Heterometallic [Cu2Ln3] (Ln = DyIII, GdIIIand HoIII) and [Cu4Ln2] (Ln = DyIIIand HoIII) Compounds: Synthesis, Structure, and Magnetism

Effect of diamagnetic Zn(II) ions on the SMM properties of a series of trinuclear ZnDy2 and tetranuclear Zn2Dy2 (LnIII = Dy, Tb, Gd) complexes: combined experimental and theoretical studies

To study the effect of diamagnetic ions on magnetic interactions, utilizing a compartmental ligand (Z)-2-(hydroxymethyl)-4-methyl-6-((quinolin-8-ylimino)methyl)phenol (LH2), two different series of ZnII-LnIII complexes, namely the trinuclear series of [DyZn2(L)2(μ2-OAc)2(CH3OH)2]·NO3·MeOH (1), [TbZn2(L)2(μ2-OAc)2(CH3OH)2]·NO3·5MeOH·H2O (2), and [GdZn2(L)2(μ2-OAc)2(CH3OH)2]·NO3·MeOH·CHCl3 (3) and the tetranuclear series of [Dy2Zn2(LH)4(NO3)4(μ2OAc)]·NO3·MeOH·H2O (4), [Tb2Zn2(LH)4(NO3)4(μ2-OAc)]·NO3·MeOH·2H2O (5), and [Gd2Zn2(LH)4(NO3)4(μ2-OAc)]·NO3·MeOH·2H2O (6), were synthesized. Trinuclear ZnII-LnIII complexes 1-3 consist of one LnIII ion sandwiched between two peripheral ZnII ions forming a bent type ZnII-DyIII-ZnII array with an angle of 110.64°. Tetranuclear ZnII-LnIII complexes 4-6 are basically a combination of two dinuclear moieties of [LnZn(LH)2(NO3)2]+ connected by one bidentate bridging acetate ion in μ2-OAc coordination mode. The detailed magnetic analysis reveals that complexes 1 and 4 are single molecule magnets having energy barriers of 34.98 K and 46.71 K with relaxation times (τ0) of 5.05 × 10-4 s and 5.24 × 10-4 s, respectively. Ab initio calculations were employed to analyze the magnetic anisotropy and magnetic exchange interaction between the ZnII and LnIII centers with the aim of gaining better insights into the magnetic dynamics of complexes 1-6.

3d–4f Metallacrown complexes with a new sandwich core: synthesis, structures and single molecule magnet behavior

Two heterometallic metallacrown complexes, [Er{Cu₄(butyrat)₄}₂]·Cl₃·MeOH·26H₂O (1) and [Yb{Cu₄(butyrat)₄}₂]·Cl₃·MeOH·26H₂O (2) (H₂butyrat = 3-aminobutyric hydroxamic acid), have been reported.

Synthesis, crystal structures and magnetic properties of a series of pentanuclear heterometallic [CuII3LnIII2] (Ln = Ho, Dy, and Gd) complexes containing mixed organic ligands

Three novel heterometallic compounds [CuII3LnIII2] [Ln = Ho (1), Dy (2) and Gd (3)] containing mixed organic ligands were obtained. 1 and 2 show slow magnetic relaxation behaviour.

Filling Tricompartmental Ligands with GdIII and ZnII Ions: Some Structural and MRI Studies

Here we report the synthesis and characterization of a mononuclear gadolinium complex (Gd) and two heteronuclear Zn-Gd complexes (ZnGd and Zn2Gd), which contain two similar three-armed ligands that display an external compartment suitable for lanthanoid ions, and two internal compartments adequate for zinc (II) ions [H3L′ = (2-(3-formyl-2-hydroxy-5-methyl phenyl)-1,3-bis[4 -(3-formyl-2-hydroxy-5-methylphenyl)-3-azabut-3-enyl]-1,3-imidazolidine; H3L = 2-(5-bromo-2-hydroxy-3-methoxyphenyl)-1,3-bis[4-(5-bromo-2-hydroxy-3-methoxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine]. The synthetic methods used were varied, but the use of a metalloligand, [Zn2(L)AcO], as starting material was the key factor to obtain the heterotrinuclear complex Zn2Gd. The structure of the precursor dinuclear zinc complex is mostly preserved in this complex, since it is based on a compact [Zn2Ln(L)(OH)(H2O)]3+ residue, with a µ3-OH bridge between the three metal centers, which are almost forming an isosceles triangle. The asymmetric spatial arrangement of other ancillary ligands leads to chirality, what contrasts with the totally symmetric mononuclear gadolinium complex Gd. These features were confirmed by the crystal structures of both complexes. Despite the presence of the bulky compartmental Schiff base ligand, the chiral heterotrinuclear complex forms an intricate network which is predominately expanded in two dimensions, through varied H-bonds that connect not only the ancillary ligands, but also the nitrate counterions and some solvated molecules. In addition, some preliminary magnetic resonance imaging (MRI) studies have been made to determine the relaxivities of the three gadolinium complexes, with apparently improved T1 and T2 relaxivities with increasing zinc nuclearity, since both transversal and longitudinal relaxivities appear to enhance in the sequence Gd < ZnGd < Zn2Gd.

Heterometallic Cu/Ln cluster chemistry: ferromagnetically-coupled {Cu4Ln2} complexes exhibiting single-molecule magnetism and magnetocaloric properties

A new family of ferromagnetically-coupled {Cu₄Ln₂} complexes is reported. The compounds exhibit SMM and magnetocaloric properties.

Heterometallic Heptanuclear [Cu5Ln2] (Ln = Tb, Dy, and Ho) Single-Molecule Magnets Organized in One-Dimensional Coordination Polymeric Network

The reaction of a multisite coordination ligand, LH₃, with Cu(II) salts and Ln(NO₃)₃·nH₂O in a 1:2:1 stoichiometric ratio in the presence of triethylamine was found to afford a series of one-dimensional heterometallic [{Cu₅Ln₂(L)₂(μ₃-OH)₄(ClO₄)(NO₃)₃(OH₂)₅}(ClO₄)₂(H₂O)_x]_∞ [Ln = Tb(1), Dy(2) and Ho(3), x = 4.25, 5.5, and 5 for 1-3, respectively] coordination polymers. Complexes 1-3 have been characterized by single crystal X-ray crystallography. The detailed study of the magnetic properties has also been performed and compared with the parent [Cu₅Ln₂] molecular analogues. The ac susceptibility measurements for complexes 1-3 confirm their SMM behavior with the following characteristics: Δ_eff/k_B = 23.4 K, τ₀ = 1.1 × 10^-6 s and Δ_eff/k_B = 27.9 K, τ₀ = 6.6 × 10^-7 s under 0 and 1200 Oe dc fields, respectively for 1; Δ_eff/k_B = 8.3 K, τ₀ = 3.1 × 10^-6 s for 2 under 0 dc field. For 3, the fast QTM below 4 K prevents the estimation of the SMM energy barrier. Remarkably, the magnetic and SMM properties of the previously reported molecular [Cu₅Ln₂] analogues are preserved after their assembly in these coordination networks.

Unprecedented family of heterometallic LnIII[18-metallacrown-6] complexes: syntheses, structures, and magnetic properties

Herein, a new family of Ln^III[18-metallacrown-6] compounds with the formula [Fe₆O₂Ln(tBu-sao)₆(OH)(MeO)₄(MeOH)(H₂O)]·6MeOH [Ln = Dy^III (1), Tb^III (2), Gd^III (3), and Y^III (4), tBu-saoH₂ = 3,5-di-tert-butylsalicylaldoxime] was synthesized through one-pot reactions using tBu-saoH₂, Fe(ClO₄)₃·6H₂O, and Ln(NO₃)₃·6H₂O. The four compounds are isostructural, and the encapsulation of a Ln ion in the ring cavity of 18-metallacrown-6 (18-MC-6) was exhibited for the first time. The structural analysis shows a ship-like 18-MC-6 core with a beset lanthanide ion connecting six ring oxygen atoms (O_MC). Magnetic measurements reveal domain antiferromagnetic coupling interactions between metal ions and field-dependent slow magnetic relaxation in 1-3.