Tetranuclear Lanthanide Clusters Research Articles

Synthesis of two lanthanide clusters LnIII4 (Gd4 and Dy4) with [2 × 2] square grid shape: Magnetocaloric effect and slow magnetic relaxation behaviors

Two isostructural tetranuclear lanthanide clusters named [Ln4(L)4(CH3O)4]·CH3OH (Ln = Gd(III) for 1, Dy(III) for 2, H2L = N′-(2-hydroxy-3-methoxybenzylidene)-6-(hydroxymethyl) picolinohydrazide) were successfully isolated by using a polydentate Schiff based ligand and Ln(III) nitrate salts. The structures of 1 and 2 were characterized by X-ray structural analyses, they are held by four double deprotonated ligands L2−. In them all the lanthanide ions are eight-coordinated and distributed over four vertices of a parallelogram, presenting a Ln4 cluster with a strict [2 × 2] square grid pattern. The details of magnetic analysis show that 1 displays weak anti-ferromagnetic exchange between neighboring Gd(III) ions through carboxylate oxygen and methanol oxygen ligand atoms. Furthermore, 1 exhibits significant magnetocaloric effect with the maximum entropy change –ΔSm value of 28.5 J/(kg·K) for ΔH = 7.0 T at 2.0 K. For compound 2, remarkable slow magnetic relaxation behaviors are observed in the presence of zero magnetic field with τ0 = 1.02 × 10−6 s and energy barrier ΔE/kB = 43.24 K.

A series of Ln4III clusters: Dy4 single molecule magnet and Tb4 multi-responsive luminescent sensor for Fe3+, CrO42−/Cr2O72− and 4-nitroaniline

Five tetranuclear lanthanide clusters of compositions [Ln4L4(NO3)2(Piv)2]·2CH3OH (Ln = Gd (1), Tb (2), Dy (3), Ho (4), Er (5); H2L = 2-(((2-hydroxy-3-methoxybenzyl)imino)methyl)-6-methoxyphenol; Piv = pivalic acid) were synthesized under solvothermal conditions. The structures of 1–5 were characterized by single-crystal X-ray crystallography. Complexes 1–5 possess a zig-zag topology with [Ln4O6] cores being formed by the fusion of oxygen atom-bridged two [Ln2O2] moieties. Direct-current magnetic susceptibility studied in the 2–300 K range revealed weak antiferromagnetic interactions in 1, 2, 4, 5 and ferromagnetic interactions in 3. Complex 3 exhibits single molecule magnet (SMM) behavior. The luminescence studies indicated that complex 2 can serve as highly sensitive and selective luminescent materials for Fe3+, CrO42−, Cr2O72− and 4-nitroaniline (4-NA), demonstrating that complex 2 should be a potential candidate for multi-responsive luminescent sensor.

Self-assembly of tetra-nuclear lanthanide clusters via atmospheric CO2 fixation: interesting solvent-induced structures and magnetic relaxation conversions

Two systems of carbonate complexes are constructed via chemical fixation of atmospheric CO2, in which solvent-induced different structures and magnetic behaviors are observed.

Enhancement of Magnetocaloric Effect through Fixation of Carbon Dioxide: Molecular Assembly from Ln4 to Ln4 Cluster Pairs

A series 1.Ln of tetranuclear lanthanide clusters [Ln4(μ4-O)L2(PhCOO)6]·solvent (Ln = Gd (1.Gd), Dy (1.Dy), Ho (1.Ho)) and octanuclear lanthanide Ln4 cluster pairs 2.Ln [Ln8(μ3-OH)4(CO3)2L4(PhCOO)8]·solvent (Ln = Gd (2.Gd), Dy (2.Dy), Tb (2.Tb)) were assembled by using a bi-Schiff-based ligand H2L and characterized structurally and magnetically. Interestingly, the octanuclear Ln4 cluster pairs 2.Ln are proposed to be assembled from the tetranuclear clusters 1.Ln through the uptake of CO2 from air in a more basic media. X-ray structural analyses approved the possible evolution mechanism. Magnetic studies reveal the coexistence of ferro- and anti-ferromagnetic interaction in 1.Gd and 2.Gd by simulating the direct-current magnetic susceptibility and indicate the CO32- bridges produce weak ferromagnetic interaction in 2.Gd rather than anti-ferromagnetic interaction by benzoate bridges in 1.Gd. The magnitude of the magnetocaloric effect has been examined and shows that complex 2.Gd exhibits larger magnetocaloric effect than 1.Gd, which could be probably ascribed to the weak ferromagnetic interaction produced by the CO32- bridges.

Three pillared-layer 3d–4f heterometallic frameworks based on tetranuclear lanthanide clusters

Three 3D heterometallic 3d–4f MOFs, formulated as [Gd4L12(Cu10I8)(H2O)10]·2ClO4·4H2O (1), [La4(Ox)2L8(Cu7I5)(H2O)4]·2ClO4·4H2O (2), and [La4Na(Ox)3L8(Cu7I6)(H2O)3]·5H2O (3) [where Ox = oxalate, HL = 4-pyridin-4-ylbenzonic acid], have been made under hydrothermal conditions. All the MOFs are characterized by elemental analysis, IR, thermogravimetric analysis, powder X-ray diffraction, and single-crystal X-ray diffraction. These novel 3D pillared-layer frameworks are constructed from 2D lanthanide–organic layers based on tetranuclear lanthanide clusters, and pillared by diverse copper(I) halide motifs. The oxalate is introduced as a coligand to make the hook-like tetramer in compound 1 into compact butterfly-like tetramer in compounds 2 and 3 due to its size preference.

Series of dinuclear and tetranuclear lanthanide clusters encapsulated by salen-type and β-diketionate ligands: single-molecule magnet and fluorescence properties

Three dinuclear [Ln2H2OL(1)2(acac)2]·solvent (1, Ln = Gd, solvent = 2CH2Cl2; 2, Ln = Tb, no solvent; 3, Ln = Er, solvent = (C2H5)2O), and two tetranuclear lanthanide clusters [Ln4(μ3-OH)2L(2)2(acac)6]·2(solvent) (4, Ln = Tb, solvent = CH3OH; 5, Ln = Dy, solvent = CH3CN) were characterized in terms of structure, fluorescence and magnetism. The dinuclear lanthanide complexes were constructed by a rigid salen-type ligand H2L(1) = N,N'-bis(salicylidene)-o-phenylenediamine and β-diketonate (acac = acetylacetonate) ligands, while the tetranuclear clusters were formed from the flexible ligand H2L(2) = N,N'-bis(salicylidene)-1,2-ethanediamine. Crystal structure analysis indicates that the rigid ligand favors the double-decker sandwich structure (Ln2L(1)2), in which the two lanthanide ions have different coordination numbers and geometry, while the more flexible ligand (H2L(2)) leads to planar tetranuclear clusters. The relationship between their respective magnetic anisotropy and ligand-field geometries and their fluorescence properties was investigated. The Dy and Tb-containing clusters exhibit typical visible fluorescence properties, and single-molecule magnet behavior is seen in complex 5.

A series of di-, tri- and tetranuclear lanthanide clusters with slow magnetic relaxation for Dy2 and Dy4

A series of dinuclear, trinuclear and tetranuclear lanthanide complexes, formulated as [Nd2(Acc)6(H2O)4]3 [Nd2(Acc)6(H2O)6]·Cl24·8H2O (1), [Dy2(Acc)4(H2O)8]·Cl6·5.89H2O (2), [Ln3(Acc)10(H2O)6]·(ClO4)9·4H2O (Ln = La, (3); Nd, (4)) and [Ln4(μ3-OH)4(Acc)6(H2O)7(ClO4)] ·(ClO4)7·11H2O (Ln = Dy, (5); Yb, (6)), have been synthesized through the reaction of 1-amino cyclohexanel-carboxylic acid (Acc) and LnCl3/Ln(ClO4)3. Crystal structure analysis reveals that complexes 1 and 2 show dinuclear lanthanide cluster, complexes 3 and 4 have three lanthanide ions with a linear arrangement, while complexes 5 and 6 exhibit a cubane-like [Ln4(μ3-OH)4]8+ (Ln = Dy and Yb) cluster core. Their structural variations are attributed to the effect of anions and lanthanide contraction. Magnetic studies indicate that the Dy2 and Dy4 clusters exhibit slow relaxation of magnetization.

Planar tetranuclear lanthanide clusters with the Dy4 analogue displaying slow magnetic relaxation

Two isostructural tetranuclear lanthanide clusters of general formula [Ln(III)(4)(μ(3)-OH)(2)(o-van)(4)(O(2)CC(CH(3))(3))(4)(NO(3))(2)]·CH(2)Cl(2)·1.5H(2)O (Ln = Gd (1) and Dy (2)) (o-van = 3-methoxysalicylaldehydato anion) are reported. The metallic cores of both complexes display a planar 'butterfly' arrangement. Magnetic studies show that both are weakly coupled, with 2 displaying probable SMM behaviour.

Synthesis and Structural Characterization of Tetra‐ and Pentanuclear Lanthanide Hydroxido Clusters

AbstractTetra‐ and pentanuclear lanthanide clusters having dibenzoylmethanido and o‐nitrophenolato as ligands in the coordination sphere were prepared. Treating [LnCl3·6H2O] (Ln = Er, Tm) with dibenzoylmethane and o‐nitrophenol in the presence of triethylamine yielded the pentanuclear lanthanide clusters HNEt3+[Ln5(μ3‐OH)4(μ4‐OH)(Ph2acac)7(o‐O2NC6H4O)3Cl]– (Ln = Er, Tm). Under the same reaction conditions but using Yb and Lu as center metals, tetranuclear lanthanide clusters [Ln4(μ3‐OH)2(Ph2acac)8(o‐O2NC6H4O)2] (Ln = Yb, Lu) were obtained. The structures of all new compounds were confirmed by single‐crystal X‐ray diffraction. The anions of the pentanuclear lanthanide cores are square pyramidal. Each triangular face of the square pyramid is capped by one μ3‐O moiety. In the square base, four lanthanide atoms are linked by one μ4‐O atom. The formation of the hydroxido bridges can be explained by deprotonation of the coordinated water molecules.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Synthesis and Structural Characterization of a Series of Tetranuclear Lanthanide Clusters

AbstractTetranuclear lanthanide clusters of composition [Ln4(μ3‐OH)2(Ph2acac)10] (Ln = Pr, Nd, and Sm) (Ph2acac = dibenzoylmethanide) were prepared starting from [LnCl3·(n H2O)] (n = 6, 7) with 2.5 equivalents dibenzoylmethane in presence of triethylamine. Single crystals X‐ray analyses of compounds 1 ‐ 3 revealed that each cluster consists of four lanthanide atoms, two μ3‐oxygen atoms, and ten Ph2acac ligands, which make up the peripheral part of the cluster. Three types of coordination modes (η2‐, (μ‐O)‐η2‐, and μ‐O)2‐η2) are observed for the Ph2acac ligation to the metal centers.

Synthesis, crystal structure and magnetic properties of μ4-oxo-centered tetranuclear lanthanide clusters

μ4-Oxo-centered tetranuclear lanthanide (Gd, Tb) clusters with the 1,3-bis(2-hydroxy-3-methoxybenzylamino)propan-2-ol (H3L) ligand have been synthesized and their crystal structure and magnetic properties are presented.