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

Chiral Co3Y Propeller-Shaped Chemosensory Platforms Based on 19F-NMR

Two propeller-shaped chiral Co^III₃Y^III complexes built from fluorinated ligands are synthesized and characterized by single-crystal X-ray diffraction (SXRD), IR, UV-vis, circular dichroism (CD), elemental analysis, thermogravimetric analysis (TGA), electron spray ionization mass spectroscopy (ESI-MS), and NMR (¹H, ¹³C, and ¹⁹F). This work explores the sensing and discrimination abilities of these complexes, thus providing an innovative sensing method using a ¹⁹F NMR chemosensory system and opening new directions in 3d/4f chemistry. Control experiments and theoretical studies shed light on the sensing mechanism, while the scope and limitations of this method are discussed and presented.

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.

Synthesis, structural characterization, and magnetic property study of {Cr3Ln3}, Ln = Gd and Dy complexes

We have successfully prepared and structurally characterized triangle-in-triangle {Cr₃Ln₃} complexes with Ln = Gd and Dy employing alcohol-amine, N-methyldiethanolamine (H₂mdea) and pivalate ligands. These complexes and the Yttrium analogue proved to be isostructural and crystallized in a P₁ triclinic cell. DC and AC magnetic measurements were carried out and supported by quantum computations at DFT and CASSCF levels. DC magnetic data are dominated by the Cr(III)-Ln(III) antiferromagnetic interaction and by single-ion anisotropy in the case of the Dy(III) complex. Ln(III)-Ln(III) magnetic interactions are negligible, as well as Cr(III)-Cr(III) ones. From AC data, slow relaxation of the magnetization is observed at 0 DC applied magnetic field in the case of the Dy(III) complex below 4 K. From temperature and field dependence data, possible Raman and Orbach relaxation mechanisms are established in the absence of quantum tunnelling pathways, suggesting a successful suppression of the latter due to the Cr(III)-Dy(III) exchange interaction.

A new family of decanuclear Ln7Cr3 clusters exhibiting a magnetocaloric effect

Two dimeric Ln–Cr clusters with formula {Ln(H₂O)₈[Ln₆Cr₃(L)₆(CH₃COO)₆(μ₃-OH)₁₂(H₂O)₁₂]}·(ClO₄)₆·xH₂O (Ln = Gd, x = 35 for 1 and Ln = Dy, x = 45 for 2, HL = 2-pyrazinecarboxylic acid) were obtained by a ligand-controlled hydrolytic method with a mixed ligand system (2-pyrazinecarboxylic acid and acetate). Single crystal structure analysis showed that two trigonal bipyramids of [Gd₃Cr₂(μ₃-OH)₆]⁹⁺ worked as building blocks in constructing the metal-oxo cluster core of [Gd₆Cr₃(μ₃-OH)₁₂]¹⁵⁺ by sharing a common top – a Cr³⁺ ion. Additionally, compound 1 forms a three-dimensional framework with a one-dimensional nanopore channel along the a-axis through a hydrogen-bond interaction between the cationic cluster core and the free mononuclear cation [Gd(H₂O)₈]³⁺ and the π-bond interactions of the pyrazine groups on the two cationic cluster cores. Magnetic calculations indicated a weak ferromagnetic coupling interaction for Gd⋯Gd and Gd⋯Cr in compound 1, with its magnetic entropy change (−ΔS_m) reaching 21.1 J kg⁻¹ K⁻¹ at 5 K, 7 T, while compound 2 displayed an obvious frequency-dependency at H_dc = 2000 Oe.

Two decanuclear Ln–Cr clusters Ln₇Cr₃ were obtained, which formed a three-dimensional framework with one-dimensional nanopore channel through hydrogen-bond and π-bond interactions. Gd₇Cr₃ had a magnetic entropy change of 21.1 J kg⁻¹ K⁻¹ at 5 K, 7 T.

A Series Three-Dimensional Ln4Cr4 (Ln = Gd, Tb, Er) Heterometallic Cluster-Based Coordination Polymers Containing Interesting Nanotubes Exhibiting High Magnetic Entropy

A series of novel 3D 3d-4f heterometallic cluster-based coordination polymers, [Ln₄Cr₄(μ₃-O)₄(μ₄-O)₄(NA)₈(H₂O)₁₂]·xH₂O (Ln = 1-Gd, 2-Tb, 3-Er; HNA = nicotinic acid; x = 13 (1-Gd), 11.33 (2-Tb), 15 (3-Er)), have been successfully synthesized by hydrothermal method using nicotinic acid as bridging ligand. The single-crystal X-ray diffraction (SCXRD) analysis indicated that the basic unit of Ln₄Cr₄ shows a butterfly-shaped structure. Furthermore, each Ln₄Cr₄ cluster connects with other four Ln₄Cr₄ clusters by bridging NA^- ligands to form a 3D structure containing interesting 1D honeycomb-shaped coordination nanotubes. The variable temperature magnetic susceptibility measurements of compound 1 revealed that the existence of antiferromagnetic (AF) coupling between the metal ions in the Gd₄Cr₄ clusters. Field-dependent isothermal magnetization studies displayed that the magnetic entropy change (-ΔS_m) value of 1-Gd reached 22.05 J K^-1 kg^-1.

Trigonal bipyramidal CoDy3 cluster exhibiting single-molecule magnet behavior

A heterometallic 3d-4f compound formulated as {[CoIII2Dy3Na(CH3CH2COO)6(OH)6(NO3)4(H2O)2]·H2O}n (1) has been synthesized and structurally characterized. The Co2Dy3 metal core adopts trigonal bipyramidal (TBP) geometry. Compound 1 displays single-molecule magnet behavior with an energy barrier of 60.3 K under a zero dc field.

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.

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.

Two rare Cr–Ln (Ln = Dy, Tb) heterometallic cluster substituted polyoxometalates featuring hexameric aggregates: hydrothermal syntheses, crystal structures and magnetic studies

Two hexameric Cr–Ln cluster substituted POMs have been obtained under hydrothermal conditions. They represent the first examples of 3d–4f heterometallic cluster substituted POMs incorporating Cr–Ln clusters.

Incorporating polyoxometalates and organic ligands to pursue 3d–4f heterometallic clusters: a series of {Cr4Ln4} clusters stabilized by phthalic acid and [SiW12O40]4−

By introduction of trilacunary Keggin-type polyoxometalate to the hydrothermal reaction system of Cr³⁺, Ln³⁺ and phthalic acid, a series of novel {Cr₄Ln₄} heterometallic clusters with the formula Cs₂[Cr₄Ln₄(μ₄-O)₄(μ₃-O)₄(C₈H₄O₄)₄(H₂O)₁₂](H₃SiW₁₂O₄₀)Cl·23H₂O (1-Ln, Ln = Ce, Pr, Nd) and [Cr₄Ln₄(μ₄-O)₄(μ₃-O)₄(C₈H₄O₄)₄(H₂O)₁₀](H₆SiW₁₂O₄₀)Cl₂·18H₂O (2-Ln, Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er) have been obtained. Single-crystal structural analyses show that 1-Ln and 2-Ln constitute the first cases of Cr–Ln heterometallic clusters stabilized by inorganic polyoxometalate anions and organic ligands. Optical spectra studies demonstrate that 1-Ln and 2-Ln are narrow-gap semiconductors with band gaps of about 1.5 eV. Magnetic investigation shows that compound 2-Dy is a potential single molecule magnet.

By introduction of trilacunary Keggin-type polyoxometalate to the hydrothermal reaction system of Cr³⁺, Ln³⁺ and phthalic acid, a series of novel {Cr₄Ln₄} heterometallic clusters have been obtained.

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.