Family of MnIII4LnIII2 (LnIII= SmIII, GdIII, DyIII) coordination clusters: Experimental and theoretical investigations

Ag(II) as Spin Super-Polarizer in Molecular Spin Clusters

Using quantum mechanical calculations, we examine magnetic (super)exchange interactions in hypothetical, chemically reasonable molecular coordination clusters containing fluoride-bridged late transition metals or selected lanthanides, as well as Ag(II). By referencing to analogous species comprising closed-shell Cd(II), we provide theoretical evidence that the presence of Ag(II) may modify the magnetic properties of such systems (including metal-metal superexchange) to a surprising degree, specifically both coupling sign and strength may markedly change. Remarkably, this happens in spite of the fact that the fluoride ligand is the least susceptible to spin polarization among all monoatomic ligands known in chemistry. In an extreme case of an oxo-bridged Ni(II)₂ complex, the presence of Ag(II) leads to a nearly 17-fold increase of magnetic superexchange and switching from antiferro (AFM)- to ferromagnetic (FM) coupling. Ag(II)─with one hole in its d shell that may be shared with or transferred to ligands─effectively acts as spin super-polarizer, and this feature could be exploited in spintronics and diverse molecular devices.

Slow Magnetic Relaxation in a Co2 Dy Trimer and a Co2 Dy2 Tetramer

The combination of Co(III) and Dy(III) with a compartmental Schiff base ligand (H₃ L=3-[(2-Hydroxy-3-methoxy-benzylidene)-amino]-propane-1,2-diol), presenting three different coordinating pockets, has allowed the synthesis of two novel Co(III)-Dy(III) complexes: [Co₂ Dy(HL)₄ ]NO₃  ⋅ 2CH₃ CN (1), a rare example of trinuclear linear Co^III ₂ Dy^III complex (and the first with slow relaxation of magnetization in absence of a DC field) and [Co₂ Dy₂ (μ₃ -OH)₂ (HL)₂ (OAc)₆ ] ⋅ 4.6H₂ O (2), the first tetranuclear Co^III ₂ Dy^III ₂ cluster with a rhomb-like structure where the Co(III) ions are connected along the short diagonal of the rhomb. 1 presents two different relaxation processes: a fast relaxation dominated by Quantum tunnelling (QT) and a slow relaxation with an energy barrier of 40 K. 2 shows two close relaxation processes without applied DC fields that follow QT and Orbach mechanisms whereas for H_DC =500 Oe, the QT is cancelled and a direct term appears. Here we present the synthesis, X-ray structure and magnetic characterization of these two Co(III)-Dy(III) single-ion/molecule magnets.

Enhancement of the coordinating flexibility in a Schiff–Mannich combo ligand: forced generation of a new NiII–Ophenoxo–LnIII–Oalkoxo–LnIII array (Ln = Gd, Tb, Dy and Ho)

A series of 3d–4f complexes, containing rare NiLn₂O₄ topology, were synthesized by designing a new type of combo Schiff base–Mannich ligand.

Co-existence of ferro- and antiferromagnetic interactions in a hexanuclear mixed-valence CoMnMn cluster sustained by a multidentate Schiff base ligand

The successful utilization of the "direct synthesis" approach yielded the unprecedented hexanuclear complex of formula [Co₂MnMn(L¹)₄Cl₂(μ₃-O)₂(dmf)₄]·2dmf (1) (H₃L is the Schiff base derived from the condensation of salicylaldehyde and 3-aminopropane-1,2-diol). Single crystal X-ray analysis revealed that 1 crystallizes in the monoclinic system P2₁/c and it contains a rare mixed-valence {CoMnMn(μ₂-O)₈(μ₃-O)₂} core where all metal ions are linked through the phenolato and alkoxo groups of the L^3- ligand. Besides the charge balance resulting from the X-ray structure, the oxidation state of the metal ions has been confirmed by XPS spectroscopy. Cryomagnetic studies indicate the coexistence of ferro- (Mn^IV-Mn^II, J₂ = +1.10(3) cm^-1, J₃ = +2.19(3) cm^-1; Mn^II-Mn^II, j = +0.283(3) cm^-1) and antiferromagnetic interactions (Mn^IV-Mn^IV, J₁ = -17.31(4) cm^-1), with the six-coordinate Co^III ions being diamagnetic. DFT type calculations were carried out to substantiate these values. The energy diagram for the different spin states using the best-fit parameters shows the occurrence of six low-lying spin states (S = 0-5) which are close in energy but clearly separated from the remaining ones, with the ground spin state being S = 5. Complex 1 is found to be the first example where weak ferromagnetic exchange between Mn^II ions through the long -O-Mn^IV-O- pathway takes place.

Structure and magnetism of two chair-shaped hexanuclear dysprosium(iii) complexes exhibiting slow magnetic relaxation

Two novel hexanuclear Dy^III complexes with polyhydroxy Schiff-base ligands, [Dy₆(L¹)₄(μ₃-OH)₄(MeOH)₄]Cl₂·2MeOH·2MeCN (1) and [Dy₆(HL²)₂(μ₃-OH)₂(μ₃-OCH₃)₂(piv)₁₀(MeOH)₂] (2) (H₃L¹ = N,N′-bis(3-methoxysalicylidene)(propylene-2-ol)-1,3-diamine, H₃L² = 2,3-dihydroxypropylimino)methyl)-6-methoxyphenol, piv = pivalate), have been prepared under solvothermal conditions and structurally characterized by single-crystal X-ray diffraction, elemental analyses, thermal analyses, and IR spectroscopy. Each of the hexanuclear complexes is constructed with Dy₃ triangular motifs as building blocks, and the six Dy^III ions are arranged in a chair-shaped conformation. Variable-temperature magnetic susceptibility measurements in the temperature range of 2–300 K indicate dominant ferromagnetic exchange interactions between the Dy^III ions in the complexes. Both complexes exhibit slow magnetic relaxation behavior.

We report two novel chair-shaped hexanuclear Dy^III complexes with different polyhydroxy Schiff-base ligands. Both complexes are constructed with Dy₃ triangular motifs as building blocks and exhibit slow magnetic relaxation behavior at low temperature.

Synthesis and magneto-structural studies on a new family of carbonato bridged 3d–4f complexes featuring a [CoII3LnIII3(CO3)] (Ln = La, Gd, Tb, Dy and Ho) core: slow magnetic relaxation displayed by the cobalt(ii)–dysprosium(iii) analogue

A new series of carbonato-bridged complexes containing a CoII3LnIII3 core have been synthesized.