Syntheses, Structures, and Properties of High-Nuclear 3d−4f Clusters with Amino Acid as Ligand: {Gd6Cu24}, {Tb6Cu26}, and {(Ln6Cu24)2Cu} (Ln= Sm, Gd)

Modulation of Magnetic Anisotropy and Exchange Interaction in Phenoxide-Bridged Dinuclear Co(II) Complexes

We report a new class of four dimeric Co(II) complexes [Co₂(bbpen)(X)₂] (H₂bbpen = N,N'-bis(2-hydroxybenzyl)-N,N'-bis(2-methylpyridyl)ethylenediamine) [X^- = SCN (1), Cl (2), Br (3), and I (4)] with different coordination geometry of two Co(II) centers (trigonal-prismatic and pseudo-tetrahedral) and their magnetic study. Interestingly, the two Co(II) centers show two different types of magnetic anisotropy. State of the art ab initio CASSCF analysis reveals that the six-coordinate or the trigonal-prismatic Co(II) center possesses a consistently large negative axial zero-field splitting (negative D) parameter (∼-60 cm^-1), while the four-coordinate or the pseudo-tetrahedral Co(II) center exhibits a range of D values from +13 to -23 cm^-1. Ab initio calculations employing the lines model were used to estimate the magnetic exchange as both the Co(II) centers possess significant magnetic anisotropy. All the complexes display rare ferromagnetic interaction, and the strength of this interaction decreases as the ligand field on the pseudo-tetrahedral Co(II) center decreases from SCN^- > Cl^- > Br^- > I^-.

Oximato-Based Ligands in 3 d/4 f-Metal Cluster Chemistry: A Family of {Cu3Ln} Complexes with a "Propeller"-like Topology and Single-Molecule Magnetic Behavior

The organic chelating and bridging ligands 9,10-phenanthrenedione-9-oxime (phenoxH) and 9,10-phenanthrenedione-9,10-dioxime (phendoxH₂) were synthesized and subsequently employed for the first time in heterometallic 3 d/4 f-metal cluster chemistry. The general reaction between CuCl₂·2H₂O, LnCl₃·6H₂O, phenoxH, and NEt₃ in a 1:2:2:4 molar ratio, in a solvent mixture comprising MeCN and MeOH, afforded brown crystals of a new family of [Cu₃LnCl₃(phenox)₆(MeOH)₃] clusters (Ln = Gd (1), Tb (2), Dy (3)) that possess an unprecedented [Cu₃Ln(μ-NO)₆]³⁺ "propeller"-like core. Complexes 1-3 are the first {Cu₃Ln} clusters in which the outer Cu^II and the central Ln^III atoms are solely bridged by diatomic oximato bridges. The {Cu-N-O-Ln} bridging units are very distorted with torsion angles spanning the range 35.5-48.9° and 25.2-55.6° in 1 and 2, respectively. As a result, complexes 1-3 are antiferromagnetically coupled, in agreement with previously reported magnetostructural criteria for oximato-bridged Cu/Ln complexes. The magnetic susceptibility data for all complexes were nicely fit to an isotropic spin Hamiltonian (for 1) or a Hamiltonian that accounts for the spin of the Cu^II atoms, the spin component of the Ln^III, the spin-orbit coupling (λ), an axial ligand-field component around the Ln^III atoms (Δ), and the Zeeman effect (for the anisotropic 2 and 3). The resulting fit parameters were J = -1.34 cm^-1 and g = 2.10 (1), J = -1.42 cm^-1, g_Cu = 2.10, and Δ = -26.3 cm^-1 (2), and J = -1.70 cm^-1, g_Cu = 2.05, and Δ = -38.1 cm^-1 (3). The reported fitting procedure, implemented in the PHI program, is here used for the first time. Even if this method is only valid in high-symmetry Ln environments, when it is properly used allows a very simple and efficient method to obtain the exchange parameters. In light of the negative anisotropy, compounds 2 and 3 were found to exhibit frequency-dependent tails of out-of-phase signals in the presence of a small external dc field, characteristic of the slow magnetization relaxation of a single-molecule magnet. By using the Kramers-Kronig equations, the effective energy barriers ( U_eff) were derived and reported as U_eff = 10.1 and 5.4 cm^-1 for 2 and 3, respectively.

Filling the gap between the quantum and classical worlds of nanoscale magnetism: giant molecular aggregates based on paramagnetic 3d metal ions

In this review, aspects of the syntheses, structures and magnetic properties of giant 3d and 3d/4f paramagnetic metal clusters in moderate oxidation states are discussed. The term "giant clusters" is used herein to denote metal clusters with nuclearity of 30 or greater. Many synthetic strategies towards such species have been developed and are discussed in this paper. Attempts are made to categorize some of the most successful methods to giant clusters, but it will be pointed out that the characteristics of the crystal structures of such compounds including nuclearity, shape, architecture, etc. are unpredictable depending on the specific structural features of the included organic ligands, reaction conditions and other factors. The majority of the described compounds in this review are of special interest not only for their fascinating nanosized structures but also because they sometimes display interesting magnetic phenomena, such as ferromagnetic exchange interactions, large ground state spin values, single-molecule magnetism behaviour or impressively large magnetocaloric effects. In addition, they often possess the properties of both the quantum and the classical world, and thus their systematic study offers the potential for the discovery of new physical phenomena, as well as a better understanding of the existing ones. The research field of giant clusters is under continuous evolution and their intriguing structural characteristics and magnetism properties that attract the interest of synthetic Inorganic Chemists promise a brilliant future for this class of compounds.

A triacontanuclear [Zn12Dy18] cluster: a ring of [Dy4] cubes

The reaction between Dy(NO3)3·6H2O, Zn(OAc)2·4H2O, salicylaldehyde and 2-amino-isobutyric acid, in MeOH in the presence of NEt3 under solvothermal conditions, led to the isolation of the triacontanuclear mixed-metal cluster [Zn(II)12Dy(III)18(OH)30(L)12(sal)6(OAc)6(NO3)3(H2O)6](NO3)3·12MeOH·5H2O (1·12MeOH·5H2O), which displays frequency- and temperature-dependent out-of-phase magnetic susceptibility signals.

Lanthanide metal–organic frameworks based on the 4,4′-oxybisbenzoic acid ligand: synthesis, structures and physical properties

Using solvothermal synthesis, eight new 3D microporous lanthanide-ions-based MOFs constructed from 4,4′-oxybisbenzoic acid were obtained and displayed two types of architecture.

Syntheses, structures, and properties of a series of novel high-nuclear 3d–4f clusters with mixed amino acids as ligands: {Ln6Cu24}(Ln = Gd, Tb, Pr and Sm)

The first examples of high-nuclear 3d–4f heterometallic clusters {Ln₆Cu₂₄}(Ln = Gd, Tb, Pr and Sm) with mixed amino acid ligands are reported.

Syntheses, structures, photoluminescence and photocatalysis of chiral 3D Cd(ii) frameworks from achiral mixed flexible ligands by spontaneous resolution

Two three-interpenetrating chiral cadmium MOF enantiomers with good photocatalytic activities for degradation of dyes were constructed from achiral flexible ligands.

Two nanosized 3d–4f clusters featuring four Ln6 octahedra encapsulating a Zn4 tetrahedron

Two high-nuclearity 3d–4f clusters Ln₂₄Zn₄ (Ln = Gd and Sm) featuring four Ln₆ octahedra encapsulating a Zn₄ tetrahedron were obtained through the self-assembly of Zn(OAc)₂ and Ln(ClO₄)₃.

Myo-inositol supported heterometallic Dy24M2 (M = Ni, Mn) cages

Two heterometallic cage-like Dy₂₄M₂ (M = Ni, Mn) cluster compounds have been synthesized through self-assembly of the metal ions and the myo-inositol ligand templated by three ClO₄⁻ anions.

Ln–Cd heterometal organic–inorganic hybrid materials based on diverse Ln–Cd oxo-cluster chains: syntheses, structures and visible luminescence

Two types of luminescent Ln–Cd heterometal complexes, I and II, based on diverse Ln–Cd oxo-clusters have been synthesized and characterized.