Cyano-Bridged Dy(III) and Ho(III) Complexes with Square-Wave Structure of the Chains

Four new cyano-bridged DyIII-CrIII, DyIII-FeIII, HoIII-CrIII and HoIII-FeIII bimetallic coordination polymers were synthesized by the reaction of [Ln(H2dapsc)(H2O)4](NO3)3 (Ln = Dy, Ho); H2dapsc = 2,6-diacetylpyridinebis(semicarbazone)) with K3[M(CN)6] (M = Cr, Fe) in H2O, resulting in the substitution of two water molecules in the coordination sphere of rare earth by paramagnetic tricharged hexacyanides of Fe and Cr. The complexes are isostructural and consist of alternating [Ln(H2dapsc)(H2O)2]3+ and [M(CN)6]3− units linked by bridges of two cis-cyano ligands of the anion to form square-wave chains. The ac magnetic measurements revealed that the DyCr and DyFe complexes are field-induced single molecule magnets, while their Ho analogs do not exhibit slow magnetic relaxation.

Recent advances in lanthanide coordination polymers and clusters with magnetocaloric effect or single-molecule magnet behavior

Molecular magnetorefrigerant materials for low-temperature magnetic refrigeration and single-molecule magnets for high-density information storage and quantum computing have received extensive attention from chemists and magnetic experts. Lanthanide ions with unique magnetic properties have always been considered as ideal candidates for the construction of such materials. This frontier article focuses on Gd^III-based molecular magnetorefrigerants and lanthanide-based single-molecule magnets and highlights the most significant advances.

Hexanuclear Co4 Dy2 , Zn4 Dy2 , and Co4 Y2 Complexes with Defect Tetracubane Cores: Syntheses, Structures, and Magnetic Properties

A hexanuclear heterometallic cluster of composition [Dy₂ Co₄ (L)₄ (NO₃ )₂ (OH)₄ (C₂ H₅ OH)₂ ] ⋅ 2 C₂ H₅ OH (1) was synthesized by employing a Schiff base 2-(((2-hydroxy-3-methoxybenzyl) imino)methyl)-4-methoxyphenol (H₂ L) as ligand and utilizing Dy(NO₃ )₃  ⋅ 6H₂ O and Co(NO₃ )₂  ⋅ 6H₂ O as metal ion sources. X-ray single-crystal diffraction analysis indicated that complex 1 contains a defect tetracubane core and possesses central symmetric structure, with two Dy^III ions being in the central body position of the molecule and four Co^II ions being arranged at the outer sites. Magnetic studies reveal that complex 1 behaves as single-molecule magnet (SMM) with energy barrier of 27.50 K. To investigate the individual contribution of Dy^III and Co^II ions to the SMM behavior, another two complexes of formulae [Dy₂ Zn₄ (L)₄ (NO₃ )₂ (OH)₄ ] ⋅ 4CH₃ OH (2) and [Y₂ Co₄ (L)₄ (NO₃ )₂ (OH)₄ (C₂ H₅ OH)₂ ] ⋅ 2 C₂ H₅ OH (3) were prepared. Complexes 1 and 3 are isomorphous. The coordination geometries of Dy^III ions in 1 and 2 are different. The Dy^III ions are eight-coordinated in 2 and nine-coordinated in 1. Complex 2 exhibits SMM behavior with energy barrier of 69.67 K, but complex 3 does not display SMM property. These results reveal that the SMM behaviors of 1 and 2 are mainly originated from Dy^III ions. It might be the higher symmetry of Dy^III ions in 2 that results in the higher energy barrier.

Structural Complexity and Magnetic Orderings in a Large Family of 3d-4f Heterobimetallic Sulfates

The synthesis of a large family of heterobimetallic lanthanide copper sulfates was realized via stoichiometric hydrothermal reactions among Ln₂O₃, CuO, and H₂SO₄, giving rise to four distinct phases, namely Ln₂Cu(SO₄)₂(OH)₄ (Ln = Sm-Ho) (LnCuSO₄-1), Ln₄Cu(SO₄)₂(OH)₁₀ (Ln = Tm-Lu) (LnCuSO₄-2), LnCu(SO₄)(OH)₃ (Ln = Nd-Gd, except Pm) (LnCuSO₄-3), and LnCu(SO₄)(OH)₃ (Ln = Dy-Lu) (LnCuSO₄-4), with completely different topologies. The passage from LnCuSO₄-1 and LnCuSO₄-3 to LnCuSO₄-2 and LnCuSO₄-4 across the 4f series, respectively, can be ascribed to the effect of lanthanide contraction, which progressively induces shrinking of the Ln-O distance, reduction in the Ln coordination number, and eventually structural transitions. The incorporation of identical 3d-4f metal ions into different spin-lattices, in conjunction with substitution of diverse Ln³⁺ cations within the same spin-lattice, gives rise to tunable magnetic properties varying from ferromagnetic ordering in GdCuSO₄-3 and HoCuSO₄-4 to antiferromagnetic ordering in YbCuSO₄-4, and to paramagnetic correlations found in GdCuSO₄-1 and YbCuSO₄-2.

The Influence of Halide Substituents on the Structural and Magnetic Properties of Fe6Dy3 Rings

We report the synthesis and magnetic properties of three new nine-membered Fe(III)-Dy(III) cyclic coordination clusters (CCCs), with a core motif of [Fe₆Dy₃(μ-OMe)₉(vanox)₆(X-benz)₆] where the benzoate ligands are substituted in the para-position with X = F (1), Cl (2), Br (3). Single crystal X-ray diffraction structure analyses show that for the smaller fluorine or chlorine substituents the resulting structures exhibit an isostructural Fe₆Dy₃ core, whilst the 4-bromobenzoate ligand leads to structural distortions which affect the dynamic magnetic behavior. The magnetic susceptibility and magnetization of 1-3 were investigated and show similar behavior in the dc (direct current) magnetic data. Additional ac (alternating current) magnetic measurements show that all compounds exhibit frequency-dependent and temperature-dependent signals in the in-phase and out-of-phase component of the susceptibility and can therefore be described as field-induced SMMs. The fluoro-substituted benzoate cluster 1 shows a magnetic behavior closely similar to that of the corresponding unsubstituted Fe₆Dy₃ cluster, with U_eff = 21.3 K within the Orbach process. By increasing the size of the substituent toward 4-chlorobenzoate within 2, an increase of the energy barrier to U_eff = 36.1 K was observed. While the energy barrier becomes higher from 1 to 2, highlighting that the introduction of different substituents on the benzoate ligand in the para-position has an impact on the magnetic properties, cluster 3 shows a significantly different SMM behavior where U_eff is reduced in the Orbach regime to only 4.9 K.

Coordination control of a semicarbazide Schiff base ligand for spontaneous aggregation of a Ni2Ln2 cubane family: influence of ligand arms and carboxylate bridges on the organization of the magnetic core

A new family of tetranuclear [Ni₂Ln₂O₄] cubane complexes has been assembled from carbazido ligand by altering the 4f ions without changing the core topology, which provided weak ferromagnetic and antiferromagnetic interactions.

Modulating the structural topologies and magnetic relaxation behaviour of the Mn–Dy compounds by using different auxiliary organic ligands

A MnIII4Dy^III complex and a one-dimensional chain containing MnIII2Dy^III units have been obtained by using different combinations of organic ligands, and a slow magnetic relaxation behavior was observed for both complexes.

Self-assembled octanuclear [Ni5Ln3] (Ln = Dy, Tb and Ho) complexes: synthesis, coordination induced ligand hydrolysis, structure and magnetism

Octanuclear NiII5LnIII3 complexes obtained with ligand H₂L show ferromagnetic interactions for Ni₅Dy₃ and Ni₅Tb₃ while antiferromagnetic interactions for Ni₅Ho₃.

The different magnetic relaxation behaviors in [Fe(CN)6]3− or [Co(CN)6]3− bridged 3d–4f heterometallic compounds

For the isomorphic tetranuclear 3d–4f compounds constructed by [M(CN)₆]³⁻ linking Ln^III-Schiff-base units, the diamagnetic Co^III ions in the system could suppress QTM effectively and obtain a field-induced SMMs behavior.

Regulation of magnetic relaxation behavior by replacing 3d transition metal ions in [M2Dy2] complexes containing two different organic chelating ligands

Two [MIII2DyIII2] complexes (M = Fe for 1 and Co for 2) with mixed organic ligands were obtained. Complex 2 exhibits single molecule magnet behavior with U_eff = 64.0(9) K.

Heterometallic MIILnIII (M = Co/Zn; Ln = Dy/Y) Complexes with Pentagonal Bipyramidal 3d Centers: Syntheses, Structures, and Magnetic Properties

We herein reported the syntheses, structures, and magnetic properties of three dinuclear heterometallic M^IILn^III complexes, namely, [M^IILn^III(H₂L)(CH₃OH)₂(NO₃)₂](NO₃)·S (M = Co, Ln = Dy, S = MeOH (1_CoDy); M = Zn, Ln = Dy, S = MeOH (2_ZnDy); M = Co, Ln = Y, S = MeNO₂ (3_CoY), H₄L = 2,6-diacetylpyridine bis[2-(semicarbazono) propionylhydrazone]. Synthesized from the predesigned multidentate ligand H₄L, which has two different coordination pockets (smaller N₃O₂ and larger N₂O₄ pockets) suitable for either a 3d or a 4f metal center, all these complexes have very similar structures, where the M^II centers possess a pentagonal bipyramidal (PBP) geometry and the Ln^III sites have a tetradecahedron geometry. Magnetic measurements on these compounds revealed the existence of weak ferromagnetic coupling between the Co²⁺ and Dy³⁺ centers and the field-induced slow magnetic relaxation of all three complexes. Furthermore, theoretical calculation on all these complexes indicates that although the change of the diamagnetic Zn²⁺ ion to the paramagnetic Co²⁺ ion only slightly modifies the local magnetic anisotropy of the Dy³⁺ ion, the weak Co-Dy magnetic interaction decreases the energy barrier. These compounds are the first systematic results of a heterometallic 3d-4f single-molecule magnet containing predesigned PBP 3d metal ions.

Transformative 3d-4f coordination cluster carriers

The aim of this perspective is to summarise the use of the reported 3d-4f Coordination Clusters (CCs) in catalytic reactions and to demonstrate the potential of this emerging field. The pioneering work of Shibasaki, Matsunaga and others, demonstrated the use of 3d-4f in situ systems to catalyse asymmetric organic transformations. Our recent studies show that well characterised 3d-4f CCs catalyse numerous organic transformations and useful mechanistic aspects of their catalysis can be obtained. Furthermore, we have shown that by manipulation of the metal ion coordination environment; the nature of the 3d and lanthanide ions and the organic periphery of the ligand can all improve the efficacy of a 3d-4f CC catalyst. All in situ formed and well characterized 3d-4f CCs involved in catalysis are discussed.

Targeted replacement: systematic studies of dodecanuclear {MLn} coordination clusters (M = Cr, Co; Ln = Dy, Y)

Three dodecanuclear 3d-4f coordination clusters, [CrIII6LnIII6(μ3-OH)8(tbdea)6(C6H5COO)16]·2H2O (Ln = Dy (1), Y (2)) and [CoIII6DyIII6(μ3-OH)8(nbdea)6(m-CH3C6H4COO)16]·2H2O·2CH3CN (3), have been synthesized under solvothermal conditions and characterized. Single-crystal X-ray diffraction analysis revealed that all three compounds possess an analogous {MIII6LnIII6} core (M = Cr, Co; Ln = Dy, Y) and dc magnetic susceptibility studies indicated that the magnetic exchange couplings between DyIII ions are dominant antiferromagnetic, while the CrIII-DyIII interactions are weakly ferromagnetic. Furthermore, the ac magnetic susceptibility measurements showed that both CrIII6DyIII6 compound 1 and CoIIi6DyIII6 compound 3 containing highly anisotropic DyIII ions displayed single-molecule magnetic (SMM) behavior with the energy barrier Ueff increasing from 12.8 K (for 1) to 20.8 K (for 3), indicating that weak 3d-4f exchange couplings enhance the QTM and reduce the energy barrier.

New field-induced single ion magnets based on prolate Er(iii) and Yb(iii) ions: tuning the energy barrierUeffby the choice of counterions within an N3-tridentate Schiff-base scaffold

Counterions modulate the structure and magnetic properties of rarely observed high-coordinate SIM species.

Influence of alcoholic solvent and acetate anion coordination mode variations on structures and magnetic properties of heterometallic Zn2Dy2 tetranuclear clusters

We clarify that slight modifications of the synthetic conditions generate two Zn₂Dy₂ clusters with acetate anion coordination mode variation and different magnetic behaviors.

2D carboxylate-bridged LnIII coordination polymers: displaying slow magnetic relaxation and luminescence properties in the detection of Fe3+, Cr2O72− and nitrobenzene

Carboxylate-bridged Ln-CPs were obtained. 1-Dy shows slow magnetic relaxation. 1-Eu (or 1-Tb) exhibits multifunctional luminescence properties i.e., detecting Fe³⁺, Cr₂O₇²⁻ and nitrobenzene.