Dinuclear Lanthanide Research Articles

Highly sensitive sensing device based on highly luminescent lanthanide nanocluster for biomarker in human urine and serum

The level of L-kynurenine (L-kyn) can reflect the health state of human body, and the determination of L-kyn can be used for the medical diagnosis of several cancers and neurological diseases. In this work, a series of air-, water-, and thermo-stable dinuclear lanthanide nanoclusters [Ln2(2,5-DFBA)6(phen)2] (Tb 1, Eu 2, Gd 3, 2,5-DFBA = 2,5-difluorobenzoic acid, phen = 1,10-phenanthroline) are obtained by a facial method. 1 and 2 show very high luminescence quantum yields (QYs) of 71.7% and 81.8%, respectively. Interestingly, investigation reveals that 1 is a quick, highly sensitive and selective sensor for L-kyn in real samples of urine and serum. Furthermore, transmission electron microscope (TEM) results reveal that nanocluster 1 is stable in solution and can be uniform distributed on the base, suggesting it can be deposited on various supports to fabricate sensing devices. Thus, 1 is fabricated into a sensitive test paper for the eye-readable detection of L-kyn in real samples of human urine and serum. The limit of detection (LOD) as low as 0.3 μM, which is enough to rapidly determine L-kyn in human body liquor (usually 5 μM in healthy human body).

Synthesis of Two New Dinuclear Lanthanide Clusters and Visual Bifunctional Sensing Devices Based on the Eu Cluster

AbstractThe development of visual and multifunctional sensors, and further the fabrication of portable sensing devices is of great importance. Herein, two dinuclear lanthanide clusters are designed, and their accurate molecules are determined to be [Ln2(DFBA)6(dmp)2(H2O)2] (Ln3+ = Eu3+ (1‐Eu) or Tb3+ (1‐Tb), HDFBA = 3,4‐difluorobenzoic acid, dmp = 4,7‐dimethyl‐1,10‐phenanthroline), by single‐crystal X‐ray diffraction. Interestingly, 1‐Eu shows rapid detection of ferrous ions (Fe2+) and acetylacetone (acac), with the limit of detection (LOD) as low as 5.6 and 1.0 ppb, respectively. LOD of 5.6 ppb for Fe2+ is far lower than the standard of World Health Organization (0.3 ppm, SDWA) and Chinese rural water quality standards (0.5 ppm, GB25467‐2010) for drinking water. As far as it is known, 1‐Eu is the most sensitive chemosensor for the detection of acac; the sensing can be discriminated by the naked eyes under 365 nm UV light. Furthermore, portable sensing devices of agarose gel, test paper, and sprayed films on plastic tube, glass, coin, test paper, stone, leaf, carbon rod, and iron sheet surfaces, based on 1‐Eu solution, are fabricated by facile methods, with visual and quick detection of Fe2+ in water under various conditions, and show excellent recyclable sensing performance for acac vapor.

Synthesis and Spectral Studies of Some Homo Dinuclear Lanthanide(III) Complexes of a Mesogenic Schiff Base.

A mesogenic Schiff base, N,N'-di(4-decyloxysalicylidene)-1',8'-diamino-3',6'-dioxaoctane (H2L) and a series of homo dinuclear lanthanide(III) complexes of the type [Ln2(LH2)3(NO3)4](NO3)2, (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, and Ho) were synthesized and characterized by elemental analysis, mass spectrometry, FTIR, and NMR spectral techniques. The IR and NMR spectral evidences imply bonding of a neutral bidentate H2L species through two phenolate oxygen atoms in its zwitterionic form to LnIII, rendering the overall geometry of the complexes as a seven-coordinate polyhedron - possibly distorted mono-capped octahedron. Differential scanning calorimetry (DSC) and polarizing optical microscopic (POM) studies reveal mesogenic properties (smectic-X, smectic-A and nematic mesophases) in the ligand over a wide range of temperature but none mesomorphism in the LnIII complexes synthesized under this study. Luminescence studies exhibit emissions of H2L and TbIII complex.

Magneto-thermal and magnetization relaxation dynamics of a family of di-nuclear lanthanide complexes

The reaction of Ln(NO3)3·nH2O (where Ln = Gd, Tb, Dy or Yb) in the presence of sodium acetate led us to isolate a family of structurally analogous dinuclear lanthanide complexes with the general molecular formula of [Ln2(CH3COO)4(NO3)2(H2O)4]. 2H2O (where Ln = Gd (1) or Tb (2) or Dy (3) or Yb (4)), which are characterized by single-crystal X-ray diffraction. The dc magnetic susceptibility measurements were performed on 1 reveal the presence of a weak ferromagnetic exchange between the Gd(III) center (J = +0.01 cm−1; −2JS1.S2 Hamiltonian). This weak exchange interaction in 1 is presumably overcome by the external magnetic field, and therefore, the X-band EPR spectral features of 1 were simulated by considering the single-ion spin Hamiltonian parameter (g = 1.98, D = 0.03 cm−1, and ∣E/D∣= 0.004). In contrast to 1, complexes 2–4 exhibit a weak antiferromagnetic exchange between the Ln(III) centers. The magnetization relaxation dynamics studies performed on the anisotropic complexes (2–4) show slow relaxation of magnetization in the presence of an optimum external magnetic field. The spin–lattice relaxation predominantly follows the Direct and Raman mechanism exclusively, and the Orbach process was found to be non-existent. By employing ab initio calculations, the electronic structure and the mechanism of magnetization relaxation dynamics of 2–4 have been investigated. The magnetocaloric effect parameter for 1 shows a change in magnetic entropy (−ΔSm) value of 39 J Kg−1 K−1 at 2.0 K (ΔH = 70 kOe), which is one of the largest −ΔSm value registered among the various discrete molecular coolants reported in the literature..

Precise measurement of angles between two magnetic moments and their configurational stability in single-molecule magnets

A key parameter for the low-temperature magnetic coupling of in dinuclear lanthanide single-molecule magnets (SMMs) is the barrier $U_{FA}$ resulting from the exchange and dipole interactions between the two $4f$ moments. Here we extend the pseudospin model previously used to describe the ground state of dinuclear endofullerenes to account for variations in the orientation of the single-ion anisotropy axes and apply it to the two SMMs Dy$_2$ScN@C$_{80}$ and Dy$_2$TiC@C$_{80}$. While x-ray magnetic circular dichroism (XMCD) indicates the same $J_z=15/2$ Dy groundstate in both molecules, the Dy-Dy coupling strength and the stability of magnetization is distinct. We demonstrate that both the magnitude of the barrier $U_{FA}$ and the angle between the two $4f$ moments are determined directly from precise temperature-dependent magnetization data to an accuracy better than $1^{\circ}$. The experimentally found angles between the $4f$ moments are in excellent agreement with calculated angles between the quantisation axes of the two Dy ions. Theory indicates a larger deviation of the orientation of the Dy magnetic moments from the Dy bond axes to the central ion in Dy$_2$TiC@C$_{80}$. This may explain the lower stability of the magnetisation in Dy$_2$TiC@C$_{80}$, although it exhibits a $\sim 49\%$ stronger exchange coupling than in Dy$_2$ScN@C$_{80}$.

Structures, luminescence properties and single-molecule magnet behavior of four dinuclear lanthanide compounds

Four new dinuclear lanthanide(Ⅲ) compounds, namely [Ln2(dbm)4L2(CH3OH)2]·2CH3OH (LnⅢ = Sm(1) and Dy(4), Hdbm = 1,3-diphenylpropane-1,3-dione, H2L = N'-[(1E)-[5-(hydroxymethyl)furan-2-yl]methylidene]pyrazine-2-carbohydrazide), [Eu2(dbm)4L2](2) and [Tb2(dbm)4L2] ·CH3OH (3)), have been synthesized, and structurally and magnetically characterized. The Eu3+ ion is eight coordinated with two bidentate β-diketonate and two μ2-O bridging multidentate ligands. The Dy3+ ion is nine coordinated with two bidentate β-diketonate, one methanol molecule, and two μ2-O bridging multidentate ligands. Magnetic measurements indicated that slow magnetic relaxation behaviors were observed the dilution in cognate Y(Ⅲ) matrix of compound 4, with energy barrier (ΔE/kB) of 47.21 K under dc field of 2000 Oe and τ0 of 1.21 × 10−10 s. Additionally, solid-state luminescence properties reveal that 2-4 display the characteristic LnⅢ luminescence at room temperature.

Slow Magnetic Relaxation in Mono- and Bimetallic Lanthanide Tetraimido-Sulfate S(NtBu)4 2- Complexes.

Lanthanide ions are particularly well‐suited for the design of single‐molecule magnets owing to their large unquenched orbital angular momentum and strong spin‐orbit coupling that gives rise to high magnetic anisotropy. Such nanoscopic bar magnets can potentially revolutionize high‐density information storage and processing technologies, if blocking temperatures can be increased substantially. Exploring non‐classical ligand scaffolds with the aim to boost the barriers to spin‐relaxation are prerequisite. Here, the synthesis, crystallographic and magnetic characterization of a series of each isomorphous mono‐ and dinuclear lanthanide (Ln=Gd, Tb, Dy, Ho, Er) complexes comprising tetraimido sulfate ligands are presented. The dinuclear Dy complex [{(thf)2Li(NtBu)2S(tBuN)2DyCl2}2 ⋅ ClLi(thf)2] (1c) shows true signatures of single‐molecule magnet behavior in the absence of a dc field. In addition, the mononuclear Dy and Tb complexes [{(thf)2Li(NtBu)2S(tBuN)2LnCl2(thf)2] (2b,c) show slow magnetic relaxation under applied dc fields.

Near-infrared luminescence and magnetism of dinuclear lanthanide complexes constructed from a schiff-base and different β-diketonate coligands

Seven new dinuclear lanthanide complexes based on a schiff-base ligand H2L and β-diketonate coligands have been synthesized and characterized: [Eu2(acac)4(HL)2]·3C2H5OH (1), [Ln2(acac)2(HL)4]·6C2H5OH (Ln = Tb(2), Dy(3), Er(4), Yb(5)), [Dy2(bfa)4(HL)2]·2H2O (6), [Dy2(tmhd)2(HL)4] (7) (H2L = 5-methylsalicylaldehyde-2-aminobenzoylhydrazone; Hacac = acetylacetone; Hbfa = benzoyltrifluoroacetylacetone; Htmhd = 2,2,6,6-tetramethylheptane-3,5-dione). These complexes are all centrosymmetric and bridged by phenoxo-O, offered with Ln2O2 cores. Meanwhile, the near-infrared luminescence measurements show that the characteristic emission peaks of ErIII (4) and YbIII (5) ions can be observed, which means the effective sensitization of the ligands. Subsequently, the dynamic magnetization properties studies show that 3, 6 and 7 exhibit slow magnetic relaxation behavior, typical SMM behavior, resulting in an effective barrier of 48.42 K (3) and 54.82 K (6) under an applied 800 Oe dc field, and 60.59 K for 7 under 3000 Oe dc field. In particular, this work demonstrates that the magnetic properties can be modulated by regulating the electron effects of terminal substituents on the coligands.

Azide-Coordination in Homometallic Dinuclear Lanthanide(III) Complexes Containing Nonequivalent Lanthanide Metal Ions: Zero-Field SMM Behavior in the Dysprosium Analogue.

A series of homometallic dinuclear lanthanide complexes containing nonequivalent lanthanide metal centers [Ln2(LH2)(LH)(CH3OH)(N3)]·xMeOH·yH2O [1, Ln = DyIII, x = 0, y = 2; 2, Ln = TbIII, x = 1, y = 1] have been synthesized [LH4 = 6-((bis(2-hydroxyethyl)amino)-N'-(2-hydroxybenzylidene)picolinohydrazide] and characterized. The dinuclear assembly contains two different types of nine-coordinated lanthanide centers, because the nonequivalent binding of the azide co-ligand as well as the varying coordination of the deprotonated Schiff base ligand. Detailed magnetic studies have been performed on the complexes 1 and 2. Complex 1 and its diluted analogue (15%) are zero-field SMMs with effective energy barriers (Ueff) of magnetization reversal equal to 59(3) K and 66(3) K and relaxation times of τ0 = 10(4) × 10-6 s and 10(4) × 10-8 s, respectively. On the other hand, complex 2 shows a field-induced SMM behavior. Combined ab initio and density functional theory calculations were performed to explain the experimental findings and to unravel the nature of the magnetic anisotropy, exchange-coupled spectra, and magnetic exchange interactions between the two lanthanide centers.

Synthesis, Characterization, and Catalytic Activity of Dinuclear Rare-Earth Metal Alkyl Complexes Bearing 2,6-Diisopropylphenylamidomethyl Functionalized Pyrrolyl Ligand

Synthesis, Characterization, and Catalytic Activity of Dinuclear Rare-Earth Metal Alkyl Complexes Bearing 2,6-Diisopropylphenylamidomethyl Functionalized Pyrrolyl Ligand

Synthesis, structures, photoluminescence and magnetic properties of three dinuclear lanthanide(III) complexes derived from 4‐fluorophenylselenoacetic acid

AbstractThree novel dinuclear lanthanide(III) complexes [Ln2L6(phen)2] (Ln=EuIII (1), TbIII (2), Dy III (3)), derived from 4‐fluorophenylselenoacetic acid and 1,10‐phenanthroline, have been synthesized and characterized by elemental analysis, IR, TGA, powder X‐ray diffraction and single‐crystal X‐ray diffraction analysis. Single crystal X‐ray diffraction reveal they are isostructural and crystallize in the monoclinic crystal system, space group P2(1)/c. The investigations on luminescent properties of Eu(III) complex 1 and Tb(III) complex 2 exhibit the characteristic emissions of EuIII (5D0→7F0‐4) and TbIII (5D4→7F6‐3), and the corresponding luminescent lifetimes are 1.52 and 1.10 ms, respectively. Temperature‐dependent photoluminescence studies show the emission intensities and lifetimes for both complexes decrease upon increasing temperature, which indicates complexes 1 and 2 have the potential for sensing temperature. The magnetic studies reveal that Dy(III) complex 3 exhibits weak antiferromagnetic interactions and slow magnetic relaxation behavior.

Dinuclear Lanthanide(III) Complexes from the Use of Methyl 2-Pyridyl Ketoxime: Synthetic, Structural, and Physical Studies.

The first use of methyl 2-pyridyl ketoxime (mepaoH) in homometallic lanthanide(III) [Ln(III)] chemistry is described. The 1:2 reactions of Ln(NO3)3·nH2O (Ln = Nd, Eu, Gd, Tb, Dy; n = 5, 6) and mepaoH in MeCN have provided access to complexes [Ln2(O2CMe)4(NO3)2(mepaoH)2] (Ln = Nd, 1; Ln = Eu, 2; Ln = Gd, 3; Ln = Tb, 4; Ln = Dy, 5); the acetato ligands derive from the LnIII—mediated hydrolysis of MeCN. The 1:1 and 1:2 reactions between Dy(O2CMe)3·4H2O and mepaoH in MeOH/MeCN led to the all-acetato complex [Dy2(O2CMe)6(mepaoH)2] (6). Treatment of 6 with one equivalent of HNO3 gave 5. The structures of 1, 5, and 6 were solved by single-crystal X-ray crystallography. Elemental analyses and IR spectroscopy provide strong evidence that 2–4 display similar structural characteristics with 1 and 5. The structures of 1–5 consist of dinuclear molecules in which the two LnIII centers are bridged by two bidentate bridging (η1:η1:μ2) and two chelating-bridging (η1:η2:μ2) acetate groups. The LnIII atoms are each chelated by a N,N’-bidentate mepaoH ligand and a near-symmetrical bidentate nitrato group. The molecular structure of 6 is similar to that of 5, the main difference being the presence of two chelating acetato groups in the former instead of the two chelating nitrato groups in the latter. The geometry of the 9-coordinate LnIII centers in 1, 5 and 6 can be best described as a muffin-type (MFF-9). The 3D lattices of the isomorphous 1 and 5 are built through H-bonding, π⋯π stacking and C-H⋯π interactions, while the 3D architecture of 6 is stabilized by H bonds. The IR spectra of the complexes are discussed in terms of the coordination modes of the organic and inorganic ligands involved. The Eu(III) complex 2 displays a red, metal-ion centered emission in the solid state; the TbIII atom in solid 4 emits light in the same region with the ligand. Magnetic susceptibility studies in the 2.0–300 K range reveal weak antiferromagnetic intramolecular GdIII…GdIII exchange interactions in 3; the J value is −0.09(1) cm−1 based on the spin Hamiltonian Ĥ = −J(ŜGd1·ŜGd2).

Syntheses, crystal structures, thermodynamic and fluorescent properties of dinuclear lanthanide complexes constructed with 2-fluorobenzoic acid and 5,5′-dimethy-2,2′-bipyridine

2-fluorobenzoic acid and 5,5′-dimethy-2,2′-bipyridine were used to construct two novel isostructural lanthanide complexes [Ln(2-FBA)3(5,5′-DM-2,2′-bipy)]2 (Ln = Eu(1), Tb(2); 2-FBA = 2-fluorobenzoate; 5,5′-DM-2,2′-bipy = 5,5′-dimethy-2,2′-bipyridine) by conventional solution method. They were characterized by infrared spectroscopy (IR), elemental analysis and single-crystal X-ray diffraction. The crystal description based on single-crystal X-ray diffraction data revealed that both of the complexes gave the triclinic crystal structure, belonging to the Pī space group. The two complexes were an infinite one-dimensional (1D) chain by hydrogen bonding (C–H…F) interactions to give a 2D supermolecular structure. Additionally, thermal behavior of the complexes was investigated by TG-DSC/FTIR technology in detail. The molar heat capacities of the two complexes in the temperature range of 278.15-423.15 K were determined by a DSC instrument, and their thermodynamic functions (HT-H298.15 K) and (ST-S298.15 K) were calculated. Beyond that, the fluorescence spectra and fluorescence lifetime of the complexes 1 and 2 were also evaluated.

Structures and magnetic properties of two dinuclear lanthanide complexes based on 8-hydroxyquinoline Schiff base derivatives

Based on 8-hydroxyquinoline Schiff base derivative and auxiliary ligand β-diketonate, two new dinuclear lanthanide complexes [Gd2(L1)2(bfac)4] (1) and [Dy2(L2)2(acac)2(CH3OH)2]•CH3OH (2) (HL1 = 2-[((4-phenethyl)-imino)methyl]-8-hydroxyquinoline, H2L2 = 2-[((4-methyl)-2-(arboxyl)-imino)]methyl]-8-hydroxyquinoline, Hbfac = hexafluoroacetylacetonate, Hacac = acetylacetonate,) were successfully isolated and characterized. Structural analysis reveal that complexes 1 and 2 both contain a binuclear Ln2 cluster, in which two eight-coordinated Ln(III) ions are located in distorted dodecahedral geometry and bridged by phenoxide oxygen atom. In addition, their magnetic properties are investigated in detail. The results suggest that ferromagnetic interactions between adjacent Gd3+ ions can be observed in 1, which exhibits remarkable magnetic refrigeration properties with -ΔSmax = 17.74 J kg−1 K−1 (T = 2.0 K and ΔH = 7.0 T). Complex 2 displays slow magnetic relaxation behaviors with ΔE/kB ≈ 2.16 K and τ0 ≈ 1.38 × 10−5 s.

Gadolinium‐Triradical Complex with Ground S = 10 State: Synthesis, Structural Characterization and Magnetic Studies

AbstractTwo novel dinuclear lanthanide(III) complexes were prepared with a triradical 2,4,6‐tris{p‐(N‐oxy‐N‐t‐butylamino)phenyl}‐1,3,5‐triazine (L), yielding [{LnIII(hfac)3(ethanol)(L)}2] (Ln2L2, Ln = Gd and La; hfac = 1,1,1,5,5,5‐hexafluoropentane‐2,4‐dionate). Compound Ln2L2 has a cyclic structure in which two Ln ions are bridged by two triradical ligands. The cyclic dimers form quasi‐two‐dimensional (2D) structures via intermolecular hydrogen bonding and π‐π interactions. The La derivative, in which only L shows magnetic behavior, exhibits intraligand ferromagnetic and interligand antiferromagnetic 2 p–2 p couplings. Compound Gd2L2 shows ferromagnetic 4 f–2 p and intraligand 2 p–2 p couplings with a high‐spin state of S = 10.

Structures and magnetic properties of acyloxy-O bridged Ln2 compounds: Gd2 compound displaying magnetic refrigeration property

In order to study magnetocaloric effect, we synthesized five new dinuclear lanthanide (Ⅲ) compounds, namely [Ln(dbm)2HL(CH3OH)]2•2CH3OH (LnⅢ=Nd(1), Gd(2) and Tm(5), dbm =1,3-diphenylpropane-1,3‑dione, HL = N'-[(1E)-[5-(hydroxymethyl)furan-2-yl]methylidene]pyrazine-2-carbohydrazide) and [Ln(dbm)2HL]2 (LnⅢ = Ho(3) and Er(4)), and characterized by elemental analysis, IR, PXRD, UV–vis and single crystal X-ray diffraction. The structures of compounds 1–5 are very similar with a planar [Ln2O2]. Magnetic studies indicated that weak antiferromagnetic interaction are present between the Gd(Ⅲ) ions within 2. Meanwhile, Gd2 compound displays magnetic refrigeration property with the max entropy change (-ΔSm) of 16.58 J K − 1kg−1 (T = 2.0 K and ΔH = 70 kOe).

A new family of dinuclear lanthanide complexes exhibiting luminescence, magnetic entropy changes and single molecule magnet behaviors

Four isomorphic and dinuclear lanthanide complexes were synthesized. Complexes EuIII and TbIII exhibit strong emissions, while GdIII shows the magnetocaloric effect and DyIII displays a single-molecule magnet.

Helix-mediated over 1 nm-range chirality recognition by ligand-to-ligand interactions of dinuclear helicates.

Long-range chirality recognition between the two chiral guest ligands can be tuned based on the helix distances (dLn–Ln = 11.5 and 14.0 Å) of bis-diketonate bridged dinuclear lanthanide complexes (2Th and 3Th, respectively) used as mediators. Both 2Th and 3Th form one-dimensional (1D) helical structures upon terminal binding of two chiral guest co-ligands (LR or LS). Long-range chiral self-recognition is achieved in self-assembly of 2Th with LR and LS to preferentially form homochiral assemblies, 2Th-LR·LR and 2Th-LS·LS, whereas there is no direct molecular interaction between the two guest ligands at the terminal edges. X-ray crystal structure analysis and density functional theory studies reveal that long-range chiral recognition is achieved by terminal ligand-to-ligand interactions between the bis-diketonate ligands and chiral guest co-ligands. Conversely, in self-assembly of 3Th with a longer helix length, statistical binding of LR and LS occurs, forming heterochiral (3Th-LR·LS) and homochiral (3Th-LR·LR and 3Th-LS·LS) assemblies in an almost 1 : 1 ratio. When phenyl side arms of the chiral guest co-ligands are replaced by isopropyl groups (L′R and L′S), chiral self-recognition is also achieved in the self-assembly process of 3Th with the longer helix length to generate homochiral (3Th-L′R·L′R and 3Th-L′S·L′S) assemblies as the favored products. Thus, subtle modification of the chiral guests is capable of achieving over 1.4 nm-range chirality recognition.

Lanthanide nitrato complexes bridged by the bis-tridentate ligand 2,3,5,6-tetra(2-pyridyl)pyrazine: Syntheses, crystal structures, Hirshfeld surface analyses, luminescence properties, DFT calculations, and magnetic behavior

Six dinuclear lanthanide(III) nitrato complexes [Ln(NO3)3(H2O)]2(μ-tppz) (where tppz = 2,3,5,6-tetra(2-pyridyl) pyrazine and Ln(III) = Nd (1), Sm (2), Eu (3), Gd (4), Tb (5), and Dy (6)) with bis-tridentate N-heterocyclic 2,3,5,6-tetra(2-pyridyl)pyrazine as bridging ligand have been solvothermally synthesized and characterized via elemental analysis, infrared spectroscopy, thermogravimetric analysis, single-crystal X-ray diffraction, and powder X-ray diffraction. The 3-D Hirshfeld surface and 2-D fingerprint plots show that the main interactions in 1–6 are the O⋯H/H⋯O intermolecular interactions with relative contributions of about 62%. Although the poor lanthanide(III)-centered luminescence properties clearly point to the efficiency of nonradiative quenching processes (presence of water molecules in the coordination sphere of the lanthanide(III) ions), the ligand tppz is better suited to sensitize the lanthanide(III)'s emissions of EuIII and NdIII than SmIII, TbIII, and DyIII. Finally, the magnetic data of DyIII comple×6 reveals antiferromagnetic coupling between DyIII ions.

Two lanthanide-based dinuclear clusters (Gd2 and Dy2) with Schiff base derivatives: Synthesis, structures and magnetic properties

Two dinuclear lanthanide compounds, [Gd2(L1)(dbm)5] (1) (HL1 = N′-(2-pyridinylmethylene)-2-(hydroxyimino)propanehydrazide), Hdbm = 1, 3-diphenyl-1,3-propanedione), [Dy2(L2)2(dbm)2(CH3OH)2]·3CH3OH (2) (H2L2 = 2-[[(4-methyl-2-carboxyl)imino]methyl]-8-hydroxyquinoline) have been successfully synthesized and characterized. Single-crystal X-ray analysis revealed that compounds 1 and 2 both contain two eight-coordinated lanthanide (LnIII) ions in the center of them, and adjacent LnIII ions in them are linked together by two μ2-O atoms, generating into a [Ln2O2] cluster. The magnetic studies revealed 1 possesses magnetocaloric effect with the maxmium value of −ΔSm being 17.69 J K−1 kg−1 for ΔH = 8 KOe at 2.0 K. Alternating-current (ac) magnetic susceptibilities studies revealed that 2 displays slow magnetic relaxation behaviors with the anisotropic barrier ΔE/kB = 18.3 K and τ0 = 7.34 × 10−7 s under 5000 Oe.