Recent advances in dysprosium-based single molecule magnets: Structural overview and synthetic strategies

Elucidating the Impact of Rare Earth or Transition Metal Identity on the Physical and Electronic Structural Properties of a Series of Redox-Active Tris(amido) Complexes

The use of redox-active ligands with the f-block elements has been employed to promote unique chemical transformations and explore their unique emergent electronic properties for a myriad of applications. In this study, we report eight new tris(amido) metal complexes: 1-Ln (Ln = Tb3+, Dy3+, Ho3+, Er3+, Tm3+, and Yb3+), 1-La, and 1-Ti (an early transition metal analogue). The one-electron oxidation of the tris(amido) ligand was conducted to generate semi-iminato complexes 2-Ln, 2-La, and 2-Ti, and these complexes were studied using EPR. Tris(amido) complexes 1-Ln, 1-La, and 1-Ti were fully characterized using a range of spectroscopic (NMR and UV-vis/NIR) and physical techniques (X-ray diffraction and cyclic voltammetry, with the exception of 1-La). Computational methods were employed to further elucidate the electronic structures of these complexes. Lastly, complexes 1-Ln, 1-La, and 1-Ti were probed as catalysts for alkyl-alkyl cross-coupling, and the initial rate of the reaction was measured to explore the influence of the metal ion.

Spin dynamics phenomena of a cerium(III) double-decker complex induced by intramolecular electron transfer

Switchable spin dynamic properties in single-molecule magnets (SMMs) via an applied stimulus have applications in single-molecule devices. Many SMMs containing heavy lanthanoid ions with strong uniaxial magnetic anisotropy have been reported to exhibit SMM characteristics in the absence of an external magnetic field. On the other hand, SMMs containing light lanthanoid cerium(III) (Ce3+) ions exhibit field-induced slow magnetic relaxation. We investigated the chemical conversion of a diamagnetic Ce4+ ion (4f0) to a paramagnetic Ce3+ ion (4f1) in Ce-phthalocyaninato double-decker complexes (TBA+[Ce(obPc)2]- (1) and TBA+[Ce(Pc)2]- (2)) which exhibit field-induced SMM behaviour due to a 4f1 system. The phthalocyaninato ligands with electron-donating substituents (obPc2- = 2,3,9,10,16,17,23,24-octabutoxyphthalocyaninato) in 1 have a significant effect on the valence state of the Ce ion, which is reflected in its magnetic properties due to the mixed valence state of the Ce ion. Given that Ce double-decker complexes with π-conjugated ligands undergo intramolecular electron transfer (IET) to the Ce ion mixed valence state, characterised by a mixture of 4f0 and 4f1 configurations, we examined the dynamic disorder inherent in IET influencing magnetic relaxation.

Eight-coordinate mono- and dinuclear Dy(III) complexes containing a rigid equatorial plane and an anisobidentate carboxylate ligand in the axial position: synthesis, structure and magnetism

A rigid pentadentate chelating ligand (H2L) has been utilized to synthesize a series of octacoordinate mononuclear complexes, [Dy(L)(Ph3PO)(OOCR)] (where R = C6H5 (1), C(CH3)3 (2), CF3 (3)) and a dinuclear complex, [Dy2(L)2(Ph3PO)2{(OOC)2C6H4}] (4) based on the highly anisotropic Dy(III) ion. All the complexes were structurally characterized by single-crystal X-ray diffraction studies. The complexes were formed by the coordination action of the dianionic pentadentate ligand [L]2-, one phosphine oxide, and carboxylate ligands. DC and AC magnetic measurements were performed on 1-4. Complexes 1-4 show SMM behaviour, under zero DC field for 1 and 4, and under 500 Oe and 1000 Oe DC fields for 2 and 3 respectively, with thermally activated, Raman, and Raman and quantum tunnelling dominant relaxation mechanisms for 1 and 2, 3 and 4, respectively.

Single-Molecule Magnet Behavior of Confined Dy(III) in a Mixed Heteroatom-Substituted Polyoxotungstate

Two heteroatom-templated Dy(III)-confined polyoxotungstates [H2N(CH3)2]7Na7[Dy2(H2O)7(W4O9)(HPSeW15O54)(α-SeW9O33)2]·31H2O (1) and [H2N(CH3)2]14K2Na18{[Dy2(H2O)13W14O40]2[α-SeW9O33]4[HPSeW15O54]2}·44H2O (2) were synthesized by a one-pot aqueous reaction and structurally characterized. The most distinctive structural feature of complexes 1 & 2 is the simultaneous presence of both trivacant Keggin [α-SeW9O33]8- and Dawson [HPSeW15O54]10- building blocks containing P(III)-Se(IV) heteroatoms. The trimeric polyanion of 1 can be represented as a fusion of two trivacant Keggin [α-SeW9O33]8- and Dawson [HPSeW15O54]10- building units encapsulating the [Dy2(H2O)7(W4O9)]12+ cluster. On the other hand, hexameric polyoxoanions of 2 are described as four trivacant Keggin [α-SeW9O33]8- and two Dawson [HPSeW15O54]10-, building units anchoring a [Dy4(H2O)26W28O80]20+ cluster. The magnetic investigation revealed the presence of significant magnetic anisotropy and slow relaxation of magnetization behavior for complex 1 with a phenomenological energy barrier, Ueff = 13.58 K in the absence of an external magnetic field, and Ueff = 24.57 K in the presence of a 500 Oe external dc magnetic field. On the other hand, complex 2 favors the QTM relaxation process in the absence of an external magnetic field and shows field-induced slow relaxation of magnetization with Ueff = 11.11 K at 1500 Oe applied dc field. The in-depth analysis of magnetic relaxation dynamics shows that the relaxation process follows the Orbach as well as Raman relaxation pathways. Further, the ab initio calculation of the studied complexes confirms that the highly axial ground and first excited energy states (containing pure highest mJ states) are responsible for the observed single-molecule magnet (SMM) behavior. Remarkably, this is the first example of a mixed heteroatom-based Dy(III)-substituted polyoxotungstate with both trimeric Keggin [α-SeW9O33]8- and Dawson [HPSeW15O54]10- building units showing SMM behavior.

The prediction of single-molecule magnet properties via deep learning

This paper uses deep learning to present a proof-of-concept for data-driven chemistry in single-molecule magnets (SMMs). Previous discussions within SMM research have proposed links between molecular structures (crystal structures) and single-molecule magnetic properties; however, these have only interpreted the results. Therefore, this study introduces a data-driven approach to predict the properties of SMM structures using deep learning. The deep-learning model learns the structural features of the SMM molecules by extracting the single-molecule magnetic properties from the 3D coordinates presented in this paper. The model accurately determined whether a molecule was a single-molecule magnet, with an accuracy rate of approximately 70% in predicting the SMM properties. The deep-learning model found SMMs from 20 000 metal complexes extracted from the Cambridge Structural Database. Using deep-learning models for predicting SMM properties and guiding the design of novel molecules is promising.

Alkyl chain length influence of the functionalized diethanolamine ligand on the slow relaxation of the magnetization in {CoIII3DyIII3} complexes

We report the synthesis, structural characterization and magnetic properties of a series of Co(III)/Dy(III) complexes built up from an N-alkyl derivatized amino-alcohol ligand diethanolamine, functionalized with CnH2n+1 alkyl chains (n = 3, 4, 6, 8 and 10). While n = 3 afforded a butterfly {CoIII2DyIII2} core, the other alkyl chains (n = 4, 6, 8) afforded hexanuclear triangle-in-triangle {CoIII3DyIII3} complexes as shown by single-crystal X-ray determinations. Infrared spectroscopy allows us to characterize the C10 derivative complex, which did not crystallize. Magnetic ac susceptibility data collected below 10 K at driving frequencies up to 10 kHz under zero-dc field and up to 1 T provide insight into the SMM behaviour of the studied complexes. The characteristic time of the magnetization dynamics can be understood in terms of the competing Raman, Direct and Orbach-like mechanisms. A relationship between the magnetization dynamics within the family of complexes and the increasing alkyl chain length is discussed.

Origin of Weak Magnetic Coupling in a Dimanganese(II) Complex Bridged by the Tetrathiafulvalene-Tetrathiolate Radical

Magnetic exchange coupling (J) between different spin centers plays a crucial role in molecule-based magnetic materials. Direct exchange coupling between an organic radical and a metal is frequently stronger than superexchange through diamagnetic ligands, and the strategy of using organic radicals to engender desirable magnetic properties has been an area of active investigation. Despite significant advances and exciting bulk properties, the magnitude of J for radical linkers bridging paramagnetic centers is still difficult to rationally predict. It is thus important to elucidate the features of organic radicals that govern this parameter. Here, we measure J for the tetrathiafulvalene-tetrathiolate radical (TTFtt3-•) in a dinuclear Mn(II) complex. Magnetometry studies show that the antiferromagnetic coupling in this complex is much weaker than that in related Mn(II)-radical compounds, in contrast to what might be expected for the S-based chelating donor atoms of TTFtt. Experimental and computational analyses suggest that this small J coupling may be attributed to poor overlap between Mn- and TTFtt-based magnetic orbitals coupled with insignificant spin density on the coordinating S-atoms. These factors override any expected increase in J from the comparatively strong S-donors. This work elucidates the magnetic coupling properties of the TTFtt3-• radical for the first time and also demonstrates how multiple competing factors must be considered in rationally designing organic radical ligands for molecular-based magnetic compounds.

LnIII/MnII-LnIII complexes derived from a salicylic azo dye ligand: synthesis, structures, magnetic and fluorescence properties

Two LnIII complexes Ln(HTMSA)3(H2O)2·5.5H2O (Ln = Dy (1) and Tb (2), H2TMSA = 5-azotriazolyl-3-methoxysalicylaldehyde) and two MnII-LnIII clusters [Mn(H2O)6][MnLn2(TTMSA)4(HTTMSA)2(H2O)6]·4H2O (Ln = Dy (3) and Tb (4), H2TTMSA = 5-azotetrazolyl-3-methoxysalicylaldehyde) have been synthesized and structurally characterized. Single-crystal X-ray diffraction reveals that 1 and 2 are isostructural complexes in which the LnIII ions are surrounded by six oxygen atoms from three chelate HTMSA ligands and two oxygen atoms from two coordinated water molecules forming a distorted square-anti-prismatic geometry. In complexes 3 and 4, the MnII ions adjust two LnIII mononuclear anion clusters into tri-nuclear LnIII-MnII-LnIII anion clusters, with an additional [Mn(H2O)6]2+ as a counter ion to maintain the electroneutrality of the compound. Magnetic studies reveal that all the complexes 1-4 show nonzero out-of-phase signals, indicating single-molecule magnet behavior. The photoluminescence spectra of all the complexes were investigated and are discussed in detail.

A Pair of Multifunctional Cu(II)-Dy(III) Enantiomers with Zero-Field Single-Molecule Magnet Behaviors, Proton Conduction Properties and Magneto-Optical Faraday Effects

Multifunctional materials with a coexistence of proton conduction properties, single-molecule magnet (SMM) behaviors and magneto-optical Faraday effects have rarely been reported. Herein, a new pair of Cu(II)-Dy(III) enantiomers, [DyCu2(RR/SS-H2L)2(H2O)4(NO3)2]·(NO3)·(H2O) (R-1 and S-1) (H4L = [RR/SS] -N,N'-bis [3-hydroxysalicylidene] -1,2-cyclohexanediamine), has been designed and prepared using homochiral Schiff-base ligands. R-1 and S-1 contain linear Cu(II)-Dy(III)-Cu(II) trinuclear units and possess 1D stacking channels within their supramolecular networks. R-1 and S-1 display chiral optical activity and strong magneto-optical Faraday effects. Moreover, R-1 shows a zero-field SMM behavior. In addition, R-1 demonstrates humidity- and temperature-dependent proton conductivity with optimal values of 1.34 × 10-4 S·cm-1 under 50 °C and 98% relative humidity (RH), which is related to a 1D extended H-bonded chain constructed by water molecules, nitrate and phenol groups of the RR-H2L ligand.

Hilbert Space in Isotopologue Dy(III) SMM Dimers: Dipole Interaction Limit in [163/164Dy2(tmhd)6(tape)]0 Complexes

Single-molecule magnets are molecular complexes proposed to be useful for information storage and quantum information processing applications. In the quest for multilevel systems that can act as Qudits, two dysprosium-based isotopologues were synthesized and characterized. The isotopologues are [164Dy2(tmhd)6(tape)] (1(I=0)) and [163Dy2(tmhd)6(tape)] (2(I=5/2)), where tmhd = 2,2,6,6-tetramethylheptandionate and tape = 1,6,7,12-tetraazaperylene. Both complexes showed slow relaxation at a zero applied magnetic field with dominant Orbach and Raman relaxation mechanisms. μSQUID studies at milli-Kelvin temperatures reveal quasi-single ion loops, in contrast with the expected S-shape (near zero field) butterfly loops, characteristic of antiferromagnetically coupled dimeric complexes. Through analysis of the low-temperature data, we find that the interaction operating between Dy(III) is small, leading to a small exchange biasing from the zero-field transition. The resulting indirectly coupled nuclear states are degenerate or possess a small energy difference between them. We, therefore, conclude that for the creation of Qudits with enlarged Hilbert spaces, shorter Dy(III)···Dy(III) distances are deemed essential.

Regulating Magnetic Relaxations of Cyano-Bridged {DyIII MoV } Systems by Tuning the N-Sites in β-Diketone Ligands

Cyano-bridged 4d-4f molecular nanomagnets have re-called increasing research interests in molecular magnetism since they offer more possibilities in achieving novel nanomagnets with versatile structures and magnetic interactions. In this work, four β-diketone ligands bearing different substitution N-sites were designed and synthesized, namely 1-(2-pyridyl)-3-(3-pyridyl)-1,3-propanedione (HL1 ), 1,3-Bis (3-pyridyl)-1,3-propanedione (HL2 ), 1-(4-pyridyl)-3-(3-pyridyl)-1,3-propanedione (HL3 ), and 1,3-Bis (4-pyridyl)-1,3-propanedione (HL4 ), to tune the magnetic relaxation behaviors of cyano-bridged {DyIII MoV } systems. By reacting with DyCl3  ⋅ 6H2 O and K4 Mo(CN)8  ⋅ 2H2 O, four cyano-bridged complexes, namely {[Dy[MoV (CN)8 ](HL1 )2 (H2 O)3 ]} ⋅ 6H2 O (1), {[Dy[MoV (CN)8 ](HL2 )(H2 O)3 (CH3 OH)]}2  ⋅ 2CH3 OH ⋅ 3H2 O (2), {[Dy[MoV (CN)8 ](HL3 )(H2 O)2 (CH3 OH)] ⋅ H2 O}n (3), and {[Dy[MoV (CN)8 ](HL4 )2 (H2 O)3 ]} ⋅ 2H2 O⋅CH3 OH (4) were obtained. Structural analyses revealed that 1 and 4 are binuclear complexes, 2 has a tetragonal structure, and 3 exhibits a stair-like polymer chain structure. The DyIII ions in all complexes have eight-coordinated configurations with the coordination spheres DyO7 N1 for 1 and 4, DyO6 N2 for 2, and DyO5 N3 for 3. Magnetic measurements indicate that 1 is a zero-field single-molecule magnet (SMM) and complexes 2-4 are field-induced SMMs, with complex 4 featuring a two-step relaxation process. The magnetic characterizations and ab initio calculations revealed that changing the N-sites in the β-diketone ligands can effectively alter the structures and magnetic properties of cyano-bridged 4d-4f nanomagnets by adjusting the coordination environments of the DyIII centers.

Creation of a Field-Induced Co(II) Single-Ion Magnet by Doping into a Zn(II) Diamagnetic Metal-Organic Framework

The combination of single-ion magnets (SIMs) and metal-organic frameworks (MOFs) is expected to produce new quantum materials. The principal issue to be solved in this regard is the development of new strategies for the synthesis of SIM-MOFs. This work demonstrates a new simple strategy for the synthesis of SIM-MOFs where a diamagnetic MOF is used as the framework into which the SIM sites are doped. 1, 0.5, and 0.2 mol% of the Co(II) ions are doped into the Zn(II) sites of [CH6 N3 ][ZnII (HCOO)3 ]. The doped Co(II) sites in the MOFs perform as SIM with a positive D term of zero-field splitting. The longest magnetic relaxation time is 150 ms (0.2 mol% Co) at 1.8 K under a static field of 0.1 T. Temperature dependency of the relaxation time suggests suppressing magnetic relaxation by reduction of spin-spin interaction upon doping in the rigid framework. Thus, this work represents a proof of concept for the creation of a single-ion doped magnet in the MOF. This simple synthetic strategy will be widely applied for the creation of quantum magnetic materials.

[α-AsW9O33]9- bridged hexagonal clusters of Ln(III) showing field induced SMM behavior: experimental and theoretical insight

Polyoxometalates (POM), as inorganic polydentate oxygen donors, provide binding opportunities for oxophilic lanthanide metal centers to construct novel Ln-substituted POM materials with exciting structures and attractive properties. Herein, we have reported four arsenotungstate [α-AsW₉O₃₃]^9- based lanthanide-containing polyoxometalates [Cs_xK_36-x{Ln₆(H₂O)₁₂(α-AsW₉O₃₃)₆}]·yH₂O (Ln = Er (1), Gd (2), Ho (3), and Tb (4)), which are synthesized in an alkaline medium. Complexes 1-3 are the dimeric structures of [Ln₃(H₂O)₆(α-AsW₉O₃₃)₃]^18- polyanions, whereas complex 4 is a hexamer of the polyanion [Tb (H₂O)₂(α-AsW₉O₃₃)]^6- as a building unit. In all the complexes, [α-AsW₉O₃₃]^9- units are staggered up and down and give rise to the chair conformation, where one [α-AsW₉O₃₃]^9- unit bridges two Ln(III) centers through four μ₂-oxygen and two terminal oxygen atoms, resulting in the hexagonal arrangement of lanthanides. The dynamic magnetic measurement indicates that only complex 1 exhibits slow relaxation of magnetization with an applied dc field (1500 Oe). To gain insight into the slow relaxation of magnetization in complex 1, the ligand-field parameters and the splitting of the ground-state multiplet of the Er(III) ions have been estimated. The ab initio calculation results confirm that the ground state wave function of these molecules (1, 3, and 4) is mainly composed of a mixture of m_J states, and the non-axial crystal field (CF) terms are more predominant than the axial CF term. The solid-state fluorescence spectra of 1-4 reveal that the photoexcitation O → M ligand-to-metal charge-transfer (LMCT) of arsenotungstate fragments is effectively quenched due to the spatial coordination environment around the Ln(III) ion.

A Combined Synthetic, Magnetic, and Theoretical Study on Enhancing Ligand-Field Axiality for Dy(III) Single-Molecule Magnets Supported by Ferrocene Diamide Ligands

Molecular design is crucial for improving the performance of single-molecule magnets (SMMs). For dysprosium(III) SMMs, enhancing ligand-field axiality is a well-suited strategy to achieve high-performance SMMs. We synthesized a series of dysprosium(III) complexes, (NN^TIPS)DyBr(THF)₂ (1, NN^TIPS = fc(NSiⁱPr₃)₂; fc = 1,1'-ferrocenediyl, THF = tetrahydrofuran), [(NN^TIPS)Dy(THF)₃][BPh₄] (2), (NN^TIPS)DyI(THF)₂ (3), and [(NN^TBS)Dy(THF)₃][BPh₄] (4, NN^TBS = fc(NSi^tBuMe₂)₂), supported by ferrocene diamide ligands. X-ray crystallography shows that the rigid ferrocene backbone enforces a nearly axial ligand field with weakly coordinating equatorial ligands. Dysprosium(III) complexes 1-4 all exhibit slow magnetic relaxation under zero fields and possess high effective barriers (U_eff) around 1000 K, comparable to previously reported (NN^TBS)DyI(THF)₂ (5). We probed the influences of structural variations on SMM behaviors by theoretical calculations and found that the distribution of negative charges defined by r_q, i.e., the ratio of the charges on the axial ligands to the charges on the equatorial ligands, plays a decisive role. Moreover, theoretical calculations on a series of model complexes 1'-5' without equatorial ligands unveil that the axial crystal-field parameters B₂⁰ are directly proportional to the N-Dy-N angles and support the hypothesis that enhancing the ligand-field axiality could improve SMM performance.

Recent Progress for Single-Molecule Magnets Based on Rare Earth Elements

Single-molecule magnets (SMMs) have attracted much attention due to their potential applications in molecular spintronic devices. Rare earth SMMs are considered to be the most promising for application owing to their large magnetic moment and strong magnetic anisotropy. In this review, the recent progress in rare earth SMMs represented by mononuclear and dinuclear complexes is highlighted, especially for the modulation of magnetic anisotropy, effective energy barrier (U_eff) and blocking temperature (T_B). The terbium- and dysprosium-based SMMs have a U_eff of 1541 cm^-1 and an increased T_B of 80 K. They break the boiling point temperature of liquid nitrogen. The development of the preparation technology of rare earth element SMMs is also summarized in an overview. This review has important implications and insights for the design and research of Ln-SMMs.

High-stability spherical lanthanide nanoclusters for magnetic resonance imaging

High-nuclear lanthanide clusters have shown great potential for the administration of high-dose mononuclear gadolinium chelates in magnetic resonance imaging (MRI). The development of high-nuclear lanthanide clusters with excellent solubility and high stability in water or solution has been challenging and is very important for expanding the performance of MRI. We used N-methylbenzimidazole-2-methanol (HL) and LnCl3·6H2O to synthesize two spherical lanthanide clusters, Ln32 (Ln = Ho, Ho32; and Ln = Gd, Gd32), which are highly stable in solution. The 24 ligands L- are all distributed on the periphery of Ln32 and tightly wrap the cluster core, ensuring that the cluster is stable. Notably, Ho32 can remain highly stable when bombarded with different ion source energies in HRESI-MS or immersed in an aqueous solution of different pH values for 24 h. The possible formation mechanism of Ho32 was proposed to be Ho(III), (L)- and H2O → Ho3(L)3/Ho3(L)4 → Ho4(L)4/Ho4(L)5 → Ho6(L)6/Ho6(L)7 → Ho16(L)19 → Ho28(L)15 → Ho32(L)24/Ho32(L)21/Ho32(L)23. To the best of our knowledge, this is the first study of the assembly mechanism of spherical high-nuclear lanthanide clusters. Spherical cluster Gd32, a form of highly aggregated Gd(III), exhibits a high longitudinal relaxation rate (1 T, r1 = 265.87 mM-1·s-1). More notably, compared with the clinically used commercial material Gd-DTPA, Gd32 has a clearer and higher-contrast T1-weighted MRI effect in mice bearing 4T1 tumors. This is the first time that high-nuclear lanthanide clusters with high water stability have been utilized for MRI. High-nuclear Gd clusters containing highly aggregated Gd(III) at the molecular level have higher imaging contrast than traditional Gd chelates; thus, using large doses of traditional gadolinium contrast agents can be avoided.

Strategies to quench quantum tunneling of magnetization in lanthanide single molecule magnets

Enhancing blocking temperature (T_B) is one of the holy grails in Single Molecule Magnets(SMMs), as any future potential application in this class of molecules is directly correlated to this parameter. Among many factors contributing to a reduction of T_B value, Quantum Tunnelling of Magnetisation (QTM), a phenomenon that is a curse or a blessing based on the application sought after, tops the list. Theoretical tools based on density functional and ab initio CASSCF/RASSI-SO methods have played a prominent role in estimating various spin Hamiltonian parameters and establishing the mechanism of magnetization relaxation in this class of molecules. Particularly, various strategies to quench QTM effects go hand-in-hand with experiments, and different methods proposed to quell QTM effects are scattered in the literature. In this perspective, we have explored various approaches that are proposed in the literature to quench QTM effects, and these include the role of (i) local symmetry of lanthanides, (ii) super-exchange interaction in {3d-4f} complexes, (iii) direct-exchange interaction in {radical-4f} and metal-metal bonded complexes to suppress the QTM, (iv) utilizing external stimuli such as an electric field or pressure to modulate the QTM and (v) avoiding QTM effects by stabilising toroidal states in 4f and {3d-4f} clusters. We believe the strategies summarized here will help to design new-generation SMMs.

Intramolecular Ferromagnetism in Di-Nuclear 3 d-Transition-Metal Single-Molecule Magnets by Pseudo-Serial Arrangement

Di-nuclear citrate complexes, [CH₆ N₃ ]₂ [M₂ (citH)₂ (H₂ O)₄ ] ⋅ 2H₂ O (citH₄ =citric acid; M=Fe^II (Fe-2), Co^II (Co-2), and Ni^II (Ni-2)), are synthesized. The ligand, citH^3- , is deprotonated only at the three carboxy groups, which is different from the previously reported tetra-nuclear structures with cit^4- ligands. Magnetic measurements reveal that these complexes have intramolecular ferromagnetism with J=∼0 cm^-1 (Ni-2), 0.02 cm^-1 (Co-2), and 0.04 cm^-1 (Fe-2). Co-2 and Fe-2 show slow magnetic relaxation, and are field-induced SMMs with activation energy of spin-reversal U_eff =27 cm^-1 (Co-2) and 4.2 cm^-1 (Fe-2). Density functional theory calculations indicate that the uniaxial anisotropy along the z-axis of each metal ion center forms the pseudo-serial arrangement, leading to intramolecular ferromagnetism via the magnetic dipole interaction. This work demonstrates the creation of ferromagnetic SMMs by the magnetic dipole engineering of 3d di-nuclear metal ion centers.

Role of molecular symmetry in the magnetic relaxation dynamics of five-coordinate Dy(III) complexes

A new family of low-coordinate mononuclear Dy^III single-molecule magnets [(Trapen^TMS)Dy(L^B)] (Trapen = tris(2-aminobenzyl)amine; TMS = SiMe₃; L^B = THF 1, pyridine 2, ONMe₃3) has been synthesized and structurally characterized by single crystal X-ray diffraction. The five-coordinate Dy^III ions exhibit distorted triangular bipyramidal geometries, among the different neutral ligands L^B on the apex and the same Trapen^TMS ligand, making the pyramid base of the trigonal bipyramid. Magnetic data analysis reveals that 1-3 are characteristic of SMM behaviors without a dc field, accompanying an unambiguous quantum tunneling of magnetization. Under an extra dc field of 500 Oe, field-induced slow magnetic relaxation behaviors occur with Raman and/or QTM processes. Ab initio calculations were also performed to rationalize the observed discrepancy in the magnetic behaviors, and the result illustrates that the SMM behavior could be effectively manipulated by the axial symmetry of the triangular bipyramidal Dy^III motifs.

Combined experimental and theoretical studies on a series of mononuclear LnIII single-molecule magnets: dramatic influence of remote substitution on the magnetic dynamics in Dy analogues

A series of Ln^III complexes of general formula [Ln(H₂L¹)₂(NO₃)₂(H₂O)](NO₃) (1-5) [Ln = Dy (1), Tb (2) Ho (3), Er (4), and Yb (5)] and an analogous Dy^III complex with ligand H₂L², [Dy(H₂L²)₂(NO₃)₃(H₂O)](NO₃) (6), where H₂L¹ and H₂L² stand for (E)-2-[(2-hydroxyphenyl)iminomethyl]-6-methoxy-4-methylphenol and (E)-2-[(2-hydroxy-5-methylphenyl)iminomethyl]-6-methoxy-4-methylphenol, respectively, have been synthesized and magneto-structurally characterized. All these complexes are isostructural and isomorphous, in which the zwitterionic form of the ligands predominantly coordinate the metal centers. The magnetic study revealed that complex 3 displays negligible SMM behaviour, while 1 and 6 are zero field SMMs, the performance of which can largely be improved in the presence of an applied dc field by lowering under barrier relaxation processes, and finally 2, 4, and 5 are field-induced SMMs. The most remarkable observation in the present study is the dramatically-enhanced SMM performance in 6 compared to 1, achieved by only a remote methyl substitution at the ligand framework to increase the intermolecular separation. Although SINGLE_ANISO ab initio calculations for 1 and 6 are very similar, the POLY_ANISO module revealed weak dipolar interactions in both the compounds but significant antiferromagnetic interaction in 1, thereby justifying the experimental fact. The present work discloses that even a small substitution such as a methyl group can adequately increase the intermolecular separation, leading to several-fold enhanced effective energy barrier.

Synthesis, structures and magnetic properties of four dysprosium-based complexes with a multidentate ligand with steric constraint

Four dysprosium-based complexes with a multidentate ligand with steric constraint were constructed. Their structures and magnetic properties were studied.

Axial Ligand as a Critical Factor for High-Performance Pentagonal Bipyramidal Dy(III) Single-Ion Magnets

The choice of axial ligands is of great importance for the construction of high-performance Dy-based single-molecule magnets (SMMs). Here, combining axial ligands Ph₃SiO^- (anion of triphenylsilanol) and 2,6-dichloro-4-nitro-PhO^- (the anion of 2,6-dichloro-4-nitrophenol) with a neutral macrocyclic ligand 2,14-dimethyl-3,6,10,13,19-pentaazabicyclo[13.3.1]nonadeca-1(19),2,13,15,17-pentaene (L₂^N5) generates two new pentagonal bipyramidal Dy(III) complexes [Dy^III(L₂^N5) (X)₂](BPh₄) (X = Ph₃SiO^-, 1; 2,6-dichloro-4-nitro-PhO^-, 2) with strong axial ligand fields. Magnetic characterizations show that 1 possesses a large energy barrier above 1000 K and a magnetic hysteresis up to 9 K, whereas 2 only displays field-induced peaks of alternating-current susceptibilities without the hysteresis loop, even though 2 has a similar coordination geometry with 1. Detailed Ab initio calculations indicate an apparent difference in the axial negative charge between both complexes, which is caused by the diverse electron-donating properties of the axial ligands. The present work provides an efficient strategy to enhance the SMMs' properties, which highlights that the electron-donating property of the axial ligands is especially important for constructing the high-performance Dy-based SMMs.

Anion-Manipulated Hydrolysis Process Assembles of Giant High-Nucleation Lanthanide-Oxo Cluster

Widespread concern has been raised over the synthesis of highly nucleated lanthanide clusters with special shapes and/or specific linkages. Construction of lanthanide clusters with specific shapes and/or linkages can be achieved by carefully regulating the hydrolysis of lanthanide metal ions and the resulting hydrolysis products. However, studies on the manipulation of lanthanide-ion hydrolysis to obtain giant lanthanide-oxo clusters have been few. In this study, we obtained a tetraicosa lanthanide cluster (3) by manipulating the hydrolysis of Dy(III) ions using an anion (OAc^-). As far as we know, cluster 3 has the highest nucleation among all lanthanide-oxo clusters reported. In 3, two triangular Dy₃O₄ are oriented in opposite directions to form the central connecting axis Dy₆(OH)₈, which is in turn connected to six Dy₃O₄ that are oriented in different directions. Meanwhile, a sample of a chiral trinuclear dysprosium cluster (1) was obtained in a mixed CH₃OH and CH₃CN solvent and by replacing the anion in the reaction to Cl^- ions. In this cluster, 1,3,4-thiadiazole-2,5-diamine (L²) is free on one side through π···π interactions and is parallel to the o-vanillin (L¹)^- ligand, thus resulting in a triangular arrangement. The arrangement of L² affects the end group coordination in the cluster 1 structure through hydrogen bonding and induces the cluster to exhibit chirality. When the reaction solvent was changed to CH₃OH, a sample of cluster 2, composed of two independent triangular Dy₃ that have different end group arrangements, was obtained. Magnetic analysis showed that clusters 1 and 3 both exhibit distinctive single-molecule magnetic properties under zero-magnetic-field conditions. This study thus provides a method for the creation of chiral high-nucleation clusters from achiral ligands and potentially paves the way for the synthesis of high-nucleation lanthanide clusters with unique forms.

Structure and Properties of Heterometallics Based on Lanthanides and Transition Metals with Methoxy-β-Diketonates

The possibility of obtaining volatile polynuclear heterometallic complexes containing lanthanides and transition metals bound by methoxy-β-diketonates was studied. New compounds were prepared by cocrystallization of monometallic complexes from organic solvents. Ln(tmhd)₃ were used as initial monometallic complexes (Ln = La, Pr, Sm, Gd, Tb, Dy, Lu; tmhd = 2,2,6,6-tetramethylheptane-3,5-dionate) in combination with TML₂ in various ratios (TM = Cu, Co, Ni, Mn; L: L¹ = 1,1,1-trifluoro-5,5-dimethoxypentane-2,4-dionate, L² = 1,1,1-trifluoro-5,5-dimethoxy-hexane-2,4-dionate, L³ = 1,1,1-trifluoro-5-methoxy-5-methylhexane-2,4-dionate). Heterometallic complexes of the composition [(LnL₂tmhd)₂TM(tmhd)₂] were isolated for light lanthanides Ln= La, Pr, Sm, Gd, and L= L¹ or L². By single crystal XRD, it has been established that heterometallic compounds containing La, Pr, Cu, Co, and Ni are isostructural linear coordination polymers of alternating mononuclear transition metal complexes and binuclear heteroleptic lanthanide complexes, connected by donor-acceptor interactions between oxygen atoms of the methoxy groups and transition metal atoms. A comparison of powder XRD patterns has shown that all heterometallic complexes obtained are isostructural. Havier lanthanides Ln = Tb, Dy, Lu did not form heterometallics. Instead, homometallic complexes Ln(L³)₃ were identified for Ln = Dy, Lu as well as for Ln = La. The thermal properties of the complexes were investigated by TG-DTA and vacuum sublimation tests. The heterometallic complexes were found to be not volatile and decomposed under heating to produce inorganic composites of TM oxides and Ln fluorides. In contrast, Ln(L³)₃ is volatile and may be sublimed in a vacuum. Results of magnetic measurements are discussed for several heterometallic and homometallic complexes.

Alkali metal-linked triangular building blocks assemble a high-nucleation lanthanoid cluster based on single-molecule magnets

The metallic central magnetic axes in high-nucleation clusters with complex structural connections tend to be disorganized and cancel each other out. Therefore, high-nucleation clusters cannot easily exhibit single-molecule magnets (SMMs) behaviors. Herein, we select a triple-core building block (Dy3K2, 1) and use linked diamagnetic alkali metal to form an open, spherical, high-nucleation cluster Dy12Na6 (3) with SMM behavior. Furthermore, by changing the reaction conditions, Dy6K2 (2) formed by linking two Dy3 by K(I) is obtained. High-resolution electrospray mass spectrometry of clusters 1-3 effectively captures the building block Dy3, and clusters 1 and 3 and Dy3 have high stability even with the increase in ion source energy. To the best of our knowledge, this is the first time that an SMM based on a high-nucleation cluster has been obtained by connecting magnetic primitives via diamagnetic metal ions. Dy12K6 is currently the highest nuclear ns-4f heterometallic SMM.

An Effective Strategy of Introducing Chirality to Achieve Multifunctionality in Rare-Earth Double Perovskite Ferroelectrics

The hybrid rare-earth double perovskite (HREDP) system provides great convenience for the construction of multifunctional materials. However, suffering from the high symmetry of their intrinsic structure, HREDPs face the challenges in the realization and optimization of ferroelectric and piezoelectric properties. For the first time, after a systematic investigation of the chirality transformation principle, it is found that the introduction of chirality is an efficient strategy for the targeted construction of multifunctionality, which simultaneously increases the possibility of obtaining multiaxial ferroelectricity and ferroelasticity, and effectively realizes a large piezoelectric response. Moreover, chirality induced ferroelasticity will also achieve excellent magnetic or optical response driven by pressure-sensitive. To verify the feasibility of the above ideas, by using rare-earth ions (Ce³⁺ ) and suitable chiral organic cations, a new HREDP, (R-N-methyl-3-hydroxylquinuclidinium)₂ RbCe(NO₃ )₆ (R1) is successfully designed, in which ferroelasticity, multiaxial ferroelectricity, satisfactory piezoelectric response, and the pressure-driven single-ion magnetics switch are simultaneously achieved for the first time. This work shows that the induction of chirality and the HREDP system provide an effective strategy and ideal platform for the expansion and optimization of the functions in perovskite ferroelectrics.

Subcomponent self-assembly of circular helical Dy6(L)6 and bipyramid Dy12(L)8 architectures directed via second-order template effects

In situ metal-templated (hydrazone) condensation also called subcomponent self-assembly of 4,6-dihydrazino-pyrimidine, o-vanillin and dysprosium ions resulted in the formation of discrete hexa- or dodecanuclear metallosupramolecular Dy6(L)6 or Dy12(L)8 aggregates resulting from second-order template effects of the base and the lanthanide counterions used in these processes. XRD analysis revealed unique circular helical or tetragonal bipyramid architectures in which the bis(hydrazone) ligand L adopts different conformations and shows remarkable differences in its mode of metal coordination. While a molecule of trimethylamine acts as a secondary template that fills the void of the Dy6(L)6 assembly, sodium ions take on this role for the formation of heterobimetallic Dy12(L)8 by occupying vacant coordination sites, thus demonstrating that these processes can be steered in different directions upon subtle changes of reaction conditions. Furthermore, Dy6(L)6 shows an interesting spin-relaxation energy barrier of 435 K, which is amongst the largest values within multinuclear lanthanide single-molecular magnets.

Self-assembly of octanuclear Ln(III)-based clusters: their large magnetocaloric effects and highly efficient conversion of CO2

The design and construction of high-nuclear lanthanide clusters with fascinating topology and functional properties have been an active area of research, however, the development of an effective approach for obtaining high-nuclear lanthanide clusters with multifunctional properties is still extremely difficult. Up to now, a systematic approach for guiding the further expansion of Ln(III)-based clusters showing good functional properties is lacking. Herein, we design and synthesize a polydentate Schiff base ligand (HL), which reacts with β-diketonate salts Ln(acac)₃·2H₂O, and a series of Ln₈ clusters [Ln₈(acac)₆(L)₂(μ₃-O)₆(μ₂-C₂H₅O)₄(μ₂-Hacac)₂]·2CH₃CN (Ln(III) = Gd (1), Dy (2), and Ho (3); HL = pyridine-2-carboxylic acid (5-hydroxymethyl-furan-2-ylmethylene)-hydrazide, Hacac = acetylacetone) have been successfully synthesized. Single-crystal X-ray diffraction studies reveal that clusters 1-3 are isostructural and can be viewed as a Ln₈ core bridged by eighteen μ₂-O atoms, six μ₃-O atoms and two μ₄-O atoms. Magnetic studies show that cluster 1-Gd8 displays a large magnetocaloric effect with -ΔS_m = 46.14 J kg^-1 K^-1 (T = 2.0 K and ΔH = 7.0 T); cluster 2-Dy8 exhibits single-molecule magnet behavior under zero-field conditions. It is worth mentioning that the -ΔS_m of cluster 1-Gd8 is larger than that of most reported polynuclear Gd(III)-based clusters; the 2-Dy8 cluster is one of the rare polynuclear Ln_n SMMs (n ≥ 8) under zero dc field. Importantly, these Ln(III)-based clusters (1-3) can catalyze the cycloaddition of CO₂ with epoxides with high efficiency under mild conditions; and cluster 1-Gd8 as a catalyst could be reused at least three times without obvious loss of catalytic performance.

Self-assembly of fish-bone and grid-like CoII-based single-molecule magnets using dihydrazone ligands with NNN and NNO pockets

Three Co^II complexes, [Co₂(H₂L¹)₂](ClO₄)₄·4CH₃OH (1), [Co₂(H₄L²)₂](ClO₄)₄ (2) and [Co₄(H₄L²)₄](ClO₄)₈ (3), were constructed by the self-assembly of the symmetrical dihydrazone ligands H2L1 and H4L2 with Co^II ions under different synthetic conditions. The fish-bone-like complex 1 was obtained using the ligand H2L1 in methanol via the solvothermal method, while the self-assembly of H4L2 with Co^II ions is solvent-dependent, producing the fish-bone-like complex 2 and [2 × 2] grid-like complex 3. Magnetic susceptibility measurements and theoretical calculations reveal that the large negative D values for the three complexes stem from their easy-axis magnetic anisotropy. Ac magnetic susceptibility measurements disclosed field-induced slow magnetic relaxation behaviors and the presence of Raman and/or direct processes of the three complexes at various applied dc fields.

Rigid N3O2-Pentadentate Ligand-Assisted Octacoordinate Mononuclear Ln(III) Complexes: Syntheses, Characterization, and Slow Magnetization Relaxation

A series of air-stable mononuclear octacoordinate Ln(III) complexes, [(L)Ln(TPPO)₃]OTf (Ln = Y (1·Y); Gd (1·Gd); Tb (1·Tb); Dy (1·Dy); Ho (1·Ho); and Er (1·Er)) and [(L)Ln(TPPO)(NO₃)] (Ln = Y (2·Y) and Dy (2·Dy)), are synthesized employing a rigid N₃O₂-pentadentate chelating ligand as the basis ligand and meridional ancillary ligands (where H₂L = 2,6-diacetylpyridine bis-benzoylhydrazone, TPPO = triphenylphosphine oxide, and OTf^- = trifluoromethanesulfonate). All the complexes are synthesized under aerobic conditions and characterized comprehensively by spectroscopic and X-ray crystallographic techniques. Magnetic property investigation on the polycrystalline solid samples of 1·Ln (Ln = Gd, Tb, Dy, Ho, and Er) and 2·Dy are reported. A field-induced single-molecule magnet behavior was observed for the Dy derivatives. 1·Dy exhibits the highest effective energy barrier of magnetization reversal, U _eff/k _B = 47 K under H _dc = 1 kOe among the complexes presented herein.

Fluoride-bridged dinuclear dysprosium complex showing single-molecule magnetic behavior: supramolecular approach to isolate magnetic molecules

Using Na-encapsulated benzo[18]crown-6 (Na)(B18C6) as a counter cation, we successfully magnetically isolated a fluoride-bridging Dy dinuclear complex {[(PW11O39)Dy(H2O)2]2F} (Dy2POM) with lacunary Keggin ligands. (Na)(B18C6) formed two types of tetramers through C-H⋯O, π⋯π and C-H⋯π interactions, and each tetramer aligned in one dimension along the c-axis to form two types of channels. One channel was partially penetrated by a supramolecular cation from the ±a-axis direction, dividing the channel in the form of a "bamboo node". Dy2POM was spatially divided by this "bamboo node," which magnetically isolated one portion from the other. The temperature dependence of the magnetic susceptibility indicated a weak ferromagnetic interaction between the Dy ions bridged by fluoride. Dy2POM exhibited the magnetic relaxation characteristics of a single-molecule magnet, including the dependence of AC magnetic susceptibility on temperature and frequency. Magnetic relaxation can be described by the combination of thermally active Orbach and temperature-independent quantum tunneling processes. The application of a static magnetic field effectively suppressed the relaxation due to quantum tunneling.

Single-molecule nano-optoelectronics: insights from physics

Single-molecule optoelectronic devices promise a potential solution for miniaturization and functionalization of silicon-based microelectronic circuits in the future. For decades of its fast development, this field has made significant progress in the synthesis of optoelectronic materials, the fabrication of single-molecule devices and the realization of optoelectronic functions. On the other hand, single-molecule optoelectronic devices offer a reliable platform to investigate the intrinsic physical phenomena and regulation rules of matters at the single-molecule level. To further realize and regulate the optoelectronic functions toward practical applications, it is necessary to clarify the intrinsic physical mechanisms of single-molecule optoelectronic nanodevices. Here, we provide a timely review to survey the physical phenomena and laws involved in single-molecule optoelectronic materials and devices, including charge effects, spin effects, exciton effects, vibronic effects, structural and orbital effects. In particular, we will systematically summarize the basics of molecular optoelectronic materials, and the physical effects and manipulations of single-molecule optoelectronic nanodevices. In addition, fundamentals of single-molecule electronics, which are basic of single-molecule optoelectronics, can also be found in this review. At last, we tend to focus the discussion on the opportunities and challenges arising in the field of single-molecule optoelectronics, and propose further potential breakthroughs.

Slow magnetic relaxation in a Dy3 triangle and a bistriangular Dy6 cluster

Two lanthanide single-molecule magnets (SMMs) [Dy₃(μ₃-OH)(HL-1)₃(H₂O)₃](NO₃)₂·3H₃O (1, H₃L-1 = (E)-3-(((8-hydroxyquinolin-2-yl)methylene)amino)propane-1,2-diol) and [Dy₆(μ₃-OH)₄(H₂L-2)₄(HL-2)₂(L-2)₂] (2, H₃L-2 = (E)-2-hydroxy-N'-(2-hydroxy-3-methoxybenzylidene)benzohydrazide) were synthesized and characterized structurally and magnetically. Complex 1 contains a triangular Dy₃ core in which the three Dy³⁺ ions share a μ₃-OH^- anion and the deprotonated ligands of (HL-1)^2- serve both capping and bridging functions, while 2 displays a centrosymmetric hexanuclear Dy^III structure with two similar Dy₃ triangular cores ligated by two fully deprotonated (L-2)^3- ligands, each of which shares two μ₃-OH^- anions. All the Dy^III ions are eight-coordinated with quasi D_2d or C_2v symmetry. Magnetic studies reveal that 1 exhibited two-step magnetic relaxation under an applied dc field of 800 Oe, with effective energy barriers of 40.1 and 31.0 K for the slow relaxation (SR) and fast relaxation regimes (FR), respectively. Meanwhile, 2 only showed a tail of slow magnetic relaxation at above 2 K. Ab initio calculations have been carried out to show the nature of their different magnetic properties.

Giant Crown-Shaped Dy34 Nanocluster with High Acid-Base Stability Assembled by an out-to-in Growth Mechanism

Lanthanoid metal ions have large ionic radii, complex coordination modes, and easy distortion of coordination spheres, but the design and synthesis of high-nucleation lanthanoid clusters with high stability in solution (especially aqueous solution) are challenging. Herein, a diacylhydrazone ligand (H₂L¹) with multidentate chelating coordination sites was used to react with Dy(OAc)₃·4H₂O under solvothermal conditions to obtain an example of a 34-nucleus crown-shaped dysprosium cluster [Dy₃₄(L)₈(μ₂-OH)(μ₃-OH)₂₁(μ₃-O)₁₄(OAc)₃₁(OCH₃)₂(H₂O)₁₅](OAc)₃ (1). Structural analysis showed that the bisacylhydrazone ligand H₂L¹ with polydentate chelate coordination sites could rapidly capture Dy^III ions, thereby forming 34-nucleus crown-shaped dysprosium cluster 1 following the out-to-in growth mechanism. Cluster 1 remained stable after immersion in solutions with different pH values (3-14) for 24 h. To the best of the authors' knowledge, high-nucleation lanthanoid clusters with excellent strong acid and base stability and water stability are very rare. Meanwhile, high-resolution electrospray mass spectrometry molecular ion peaks produced by cluster 1 were captured, which proved to be stable also in organic solvents. Magnetic research showed that cluster 1 exhibited frequency-dependent behavior. This work provides a new idea for designing and synthesizing high-nucleation lanthanoid clusters with high stability.

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.

Series of the Largest Dish-Shaped Dysprosium Nanoclusters Formed by In Situ Reactions

A three-dimensional supermolecule structure is easily formed due to the diverse coordination modes of high-oxidation-state lanthanide metal ions. However, the design and construction of zero-dimensional (0 D) dish-shaped high-nuclearity lanthanide clusters are difficult. Herein, for the first time, we synthesized a series of the largest dish-shaped high-nuclearity lanthanide nanoclusters (1-4) by in situ tandem reactions under solvothermal one-pot conditions. The formation of 1 and 2 involved an in situ reaction of aldehydes and amines, while the condensation reactions between aldehydes occurred in 3 and 4. Based on the structural characteristics of the dish-shaped lanthanide clusters, we proposed two possible assembly mechanisms involving Dy₁ → Dy₇ → Dy₁₃ → Dy₁₉ (planar epitaxial growth mechanism) and Dy₁ → Dy₁₂ → Dy₁₈ → Dy₁₉ (planar internal growth mechanism).

Alkali Metal Based Triimidosulfite Cages as Versatile Precursors for Single-Molecule Magnets

Based on the potassium [{S(tBuN)2 (tBuNH)}2 K3 (tmeda)-K3 {(HNtBu)(NtBu)2 S}2 ] (1) and sodium precursors [S(tBuN)3 (thf)3 -Na3 SNa3 (thf)3 (NtBu)3 S] (2), [S(tBuN)3 (thf)3 Na3 {(HNtBu)(NtBu)2 S}] (3) and [(tmeda)3 S-{Na3 (NtBu)3 S}2 ] (4) the syntheses and magnetic properties of three mixed metal triimidosulfite based alkali-lanthanide-metal-cages [(tBuNH)Dy{K(0.5tmeda)}2 {(NtBu)3 S}2 ]n (5) and [ClLn{Na(thf)}2 {(NtBu)3 S}2 ] with Ln=Dy (6), Er (7) are reported. The corresponding potassium (1) and sodium (2-4) based cages are characterized through XRD and NMR experiments. Preventing lithium chloride co-complexation led to a significant increase of SMM performance to previously reported sulfur-nitrogen ligands. The subsequent DyIII -complexes 5 and 6 display slow relaxation of magnetization at zero field, with relaxation barriers U=77.0 cm-1 for 5, 512.9 and 316.3 cm-1 for 6, respectively. Significantly, the latter complex 6 also exhibits a butterfly-shaped hysteresis up to 7 K.

Magnetooptical Properties of Lanthanide(III) Metal-Organic Frameworks Based on an Iridium(III) Metalloligand

Integrating magnetic and optical properties into a metal-organic framework (MOF) remains a great challenge. Herein, we have reasonably constructed two 3D magnetooptical MOFs by incorporating a [Ir^III(ppy)₂(bpy)]⁺-based fluorescent metalloligand and magnetic Ln^III centers. The alternating arrangements of Δ- or Λ-[Ir^III(ppy)₂(bpy)]⁺ endow these MOFs with enhanced optical properties. Moreover, the use of Dy^III leads to field-induced slow magnetic relaxation. This work provides an effective strategy for the preparation of magnetooptical bifunctional MOFs.

Toroidal versus centripetal arrangement of the magnetic moment in a Dy4 tetrahedron

Magnetic investigation and ab initio calculations reveal toroidal arrangement of the magnetic moment rather than centripetal anisotropies in a tetrahedral Dy4 complex.