperature is investigated by electronic band structure calculations. The spin-polarized fully relativistic Korringa-Kohn-Rostoker (SPR-KKR) band structure method, which employs the coherent potential approximation (CPA) to deal with substitutional disorder, has been used. The Hubbard-U correction to local spin density approximation (LSDA + U) was used to account for the large correlation effects due to the 4f electronic states of Sm. The computed magnetic moments and magnetocrystalline anisotropy energies were compared with existing experimental data to validate the theoretical approach’s reliability. The exchange-coupling parameters from the Heisenberg model were used for obtaining the mean-field estimated Curie temperature. The magnetic anisotropy energy was separated into contributions from transition metals and Sm, and its relationships with the local environment, interatomic distances, and valence electron delocalization were analyzed. The suitability of the hypothetical SmFe10CoV alloy for permanent magnet manufacture was assessed using the calculated anisotropy field, magnetic hardness, and intrinsic magnetic properties.

Development of polymeric nanoparticles associated with SPION and curcumin: a versatile magnetic and fluorescent platform for Life Science applications

Magnetic nanoparticles are prominent in biomedical applications due to their adjustable properties through surface functionalization and inherent magnetism. In the present manuscript, multifunctional nanoparticles were synthesized by combining polymer with a fluorophore and magnetic nanoparticles, resulting in a magnetic and fluorescent nanomaterial. A miniemulsion polymerization technique was employed, using the comonomers methyl methacrylate (MMA) and acrylic acid (AA) in the presence of superparamagnetic iron oxide nanoparticles (SPIONs) and natural turmeric extract (curcumin). Physicochemical characterizations revealed efficient encapsulation of SPIONs within the polymer matrices while maintaining superparamagnetic behavior. The nanosystems exhibited ILP values consistent with those commonly used for magnetic hyperthermia applications, ranging from 0.13 – 0.32 nHm2 kg−1. Additionally, a high fluorescence intensity in the blue/green region was observed, alongside no cell toxicity and substantial internalization in human osteosarcoma cells (OSAS2). Given their intrinsic magnetic and fluorescent properties exhibited, the nanosystems can be considered potential candidates for cell tracking and as a platform in nanotheranostics (MRI, magnetic hyperthermia, and photodynamic therapy).

Revisiting the Young’s model for ferrofluid droplets: Magnetowetting or magneto-dewetting?

Magnetic field-mediated wetting of ferrofluid droplets has emerged to be of fundamental importance because of its plethora of applications ranging from chemical and biomolecular analysis to soft robotics and medical imaging. However, while extensive studies continue to be reported on the underlying experimental facets, a fundamental theoretical depiction of the observed contact angle variation with the applied magnetic field remains grossly elusive, as attributable to a complex dependence of the induced magnetization on the droplet’s intrinsic magnetic properties. Circumventing these constraints, here we put forward a first-principle analytical model that delineates the variation in the contact angle as a function of an applied magnetic field on a sessile ferrofluid droplet, by appealing to energy minimization principles. One key feature of our analysis is the consideration of the local magnetization as a function of the magnetic field itself, resulting in a new contribution to the interfacial energy by virtue of normal traction at the droplet's contact with its non-magnetic surroundings. This theory is supported by experiments identified in prior research to elucidate the fundamental physics of relevance. Our results highlight the substantial influence of the saturation magnetization and the initial susceptibility of the ferrofluid on the resulting contact angle alterations, as well as possible non-trivial routes of highly selective and precise enhancement or attenuation in the extent of wetting. These findings are likely to be of fundamental importance towards establishing the design foundations of portable magnetic resonance imaging devices, micromixers, and microreactors, magnetically-manipulated automatic control of soft fluidic matters, among others.

Magnetic Nanoparticles with Aspects of their Use in Cancer Therapy

Abstract: Cancers remain the leading cause of death worldwide, despite significant advances in their diagnosis and treatment. The inadequacy and ineffectiveness of standard treatments (chemotherapy, radiotherapy, and surgery), their severe side effects, and the resistance of tumor cells to chemotherapeutics have forced researchers to investigate alternative therapeutic strategies. Magnetic nanoparticles (MNPs) have been evaluated as one of the promising strategies in treating cancers, a major public health problem. Due to their intrinsic magnetic properties, MNPs are tools that can be designed to be multifunctional in medicine, including cancer therapy. Multifunctionality can be achieved with various drug/agent loadings, such as chemotherapeutic drugs, radionuclides, nucleic acids, and antibodies. This provides a multimodal theranostics platform for cancer diagnosis, monitoring, and therapy. These substances can then be delivered to the tumor tissue using an external magnetic field (EMF). Magnetic or photothermal applications kill cancer cells at the tumor site by inducing local hyperthermia, whereas photodynamic therapy kills them by producing reactive oxygen species. MNP applications also prevent drug resistance. In addition, alone or with different combination options, MNP applications provide synergistic effects and reduce side effects. Functionalized MNPs can be used to remove unwanted cells from blood, including circulating tumor cells (CTCs), which are key factors in the metastatic process and leukemia cells. Despite numerous successful studies, there are some unpredictable obstacles to be discovered in routine usage. This review focuses mainly on the application of MNPs in cancer treatment, covering future perspectives and challenges.

Robustness of magnetocrystalline anisotropy and coercivity in Fe–Co–B

As a potential candidate for critical chemical element free permanent magnet, (Fe0.7Co0.3)2B, shows promising intrinsic magnetic properties, including large magnetization, high Curie temperature and moderate magnetocrystalline anisotropy (MCA). Still, the coercivity that has been achieved is relatively low. To understand and improve coercivity, we study the robustness of MCA related to the fluctuation of chemical composition and the structural distortion and its effect on coercivity in (Fe0.7Co0.3)2B from first principles DFT (density functional theory) calculation and micromagnetic simulation. A fluctuation of cobalt content of 10%, or 1% isotropic lattice strain, or 2% tetragonal distortion reduces MCA energy up to 30%. By considering randomly distributed local MCA energy reduction up to 30%, the calculated coercivity of anisotropic bulk magnets reduced from 3.6 kOe to 2.2 kOe. Rational microstructure design, such as grain size refinement and development of strong crystal texture of MCA easy-axis (i.e., degree of alignment for (Fe0.7Co0.3)2B grains), can enhance coercivity and mitigate the effect of local MCA reduction. In addition to acceptable intrinsic magnetic properties, the promising hard magnetic phase needs good MCA robustness to facilitate the development of practical magnets.

Intrinsic magnetism of an individual rare-earth atom on transition metal dichalcogenide semiconductors

Two-dimensional (2D) structures that exhibit intriguing magnetic phenomena such as perpendicular magnetocrystalline anisotropy (PMA) have become a focus of spintronic research due to their potentials in maximizing the information storage density. Herein we perform density-functional theory plus U (DFT+U) calculations to investigate the binding affinity and intrinsic magnetic properties of an individual rare-earth (RE) Sm atom on WSe2 monolayer. Our calculations show that Sm adatom energetically prefers to adsorb at the W-top site in WSe2 rather than the Se-top and hollow sites. We predict extremely large PMA values of ∼7–33 meV per Sm at the most stable W-top site, depending on U parameter in DFT+U calculations, while it is negligibly small for the Se-top and hollow sites. The underlying mechanism for large PMA is elucidated in terms of the strong spin–orbit coupled Sm 4f – W 5d orbital states and large 4f orbital magnetic moment in the high-spin crystal field. These results provide a viable route to achieving an atomic scale f-electron PMA in 2D structures, opening interesting prospects in two-dimensional semiconducting spintronics.

Magnetic Hydroxyapatite Nanoparticles in Regenerative Medicine and Nanomedicine.

This review focuses on the latest advancements in magnetic hydroxyapatite (mHA) nanoparticles and their potential applications in nanomedicine and regenerative medicine. mHA nanoparticles have gained significant interest over the last few years for their great potential, offering advanced multi-therapeutic strategies because of their biocompatibility, bioactivity, and unique physicochemical features, enabling on-demand activation and control. The most relevant synthetic methods to obtain magnetic apatite-based materials, either in the form of iron-doped HA nanoparticles showing intrinsic magnetic properties or composite/hybrid compounds between HA and superparamagnetic metal oxide nanoparticles, are described as highlighting structure-property correlations. Following this, this review discusses the application of various magnetic hydroxyapatite nanomaterials in bone regeneration and nanomedicine. Finally, novel perspectives are investigated with respect to the ability of mHA nanoparticles to improve nanocarriers with homogeneous structures to promote multifunctional biological applications, such as cell stimulation and instruction, antimicrobial activity, and drug release with on-demand triggering.

Phase evolution, microstructure, and improved magnetic properties for off-stoichiometric SmFe12-based alloys

Low rare earth content and high intrinsic magnetic properties make SmFe12-based permanent magnets a potential candidate for NdFeB-based magnets in medium to high temperature environments. However, the easy formation of multiple ferromagnetic intergranular phases limits the preparation of high coercivity magnets. Composition optimization is an indispensable measure for the realization of high-performance magnets. In this work, off-stoichiometric composition design is employed to prepare SmFe12-based alloys. Ti is first introduced to inhibit the precipitation of α-Fe phase, obtaining a high coercivity of 484 kA/m, while the ribbon undergoes a reduction of remanence significantly. After regulating Fe–Co content to 11.5, the remanence recoveries from 0.51 to 0.65 T with a slight increase in coercivity (484–493 kA/m). Finally, Fe content is optimized to further improve magnetic properties, with both coercivity and remanence are improved simultaneously, reaching 509 kA/m and 0.70 T, respectively. Phase evolution, microstructure and their relationship with magnetic properties are investigated in detail. Micromagnetic simulation shows that the increased domain wall pinning effect induced by the refinement of grain size is the main reason for high coercivity. This work provides a feasible compositional design method for the preparation of high performance SmFe12-based alloys.

Fe-Ni based alloys as rare-earth free gap permanent magnets

L10-ordered FeNi phase has potential as a rare-earth free permanent magnet due to its large magnetization and high Curie temperature. However, low long-range crystal ordering and weak magnetocrystalline anisotropy (Ku) impede its practical use in a technologically relevant permanent magnet. Employing density functional and Monte Carlo simulations, we demonstrate the substantial improvements on structural and thermal stability, disorder-order phase transition, and intrinsic permanent magnetic properties of Fe−Ni structures. We propose that this is achievable through the complementary elemental substitutions by metal elements (M) and interstitial doping with 2p elements. Fe1-xMxNi with simple metal (M = Ga and Al) and metalloid (M = Ge and Si) elemental substitutions at x = 0.5 are broadly known as Heusler (L21) structures with no permanent magnet characteristics. On the contrary, we find that for x = 0−0.5, L10-type structure is energetically favored over the Heusler-type structures. The predicted structures exhibit Ku values up to approximately 2.1 MJ/m3, which is roughly three times that of FeNi phase (0.68 MJ/m3), where the absolute value of Ku depends on the degree of L10 crystal ordering. Interstitial doping with B elevates Ku further up to a maximum value of 3.9 MJ/m3 (at 0 K), leading to room-temperature intrinsic permanent magnetic properties, including maximum energy density product (BH)max, anisotropy field μ0Ha, and hardness parameter κ, comparable to the widely investigated MnBi and MnAl permanent magnets. These results may serve as a guideline in designing Fe−Ni based rare-earth free gap permanent magnetic materials that were previously overlooked.

Zr substituted (Nd, Zr)(Fe, Co, Mo)12N compounds with high intrinsic magnetic properties

The Fe-rich ThMn12-type compounds show great promise as permanent magnetic materials. In this work, the structure and magnetic properties of (Nd, Zr)(Fe, Co, Mo)12N compounds have been systematically studied. The spherical aberration corrected scanning transmission electron microscopy images and neutron diffraction results confirm that Zr and Mo occupy the 2a and 8i sites, respectively. It is found suitable Co substitution can further enhance the μ0Ha and Tc of Nd0.7Zr0.3Fe11.2Mo0.8N. Nd0.7Zr0.3(Fe0.75Co0.25)11.5Mo0.5N has the excellent intrinsic magnetic properties of Ms = 164.9 Am2/kg, Tc = 964.4 K, and μ0Ha = 9.12 T, of which Ms is close to Nd2Fe14B, but Tc and μ0Ha are much higher. In addition, (Nd, Zr)(Fe, Mo)12N have higher purity and larger μ0Ha than (Nd, Zr)(Fe, Ti)12N, which shows great potential for practical applications.

Hayabusa 2 returned samples reveal a weak to null magnetic field during aqueous alteration of Ryugu's parent body

The JAXA Hayabusa 2 mission returned 5.4 g of material from the C-type asteroid Ryugu. The Mn-Cr ages of dolomite in the returned samples indicate that Ryugu's parent body experienced aqueous alteration sometimes between <1.8 and 6.8 Myr after CAI formation. Because this time range overlaps with the lifetime of the solar nebula, we investigate the possibility that magnetite and pyrrhotite, which are aqueous alteration products found in Ryugu samples, acquired a remanent magnetization reflecting the nebula field intensity. We analyze the intrinsic magnetic properties and paleomagnetic record of three Ryugu samples of 0.82, 0.97 and 21.87 mg. None of the samples exhibit a stable natural remanent magnetization. This indicates that the aqueous alteration of Ryugu's parent body took place either in a field of a few µT, or in a very weak to null field. In the former scenario, the solar nebula field is the most likely magnetizing field, implying that aqueous alteration occurred before its dissipation, i.e., before ∼5 Myr after CAI formation. In the latter scenario, aqueous alteration must have occurred either after the dissipation of the nebula, or at an earlier epoch and a large heliocentric distance (> 5 au). The similarities between Ryugu samples and CI chondrites favor this second hypothesis. Our results contrast with another paleomagnetic study of two Ryugu samples, arguing for a paleofield intensity of 40 to 390 µT. Our interpretation of this discrepancy is that these samples were exposed to artificial magnetic fields (> mT) during preceding experiments. This highlights the importance of conducting, as much as possible, the paleomagnetic investigations of returned samples before any other experiment. We also demonstrate that the ratio of NRM over low-field magnetic susceptibility is a powerful, non-destructive indicator of magnetic contamination. We recommend measuring this ratio routinely before paleomagnetic investigations of meteorites and returned samples.

Microstructure and coercivity of Al-diffused Sm(Fe,Co,B)12 film

Fe-rich SmFe12-based compounds are considered as potential next generation permanent magnets due to their excellent intrinsic magnetic properties. However, their reported coercivities remain low, only ∼12 % of the magnetic anisotropy field of the SmFe12-based compound. In this work, we successfully increased the coercivity of B-doped Sm(Fe0.8Co0.2)12-based thin films from 1.1 T to 1.8 T by diffusion of Al into the grain boundaries. Detailed microstructural characterization using scanning transmission electron microscopy (STEM) and atom probe tomography (APT) revealed that the high coercivity is due to the segregation of Al into ∼4 nm thin B-rich amorphous intergranular phase, resulting in a reduction of its magnetization. This compositional modification of the intergranular phase can prevent the nucleation of reversed magnetic domains in the triple junctions and increase the pinning force of the grain boundary region against the magnetic domain wall motion. Based on detailed microstructural observations, the mechanism of coercivity enhancement is discussed.

Magnetic Anisotropy Tailoring by 5d-Doping in (Fe,Co)5SiB2 Alloys

Band-structure calculations were performed using the spin-polarized relativistic Korringa–Kohn–Rostoker (SPR-KKR) band-structure method, determining intrinsic magnetic properties, such as magnetic moments, magnetocrystalline anisotropy energy (MAE), and Curie temperatures, of Fe5−x−yCoxMySiB2 (M = Re, W) alloys. The general gradient approximation (GGA) for the exchange–correlation potential and the atomic sphere approximation (ASA) were used in the calculations. Previous studies have shown that for Fe5SiB2, the easy magnetization direction is in-plane, but it turns axial for Co-doping in the range 1 &lt; x ≤ 2.5 (y = 0). Furthermore, studies have shown that 5d-doping enhances the MAE by enabling the strong spin–orbit coupling of Fe–3d and M–5d states. The aim of the present theoretical calculations was to find the dependence of the anisotropy constant K1 for combined Co- and M-doping, building a two-dimensional (2D) map of K1 for 0 ≤ x ≤ 2 and 0 ≤ y ≤ 1. Similar theoretical 2D maps for magnetization and Curie temperature vs. Co and M content (M = W and Re) were built, allowing for the selection of alloy compositions with enhanced values of uniaxial anisotropy, magnetization, and Curie temperature. The magnetic properties of the Fe4.1W0.9SiB2 alloy that meet the selection criteria for axial anisotropy K1 &gt; 0.2 meV/f.u., Curie temperature Tc &gt; 800 K determined by the mean-field approach, and magnetization µ0Ms &gt; 1 T are discussed.

Nanocrystalline alternative rare earth-iron-boron permanent magnets without Nd, Pr, Tb and Dy: A review

The continuous increase in the output of Nd-Fe-B permanent magnets leads to the increasing consumption of rare earth (RE) metals of Nd, Pr, Tb and Dy. As a result, a serious unbalanced utilization of RE resource occurs. To reduce the use of these critical REs, high abundance REs of Y, La, Ce and even Gd and Ho have been proposed to partly substitute Pr and Nd in sintered magnets and rapid-quenched nanocrystalline magnetic powders. Recently, the cost-effective RE-Fe-B magnets without Nd, Pr, Tb and Dy have also been developed. This type of magnet is preliminarily designed to bridge the magnetic properties gap between hard ferrites and bonded Nd-Fe-B magnets, which shows the potential applications in voice coil motor, spindle motors and magnetic resonance imaging systems. This review summarizes the progress of RE-Fe-B-type magnets containing no Nd, Pr, Dy and Tb based on the world-wide investigations and our recent findings. The fundamentals of intrinsic magnetic properties of Y, La, Ce based RE2Fe14B phases are introduced first. The relationship between magnetic properties and microstructure of rapidly quenched and bulk RE-Fe-B magnets with nanocrystalline structure is then emphatically discussed. Hard magnetic properties and performance/cost ratio of various RE-Fe-B alloy systems are summarized and compared. Furthermore, the current discoveries and the existing challenges are discussed. Some potential strategies for the future research in this field are finally proposed.

Magnetic properties enhancement of multi-element-doped SmCo7 nanocrystalline alloys

TbCu7-type SmCo7-based permanent magnets possess great potential for applications in high-temperature service because of their large magnetocrystalline anisotropy and low temperature coefficient of coercivity. However, the application of SmCo7-based alloys is seriously limited by the trade-off between the TbCu7-type phase stability and the intrinsic magnetic properties, as well as the balance between the saturation magnetization and the coercivity. In this study, a series of SmCo7-based nanocrystalline alloys doped by Mn, Cu, and Fe elements were prepared. The TbCu7-type phase was well stabilized by nanostructuring and appropriate doping. Tailoring the element doping enhanced the coercivity by 50 % and achieved a balance between the saturation magnetization and the coercivity of the SmCo7-based nanocrystalline alloys. The mechanisms of the magnetic properties enhancement were disclosed based on the characterization of microstructures and magnetic structures. It is proposed that a high proportion of the TbCu7-type SmCo7 main phase is critical to achieve excellent magnetic properties. This study provides both the method and rules for the development of multi-component Sm-Co-based alloys with high integrated magnetic properties.

Expanding the Coordination of f-Block Metals with Tris[2-(2-methoxyethoxy)ethyl]amine: From Molecular Complexes to Cage-like Structures.

Low-valent f-block metals have intrinsic luminescence, electrochemical, and magnetic properties that are modulated with ligands, causing the coordination chemistry of these metals to be imperative to generating critical insights needed to impact modern applications. To this end, we synthesized and characterized a series of twenty-seven complexes of f-metal ions including EuII, YbII, SmII, and UIII and hexanuclear clusters of LaIII and CeIII to study the impact of tris[2-(2-methoxyethoxy)ethyl]amine, a flexible acyclic analogue of the extensively studied 2.2.2-cryptand, on the coordination chemistry and photophysical properties of low-valent f-block metals. We demonstrate that the flexibility of the ligand enables luminescence tunability over a greater range than analogous cryptates of EuII in solution. Furthermore, the ligand also displays a variety of binding modes to f-block metals in the solid state that are inaccessible to cryptates of low-valent f-block metals. In addition to serving as a ligand for f-block metals of various sizes and oxidation states, tris[2-(2-methoxyethoxy)ethyl]amine also deprotonates water molecules coordinated to trivalent triflate salts of f-block metal ions, enabling the isolation of hexanuclear clusters containing either LaIII or CeIII. The ligand was also found to bind more tightly to YbII and UIII in the solid state compared to 2.2.2-cryptand, suggesting that it can play a role in the isolation of other low-valent f-block metals such CfII, NpIII, and PuIII. We expect that our findings will inspire applications of tris[2-(2-methoxyethoxy)ethyl]amine in the design of light-emitting diodes and the synthesis of extremely reducing divalent f-block metal complexes that are of interest for a wide range of applications.