Series of Isostructural Planar Lanthanide Complexes [LnIII4(μ3-OH)2(mdeaH)2(piv)8] with Single Molecule Magnet Behavior for the Dy4 Analogue

Designing Quantum Spaces of Higher Dimensionality from a Tetranuclear Erbium-Based Single-Molecule Magnet

The spin relaxation of an Er3+ tetranuclear single-molecule magnet, [Er(hdcCOT)I]4, (hdcCOT = hexahydrodicyclopentacyclooctatetraenide dianion), is modeled as a near-tetrahedral arrangement of Ising-type spins. Combining evidence from single-crystal X-ray diffraction, magnetometry, and computational techniques, the slow spin relaxation is interpreted as a consequence of symmetry restrictions imposed on quantum tunneling within the cluster core. The union of spin and spatial symmetries describe a ground state spin-spin coupled manifold wherein 16 eigenvectors generate the 3D quantum spin-space described by the vertices of a rhombic dodecahedron. Analysis of the experimental findings in this context reveals a correlation between the magnetic transitions and edges connecting cubic and octahedral subsets of the eigenspace convex hull. Additionally, the model is shown to map to a theoretically proposed quantum Cayley network, indicating an underexplored synergy between mathematical descriptions of molecular spin interactions and quantum computing configuration spaces.

A nested spin structure and single molecule magnet behaviour in an Fe8Dy12 heterometallic cyclic coordination cluster

The 20-nuclearity compound [Fe8Dy12(tea)8(teaH)12(NO3)12]·8MeCN (where teaH3 = triethanolamine) was synthesised and characterised through single crystal X-ray diffraction and magnetic measurements. The shape of the magnetic hysteresis in the microSQUID measurements was rationalised using the MAGELLAN program.

Lanthanide Single-molecule Magnets: Synthetic Strategy, Structures, Properties and Recent Advances

Single-molecule magnets (SMMs) show wide potential applications in the field of ultrahigh-density storage materials, quantum computing, spintronics, and so on. Lanthanide (Ln) SMMs, as an important category of SMMs, open up a promising prospect due to their large magnetic moments and huge magnetic anisotropy. However, the construction of high performance for Ln SMMs remains an enormous challenge. Although remarkable advances are focused on the topic of Ln SMMs, the research on Ln SMMs with different nuclear numbers is still deficient. Therefore, this review summarizes the design strategies for the construction of Ln SMMs, as well as the metal skeleton types. Furthermore, we collect reported Ln SMMs with mononuclearity, dinuclearity, and multinuclearity (three or more Ln spin centers) and the SMM properties including energy barrier (U_eff ) and pre-exponential factor (τ₀ ) are described. Finally, Ln SMMs with low-nuclearity SMMs, especially for single-ion magnets (SIMs), are highlighted to understand the correlations between structures and magnetic behavior of the detail SMM properties are described. We expect the review can shed light on the future developments of high-performance Ln SMMs.

Quick and robust PDF data acquisition using a laboratory single-crystal X-ray diffractometer for study of polynuclear lanthanide complexes in solid form and in solution

Self-assembled polynuclear lanthanide hydroxo complexes are important objects in the reticular chemistry approach to the design of various functional materials. Revealing their structure in the solid state and understanding the molecular mechanism of self-assembly in solution require a universal and reliable structural method. Pair distribution function (PDF) analysis is a powerful technique which enables structural insight for a wide range of crystalline and amorphous materials on the nanoscale, but commonly measurements are performed at synchrotron X-ray sources or on specially designed laboratory diffractometers. In the present paper, a standard Bruker D8 QUEST single-crystal X-ray diffractometer equipped with a micro-focus Mo tube and CMOS Photon III detector was adapted to measure PDF data of high quality with Q max = 16.97 Å–1 for solid and liquid samples. An improved data collection strategy and the original data reduction software FormagiX enable calibration and azimuthal full-frame integration of 2D frames, delivering reliable PDFs up to 80 Å with instrumental parameters Q damp = 0.018 Å−1 and Q broad = 0.010 Å−1. The effectiveness of the developed approach was demonstrated with reference samples and real-case studies of tetranuclear lanthanide hydroxocarboxylates in solid form and in solution.

Asymmetric Assembly of Chiral Lanthanide(III) Tetranuclear Cluster Complexes Using Achiral Mixed Ligands: Single-molecule Magnet Behavior and Magnetic Entropy Change

It is challenging to use achiral ligands to spontaneously construct chiral molecular magnets. In this work, two new Ln4 cluster complexes based on N,N'-(1,3-propanediyl)bis[N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]amine] (H6L) have been assembled, which are crystallized in a chiral space group due to the asymmetric distribution of acetate (OAc-) groups and hexafluoroacetylacetonate (F6acac-) groups on both sides of the parallelogram-like Ln4 core. Complex 1, [Dy4(H3L)2(OAc)3(F6acac)3]·5MeOH·2H2O, exhibits single-molecule magnet properties at the zero field with the U eff/k value of 48.4 K; notably, besides the Orbach process, the Raman process is also prominent for the magnetic relaxation of 1. Complex 2, [Gd4(H3L)2(OAc)3(F6acac)3]·4MeOH·2.5H2O, displays a large magnetocaloric effect, whose largest -ΔS m value is 21.88 J kg-1 K-1 (when T = 2 K and ΔH = 5 T); it thus can be utilized as a good magnetic refrigeration molecular material.

A Tetranuclear Dysprosium Schiff Base Complex Showing Slow Relaxation of Magnetization

A tetranuclear dysprosium Schiff base complex was isolated by reacting dysprosium chloride with 2-hydroxy-3-methoxybenzaldehyde and 2-(aminomethyl)pyridine in-situ under basic conditions. The isolated Dy(III) complex was characterized by elemental analyses, single crystal X-ray diffraction and molecular spectroscopy. The complex crystallizes in the triclinic space group P-1 with unit cell parameters of a = 10.2003 (4), b = 13.8602 (5), c = 14.9542 (6), α = 94.523 (3), β = 109.362 (4), and γ = 99.861 (3). The magnetic properties of 1 have been investigated by DC and AC susceptibility measurements. The DC measurements reveal weak exchange coupling of antiferromagnetic nature. In the AC measurement, the complex shows a slow relaxation of magnetization in the absence of an external magnetic field.

A mononuclear nine-coordinated Dy(iii) complex exhibiting field-induced single-ion magnetism behaviour

A new mononuclear Dy(iii) complex, with the formula [Dy(Hcpt)₃]·2H₂O (1), has been successfully prepared via self-assembly between Dy(iii) ions and 2-cyano-N′-(1-(pyridin-2-yl)amido)acetyl (Hcpt) ligand. X-ray diffraction study shows that the Dy(iii) ion is nine-coordinated by three Hcpt ligands with a tridentate chelating mode, leading to an approximately monocapped square-antiprismatic (C_4v) geometry. Magnetic data analysis demonstrates that 1 performs field-induced slow magnetic relaxation with a relaxation barrier of 97.90 K, due to the quantum tunneling effect suppressed upon a static dc field of 2000 Oe. To deeply understand the magnetic behaviors, the relaxation mechanisms and magneto-structure relationship are rationally discussed using ab initio calculations as well.

Reaction of Dy(iii) ion with tridentate acylhydrazone ligand leads to a field-induced Dy(iii) SIM, of which the magneto-structural correlation is elucidated by the magnetic and theoretical studies.

Tetranuclear Hydroxo Complexes of Rare-Earth Elements with the Cubane Core as Products of Self-Controlled Hydrolysis

Abstract

Tetranuclear hydroxo complexes [La4(Deta)4(OH)4(Tfa)3(DetadcH)2](HTfa)(H2O)7(Tfa)3 (I) and [Nd4(Deta)4(OH)4(Tfa)3(DetadcH)2](H2O)n(Tfa)3 (II) with diethylene-N,N′-dicarbamate anions (DetadcH–) are synthesized for the first time by the reactions of lanthanum trifluoroacetate and neodymium trifluoroacetate with a solution of diethylenetriamine (Deta) in air under the self-controlled hydrolysis conditions and are characterized by X-ray diffraction, powder X-ray diffraction, IR spectroscopy, and elemental analysis. Compounds I and II contain the same-type complex cationic fragment with the cubane metal–oxygen core stabilized due to four chelate Deta ligands and two bridging DetadcH– ligands. The DFT calculations of the geometry and vibrational spectrum of the [La4(Deta)4(OH)4(Tfa)3(DetadcH)2]3+ complex cation are performed.

Single molecule magnet behavior and luminescence of {Ln4} and {LnZn} complexes

A serials of tetranuclear coordination clusters [Ln4L2(HL)2(μ3-OH)2(NO3)2](NO3)2 [Ln = Dy (1•3CH3CN•5H2O), Gd (2•4CH3CN•5H2O), H2L = 6,6'-dimethoxy-2,2'-[2,2-dimethylpropane-1,3-diylbis-(nitrilomethylidyne)] diphenol] and dinuclear complexes [LnZnL(NO3)3(H2O)]•2CH3CN [Ln = Dy (3), Er (4), Yb (5), Lu...

Reversible on-off switching of Dy(III) single-molecule magnets via single-crystal-to-single-crystal transformation

While the interest in single-molecule magnets (SMMs) lies in their potential applications in information storage and quantum computing, the switching of their slow magnetic relaxation associated with dynamic crystal-to-crystal transformation...

The first exploration of coordination chemistry using a methyl substituted o-vanillin based ligand: an example starting with Dy4/Zn2Dy2 systems displaying slow relaxation of magnetization

Two butterfly-shaped Dy4 and Zn2Dy2 complexes displaying slow relaxation of magnetization have been synthesized from a new methyl substituted o-vanillin based ligand, enlarging the scope for finding better SMMs.

A Family of Lanthanide Hydroxo Carboxylates with 1D Polymeric Topology and Ln4 Butterfly Core Exhibits Switchable Supramolecular Arrangement

The unique family of coordination polymers [Ln₄(OH)₂(piv)₁₀(H₂O)₂]_∞ of 11 lanthanides (Ln = La-Er) has been prepared by a simple solution method based on controlled hydrolysis. The ribbon-like polymeric structure consisting of connected tetranuclear clusters and supported by pivalate ligands and a framework of H-bonds has been revealed by single-crystal X-ray diffraction. While the compounds demonstrate similar PXRD patterns and unit cell parameters, the joint single-crystal XRD and pair distribution function data suggest the significant local structure change along the lanthanide series. The compounds exist as two packing polymorphs (α and β) with similar ribbon geometry, but different supramolecular arrangement of the ribbons. Dehydration of either polymorph does not disturb the tetranuclear core but leads to a translational symmetry loss along the ribbon and a transformation of the 3D-ordered crystal into a 2D-ordered mesostructure. Rehydration of the mesostructure leads to the β polymorph (except La and Ce), allowing the deliberate switching between the polymorphs via dehydration-rehydration evidenced by means of powder X-ray diffraction, pair distribution function analysis, and density functional theory calculations. Ab initio calculations reveal significant magnetic anisotropy of Ln³⁺ ions with ferro- and antiferromagnetic interactions within tetranuclear [Ln₄(OH)₂(piv)₁₀(H₂O)₂] species. Magnetic susceptibility measurements demonstrated antiferromagnetic coupling, slow magnetic relaxation for Dy, Ho, and Er complexes, and field-induced single-chain magnetism for the Dy compound.

Modulating the slow magnetic relaxation of a mononuclear Dy(iii) single-molecule magnet via a magnetic field and dilution effects

Dynamic magnetic behaviours of a mononuclear Dy(iii) SIM with a square-antiprismatic coordination geometry have been manipulated by using a magnetic field and dilution effects.

Regulating the magnetic dynamics of mononuclear β-diketone Dy(iii) single-molecule magnets through the substitution effect on capping N-donor coligands

Substituent change modulates the coordination symmetries and magnetic dynamics of five mononuclear β-diketonate-Dy(iii) complexes with capping N-donor coligands, which is studied by the combination of magnetic investigation and ab initio calculation.

Lanthanide Metal-Organic Frameworks Assembled from Unexplored Imidazolylcarboxylic Acid: Structure and Field-Induced Two-Step Magnetic Relaxation

A series of 3D homologous metal-organic frameworks, [M(H_0.5L)₂] [M = Dy (1), Ho (2), Yb (3), Sm (4), Gd (5), and Y (6); H₂L = 5-(1H-imidazol-1-yl)isophthalic acid], were isolated. In these complexes, the metal centers behave as hexacoordinated environments with distorted octahedral geometries, which is unusual in the lanthanide series, linking to each other and producing a fascinating 3D architecture. Magnetically, 1 features a field-driven dual-magnetic relaxation, which is rarely observed in high-dimensional coordination polymers. Analysis on the dilution sample (1@Y) and ab initio calculation unveil that the thermally assisted slow relaxation is mostly caused by the single-ion magnetism of Dy^III itself.

Investigating the effect of lanthanide radius and diamagnetic linkers on the framework of metallacrown complexes

By changing the stoichiometric ratios, the one-pot reaction of the glycinehydroxamic acid (H2glyha) ligand with copper(ii) and lanthanide(iii) salts in the presence of diamagnetic [Na2{Fe(CN)5(NO)}] led to two series of isostructural complexes, which can be designated as heterotrimetallic dimeric clusters [{LnCu5(glyha)5}{Fe(CN)5(NO)}(H2O)4]2·xNO3·yH2O (x = 2, y = 11 for La (1), x = 2, y = 11 for Pr (2), and x = 2, y = 11 for Nd (3)) and heterotetrametallic coordination polymers [Na{LnCu5(glyha)5}{Fe(CN)5(NO)}2(H2O)x·yH2O]n (x = 6, y = 4 for Sm (4), x = 6, y = 0 for Gd (5), x = 6, y = 4 for Tb (6), x = 5, y = 5 Dy (7), and x = 6, y = 4 for Ho (8)). Each molecular structure contains LnIII[15-metallacrown-5] nodes and diamagnetic [Fe(CN)5(NO)]2- linkers. The resulting products demonstrate diversified structural frameworks due to the radius effect of LnIII ions and different bridging fashions of diamagnetic [Fe(CN)5(NO)]2- linkers. An analysis of magnetic susceptibilities reveals that 7 exhibits ferromagnetic coupling between CuII and DyIII ions and field-induced SMM behavior.

Dinuclear Lanthanide(III) Complexes Showing Single-Molecule Magnet Behaviour and Optical Properties

Three dinuclear lanthanide(iii) complexes with an acetate bridge, which are synthesised by a Salen-type Schiff base and β-diketonate ligands, i.e. [Ln2L2(TTA)4(OAc)2]·CH2Cl2 (Ln=Eu (1), Gd (2), Dy (3); TTA=thenoyltrifluoroacetonate, H2L=N,N′-ethylenebis(salicylideneimine), are investigated. We obtained the structures of complexes 1–3 by X-ray crystallography. Notably, in terms of the structure of these complexes, what is intriguing is that the acetate groups link two Lniii ions, whereas the cadmium ions do not coordinate. Lanthanide-based luminescence is exhibited by complex 1, which exists in both the solid state and a methanol solution. Through magnetic analysis, it is found that a field-induced single-molecule magnet behaviour is exhibited by complex 3, and the energy barrier is shown to be Ueff=45.97K.

Modulating magnetic dynamics through tailoring the terminal ligands in Dy2 single-molecule magnets

The alternation of terminal ligands leads to distinct arrangements of anisotropy axes and magnetic interactions in two Dy₂ complexes which present different dynamic magnetic behaviors.

Near-infrared luminescence and magnetic properties of dinuclear rare earth complexes modulated by β-diketone co-ligands

The magnetic properties of complexes based on a Schiff base ligand H₂L can be modulated by subtle changes in the coordination environment resulting from changes in the co-ligand substituents.

A new family of dinuclear lanthanide complexes constructed from an 8-hydroxyquinoline Schiff base and β-diketone: magnetic properties and near-infrared luminescence

Six phenoxo-O bridged dinuclear lanthanide(iii) complexes have been assembled utilizing the 2-[(4-nitrophenyl)imino]methyl-8-hydroxyquinoline (HL) and dibenzoylmethane (Hdbm) ligands: [Ln2(dbm)4L2] (Ln = Nd (1), Eu (2), Gd (3), Tb (4), Dy (5) and Er (6)). Complexes 1 and 6 exhibit the characteristic emission peaks of the corresponding Nd3+ and Er3+ ions, respectively. Meanwhile, the excitation wavelength (470 nm) for complex 1 is located in the visible-light region, confirming a practical application value. The studies on magnetic properties reveal that complex 3 features a magnetocaloric effect with a magnetic entropy change of -ΔSm = 14.36 J kg-1 K-1 at 4 K for ΔH = 7 T. What's more, the dynamic magnetic studies for complex 5 show that it exhibits slow magnetic relaxation behavior, typical of SMM behavior, resulting in an energy barrier of ΔE/kB = 75 K with the pre-exponential factor τ0 = 2.2 × 10-7 s. Meanwhile, this research demonstrates that the magnetic properties can be modulated by regulating the electron-donating/withdrawing effects of the substituents on the ligands.

Hybrid Rare-Earth(III)/Bismuth(III) Clusters Assembled with Phosphonates

tert-Butylphosphonic acid and rare-earth precursors are employed to construct four trinuclear rare-earth phosphonate clusters, RE₃( ^tBuPO₃)₂(hfac)₅(CH₃OH)₈]·2CH₃OH (RE = Eu, Y, Pr, and Sm; hfac = hexafluoroacetylacetonate), which are composed of three RE³⁺ ions alternately bridged by two phosphonates. With the introduction of bismuth oxido diketonate, [Bi₉O₇(hfac)₁₃], three different types of rare-earth/bismuth phosphonate clusters, Bi₁₂RE₂ (RE = Pr and Sm), Bi₆Eu₇, and Bi₆Y₉, are successfully obtained via variation of the reaction conditions, and they are the first reported examples of bismuth-oxo clusters encapsulated by cyclic rare-earth-oxo or rare-earth/bismuth-oxo phosphonate clusters, respectively. These clusters show obvious absorption in the UV region, and the Eu-containing clusters exhibit bright-red fluorescence.

Rationally assembled nonanuclear lanthanide clusters: Dy9 displays slow relaxation of magnetization and Tb9 serves as luminescent sensor for Fe3+, CrO42− and Cr2O72−

The utilization of a Schiff base ligand 2-((2-hydroxy-4-methoxy-benzylideneamino)methyl)phenol (H₂L) afforded five nonanuclear lanthanide(iii) clusters. Dy₉ displays slow relaxation of magnetization and Tb₉ serves as luminescent sensor for Fe³⁺, CrO₄²⁻ and Cr₂O₇²⁻.

Syntheses, structures and magnetic properties of macrocyclic Schiff base-supported homodinuclear lanthanide complexes

Five new homodinuclear lanthanide complexes with the general formula [(acac)4Ln2(L)] (Ln3+ = Dy3+ (1), Tb3+ (2), Ho3+ (3), Er3+ (4), and Gd (5)) were synthesized by one-pot [2 + 2] condensation of 2,6-diformyl-4-methylphenol and 1,3-diaminopropane in the presence of various lanthanide acetylacetonates. The eight-coordinate Ln(iii) centre adopts a slightly distorted square antiprism geometry with D4d symmetry. Theoretical analysis and magnetic measurements reveal that the corresponding Dy complex 1 exhibits slow magnetic relaxation behavior, characteristic of a typical SMM with the intramolecular ferromagnetic Dy3+Dy3+ interaction.

Reversible ON-OFF switching of single-molecule-magnetism associated with single-crystal-to-single-crystal structural transformation of a decanuclear dysprosium phosphonate

A decanuclear dysprosium phosphonate (I) undergoes two consecutive SC–SC transformations, associated with OFF–ON–OFF switching of its single-molecule-magnetism.

{Dy₅(EDDC)₂(μ₃-AcO)₂(μ₅-C₁₅H₁₁PO₃)(μ₄-C₁₅H₁₁PO₃)(μ₂-AcO)₂(AcO)₂(H₂O)(CH₃OH)₂}₂(μ₄-C₂O₄)·xH₂O (I), where H₂EDDC is N′,N′′,E,N′,N′′,E-N′,N′′-(ethane-1,2-diylidene)dipyrazine-2-carbohydrazide and C₁₅H₁₁PO₃H₂ is 9-anthrylmethylphosphonic acid, is found to undergo two consecutive single-crystal-to-single-crystal transformations. The first is under UV irradiation (λ = 365 nm for 3 d in air) to {Dy₅(EDDC)₂(μ₃-AcO)₂(μ₅-C₁₅H₁₁PO₃)₂(μ₂-AcO)₂(AcO)₂(H₂O)₃}₂(μ₄-C₂O₄)·xH₂O (I-UV) where the two CH₃OH are replaced by two H₂O and the second by annealing under N₂ at 100 °C on a diffractometer or under Ar in a glovebox to {Dy₅(EDDC)₂(μ₃-AcO)₂(μ₅-C₁₅H₁₁PO₃)₂(μ₂-AcO)₄(H₂O)}₂(μ₄-C₂O₄) (I-A-N₂ or I-A-Ar) where it has lost two H₂O molecules. The second transformation is reversible by exposure to air at room temperature (I-A-N₂-cool). While the overall structures are the same (retaining the space group P2₁/c), there is a considerable expansion of the unit cell from I (8171 ų) to I-UV (8609 ų) and I-A-N₂ (8610 ų) and the coordinations of the Dy atoms undergo major reconstructions. This is associated with switching the single-molecule-magnetism (SMM) from OFF for I to ON for I-UV and to OFF again for I-A-Ar in air. Such a switching mechanism associated with the retention of crystallinity is unique in the chemistry of dysprosium. The structure of the molecule is formed from two symmetry related pentamers joined by an oxalate. A related compound containing two isolated neutral pentamers {Dy₅(EDDC)₂(μ₃-AcO)₂(μ₅-C₁₅H₁₁PO₃)₂(μ₂-AcO)₃(AcO)₂(H₂O)₂}{Dy₅(EDDC)₂(μ₃-AcO)₂(μ₅-C₁₅H₁₁PO₃)(μ₄-C₁₅H₁₁PO₃)(μ₂-AcO)₃(AcO)₂(CH₃OH)₂}·2CHCl₃ (II) has also been isolated with closely related Dy coordination and it exhibits similar SMM behaviour in zero field.

A simple methodology for constructing ferromagnetically coupled Cr(iii) compounds

A large family of chromium(iii) dimers has been synthesised and magneto-structurally characterised using a combination of carboxylate and diethanolamine type ligands. The compounds have the general formula [Cr2(R1-deaH)2(O2CR2)Cl2]Cl where R1 = Me and R2 = H (1), Me (2), CMe3 (3), Ph (4), 3,5-(Cl)2Ph (5), (Me)5Ph (6), R1 = Et and R2 = H (7), Ph (8). The compound [Cr2(Me-deaH)2Cl4] (9) was synthesised in order to study the effect of removing/adding the carboxylate bridge on the observed magnetic behaviour. Direct current (DC) magnetic susceptibility measurements showed ferromagnetic (FM) exchange interactions between the Cr(iii) centres in the carboxylate bridged family with coupling constants in the range +0.37 < J < +8.02 cm-1. Removal of the carboxylate to produce the dialkoxide-bridged compound 9 resulted in antiferromagnetic (AFM) exchange between the Cr(iii) ions. DFT calculations reveal the ferromagnetic exchange is the result of an orbital counter-complementarity effect occuring upon introduction of the bridging carboxylate.