Unexpected appearance of molecular ferromagnetism in the ordinary acetate [[Gd(OAc)3(H2O)2]2].4 H2O

Gd(OH)F2: A Promising Cryogenic Magnetic Refrigerant

Magnetic refrigerants with a large magnetocaloric effect (MCE) in a wide temperature range and low magnetic ordering temperature (T_o) in the sub-kelvin temperature region are not only crucial for adiabatic demagnetization refrigeration but also open up a broader parameter space for the optimal design of adiabatic demagnetization refrigerators. However, such magnetic refrigerants are extremely rare because they require magnetic materials to simultaneously satisfy three conditions: low T_o, weak magnetic interaction, and high magnetic density. Here, we report the syntheses, heat capacities, and magnetic properties of Gd(OH)_3-xF_x (1: x = 1, 2: x ≈ 1.5, and 3: x = 2), demonstrating for the first time that the introduction of fluoride anions into antiferromagnetic Gd(OH)₃ can effectively regulate its T_o. Significantly, 3 not only has a T_o of 0.5 K but also exhibits a large MCE in the temperature range from 0.5 to 4 K, representing the best magnetic refrigerant reported to date in the temperature range of 0.5-4 K from the viewpoint of the MCE.

A magnetocaloric glass from an ionic-liquid gadolinium complex

[Gd 5 (L) 16 (H 2 O) 8 ](Tf 2 N) 15 was obtained from reaction of Gd 2 O 3 with 1-carboxymethyl-3-ethylimidazolium chloride (LHCl). The material was found to be an ionic liquid that freezes to glassy state on cooling to -30°C. Variable-temperature magnetic studies reveal the presence of weak magnetic intramolecular interactions in the glass. Isothermal variable-field magnetization demonstrates a magnetocaloric effect (MCE), which is the first finding of such an effect in a molecular glass. This MCE explainable by an uncoupled representation, with a magnetic entropy change of -11.36 J K -1 kg -1 at 1.8 K for a 0-7 T magnetic field change, and with a refrigerant capacity of 125.9 J kg -1 , in the 1.8-50 K interval.

Multifunctionality of the [C2mim][Ln(fod)4] series (Ln = Nd–Tm except Pm): magnetic, luminescence and thermochemical studies

The [C2mim][Ln(fod)4] series presents a rare and reversible polymorphism, NIR and visible emission as well as SMM behavior. The varieties of physical behaviors make these compounds suitable for potential technological and/or biomedical applications.

The coordination chemistry of benzhydrazide with lanthanide(iii) ions: hydrothermal in situ ligand formation, structures, magnetic and photoluminescence sensing properties

The influence of synthetic conditions on the solid-state structural formation of lanthanide(iii) complexes based on a hydrazide ligand have been investigated and reported. Depending on the solvents and reaction temperatures, the reactions of hydrated Ln(NO₃)₃ with a benzohydrazide (bzz) ligand afforded three classes of lanthanide(iii) coordination complexes viz. [Ln(bzz)(NO₃)](NO₃)₂ (1Ln; Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5)), [Ln(bzz)(ben)₃(H₂O)]·H₂O (2Ln; Ln = Pr (6), Nd (7), Sm (8), Eu (9), Gd (10), Tb (11), Dy (12), Er (13)), and [Ln₃(ben)₃] (3Ln; Ln = Eu (14), Gd (15), Tb (16), Dy (17), Er (18), Tm (19), Yb (20), Lu (21)). Complexes 1-5 in series 1Ln were isolated by slow evaporation of their isopropanol solutions at ambient temperature, and the complexes display similar discrete structures bearing distinct intermolecular N-H⋯O hydrogen bonds to generate a three-dimensional (3D) supramolecular architecture. Complexes 6-13 in series 2Ln were obtained under hydrothermal conditions at 110 °C where the in situ generated benzoate (ben) ligands participated in the formation of one-dimensional (1D) coordination polymers (CPs) with the bzz ligands. At a temperature of 145 °C the hydrothermal conditions result in the formation of the thermodynamically more stable products of 14-21 in series 3Ln, in which the bzz ligand underwent complete in situ hydrolysis to create the ben ligand. These coordination assemblies feature 1D zigzag chains that are formed by unusual low coordination numbers of the six- and seven-fold coordinated Ln³⁺ centers bridged by the ben ligands in μ ₂- and μ ₃-coordination modes. Notably, the chain structures of 2Ln can be transformed into the zigzag tape-like structures of 3Ln upon heating the crystalline samples to 400 °C in air. In the solid state at room temperature, the Eu- (2, 9, 14) and Tb- (4, 11, 16) containing complexes emit red and green light, respectively. The luminescence investigations show that the Eu- (9, 14) and Tb-(11, 16) based CPs could be used as fluorescent probes for acetone and Co²⁺ ions via an energy competition mechanism. Meanwhile, the Gd- (10, 15) and Dy- (12, 17) based CPs show typical antiferromagnetic interactions.

Heterometallic 3d–4f {Co2Gd4} phosphonates: new members of the potential magnetic cooler family

Three new 3d–4f heterometallic phosphonate complexes with the formula [Na₂CoIII2Gd₄(L)₆(bpy)₂(OR)₂]·nSolv (L = SAA³⁻(1), BSAA³⁻(2), and NAA³⁻(3); bpy = 2,2′-bipyridine; OR = OH and OMe; Solv = H₂O and MeOH) were isolated and studied in detail.

Facile and environmentally friendly synthesis of six heterometallic dumbbell-shaped MLn (M = Co, Ni; Ln = Eu, Gd, Dy) clusters as cryogenic magnetic coolants and molecular magnets

Six analogous dumbbell-shaped 3d-4f complexes MLn were obtained by the reaction of Ln(NO₃)₃ (Ln = Eu, Gd, Dy) and M(OAc)₂ (M = Co, Ni) without any other organic ligands, and M₅Gd₄ exhibited a large magnetocaloric effect (-ΔS_m = 31.0, 37.3 J kg^-1 K^-1 for Co₅Gd₄ and Ni₅Gd₄ respectively), while M₅Dy₄ and Co₅Eu₄ showed single molecule magnet behaviour. To the best of our knowledge, Co₅Eu₄ is the first Eu-based cluster to display single molecule magnet behaviour (U_eff = 16.4 K).

Synthesis, structure and magnetic investigations of dinuclear lanthanide complexes based on 2-ethoxycinnamate

A series of dinuclear lanthanide complexes incorporating the 2-ethoxycinnamate ligand have been synthesized and characterized using elemental analyses, infra-red spectroscopy, X-ray diffraction and magnetic measurements. Depending on the nature of the lanthanide ion, three different isostructural series of respective formulas, [Ln(L)3(DMSO)(H2O)]2 (Ln = Ce (1), Nd (2)), [Ln(L)3(DMSO)x(DMF)y(H2O)]2 (Ln = Gd (3), Dy (5) and Er (6)) and [Tb(L)3(DMF)(H2O)]2 (4) have been obtained. Investigations of their magnetic properties reveal a genuine single-molecule magnet behaviour observed for the dysprosium based compound 5, while a field-induced slow relaxation of the magnetization is found for compounds 1, 2 and 3.

Giant Exchange Coupling Evidenced with a Magnetization Jump at 52 T for a Gadolinium-Nitroxide Chelate

The Gd-radical complex [Gd^III(hfac)₃(6bpyNO)] (6bpyNO = 2,2'-bipyridin-6-yl tert-butyl nitroxide; Hhfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione) showed a magnetization jump at 52 T observed in a pulsed-field facility, corresponding to an exchange coupling constant of -17.4 K. Furthermore, hysteretic behavior due to a relatively slow magnetization reversal was recorded around 2 T. From the high-frequency EPR study, the exchange coupling between Gd and radical spins accompanies an anisotropic character, which is responsible for both the broad jump and the slow magnetization reversal.

Cinnamic acid derivative rare-earth dinuclear complexes and one-dimensional architectures: synthesis, characterization and magnetic properties

Discrete and extended architectures based on two derivatives of cinnamic acid show slow relaxation of the magnetisation.

Understanding the magnetism of {Fe2Ln} dimers, step-by-step

A hierarchical, comparative approach to the complex magnetochemistry of {Fe₄M₂}-type coordination clusters (M = Y, Eu, Gd, Dy) allows determination of intramolecular exchange energies.

Multiple magnetic relaxation processes, magnetocaloric effect and fluorescence properties of rhombus-shaped tetranuclear rare earth complexes

A multi-relaxation single-molecule magnet (SMM) of a {Dy₄} complex exhibits two distinct relaxation processes, with a high energy barrier of 121 K.

Mononuclear and polynuclear complexes ligated by an iminodiacetic acid derivative: synthesis, structure, solution studies and magnetic properties

Two novel families of coordination polymers, [Ln(bzlida)(Hbzlida)]·H₂O (Ln = La, Nd) and [Ln₂(bzlida)₃]·3H₂O (Ln = Nd, Sm, Eu, Gd) were prepared by hydrothermal reaction of Ln₂O₃ with benzyliminodiacetic acid.

Building 1D lanthanide chains and non-symmetrical [Ln2] “triple-decker” clusters using salen-type ligands: magnetic cooling and relaxation phenomena

Three series of related lanthanide polymers/dimers have been structurally and magnetically investigated.

Three sra topological lanthanide–organic frameworks built from 2,2′-dimethoxy-4,4′-biphenyldicarboxylic acid

The first neutral 3D sra-LOF built from a 1D inorganic rod-shaped chain [Ln(CO₂)₂(HCO₂)]_n (Ln = Eu, Gd, Dy) was synthesized.

Diversity of lanthanide(III)-2,5-dihydroxy-1,4-benzenedicarboxylate extended frameworks: syntheses, structures, and magnetic properties

Six lanthanide(III)-2,5-dihydroxy-1,4-benzenedicarboxylate frameworks, namely, [Ln(H(2)-DHBDC)(1.5)(H(2)O)(2)](n) (Ln = La (1) and Pr (2); H(4)-DHBDC = 2,5-dihydroxy-1,4-benzenedicarboxylic acid), {[Nd(H(2)-DHBDC)(1.5)(H(2)O)(3)](H(2)O)}(n) (3), {[Eu(H(2)-DHBDC)(NO(3))(H(2)O)(4)](H(2)O)(2)}(n) (4), and {[Ln(2)(H(2)-DHBDC)(2)(DHBDC)(0.5)(H(2)O)(3)](H(2)O)(4)}(n) (Ln = Gd (5) and Dy (6)), with four different structural types ranging from 1D chain, 2D layer to 3D networks have been synthesized and structurally characterized. Compounds La (1) and Pr (2) are isomorphous and exhibit 3D frameworks with the unique 1D tubular channels. Compounds Nd (3) and Eu (4) are 2D layer and 1D zigzag chain, respectively, which are further extended to 3D supramolecular frameworks through extensive hydrogen bonds. Isomorphous compounds of Gd (5) and Dy (6) are 3D frameworks constructed from secondary infinite rod-shaped metal-carboxylate/hydroxyl building blocks. While the hydroxyl groups as secondary functional groups in the 1D chain of Eu (4) and 2D layer of Nd (3) are not bonded to the lanthanide centers, the hydroxyl groups in the 3D frameworks of La (1), Pr (2), Gd (5), and Dy (6) participate in coordinating to lanthanide centers and thus modify the structural types of theses compounds. The magnetic data of compounds Pr (2), Nd (3), Gd (5), and Dy (6) have been investigated in detail. In addition, elemental analysis, IR spectra, powder X-ray diffraction (PXRD) patterns and thermogravimetric analysis of these compounds are described.