Adjacent Gd Research Articles

The adjacent effect between Gd(III) and Cu(II) in layered double hydroxide nanoparticles synergistically enhances T1-weighted magnetic resonance imaging contrast.

Magnetic resonance imaging (MRI) is one key technology in modern diagnostic medicine. However, the development of high-relaxivity contrast agents with favorable properties for imaging applications remains a challenging task. In this work, dual Gd(III) and Cu(II) doped-layered double hydroxide (GdCu-LDH) nanoparticles show significantly higher longitudinal relaxivity compared with sole-metal-based LDH (Gd-LDH and Cu-LDH) nanoparticles. This relaxation enhancement in GdCu-LDH is also much greater than the simple addition of the relaxivity rate of the two paramagnetic ions in Gd-LDH and Cu-LDH, presumably attributed to synergistic T1 shortening between adjacent Gd(III) and Cu(II) in the LDH host layers (adjacent effect). Moreover, our GdCu-LDH nanoparticles exhibit a pH-ultrasensitive property in MRI performance and show much clearer MR imaging for tumor tissues in mice than Gd-LDH and Cu-LDH at the equivalent doses. Thus, these novel Gd/Cu-co-doped LDH nanoparticles provide higher potential for accurate cancer diagnosis in clinic application. To the best of our knowledge, this is the first report that two paramagnetic metal ions in one nanoparticle synergistically improve the T1-MRI contrast.

Tridecanuclear Gd(III)-silsesquioxane: Synthesis, structure, and magnetic property

Polynuclear metal clusters, particularly those with aesthetically appealing structures, are of increasing interest. In this study, by employing C 4 symmetrical macrocyclic silsesquioxane ligand, a novel tridecanuclear Gd(III) cluster ( Gd13 ) with a {Gd 13 O 8 } core featuring unprecedent body-centered Archimedean cuboctahedron conformation is realized using an efficient solvothermal method instead of conventional Schlenk techniques. To the best of our knowledge, Gd13 cluster is thus far the highest nuclearity of lanthanide-silsesquioxane. Moreover, a magnetic study reveals a weak antiferromagnetic interaction between adjacent Gd ions in the cluster. In addition, Gd13 exhibits cryogenic magnetocaloric effects with a maximum −Δ S M value of 20 J kg −1 K −1 at 2 K and Δ H = 7.0 T.

A Solvent-Stable Zinc(II)–Gadolinium(III) Metal–Organic Framework Assembled with Furan-2,5-Dicarboxylic Acid: Synthesis, Crystal Structure and Magnetic Property

A novel three-dimensional 3d–4f metal–organic framework (MOF), {[(CH3)2NH2]2[Zn2Gd2(FDA)6(DMF)2]·2DMF}n (Zn–Gd) (H2FDA = furan-2,5-dicarboxylic acid) assembled with furan-2,5-dicarboxylic acid has been isolated and characterized by infrared spectra, elemental analysis, thermogravimetric analysis, powder X-ray diffraction and single-crystal X-ray diffraction. Structure analysis indicates this MOF is an interesting three-dimensional 8-connected bcu body centered cubic topological net. Moreover, Zn–Gd MOF shows a tolerance towards moisture and the corresponding solvents, demonstrating the excellent chemical stability. The magnetic property of Zn–Gd MOF suggests a weak antiferromagnetic coupling interaction between adjacent Gd(III) ions in Zn–Gd MOF.

Proximity effect induced enhanced spin pumping in Py/Gd at room temperature

We report on ferromagnetic resonance spectroscopy studies of Py/Gd system by varying thickness of Gd layer. We found that a portion of the Gd layer at the interface becomes ferromagnetically ordered at room temperature and become antiferromagnetic coupled to the Py due to the magnetic proximity effect, as evidenced by a Gd-thickness dependent shift in the resonance field and exchange bias field. We show a large increase in the effective Gilbert damping of the Py layer when the thickness of the adjacent Gd layer is increased. We argue that a major contribution of this increase is due to the spin pumping effect into the ordered ferromagnetic Gd layer.

Synthesis, characterization, and properties of four lanthanide-based coordination polymers with mixed ligands of 4-((4′-carboxybenzyl)oxy)benzoic acid and oxalic acid

A series of lanthanide-based coordination polymers (Ln2(CBOB)2(OX)·H2O, where Ln = Gd (1), Eu (2), Pr (3), and Tb (4); CBOB = 4-[(4′-carboxybenzyl)oxy]benzoate; OX = oxalate), were obtained from the reaction of H2OX, H2CBOB, and Ln(NO3)3 with the metal salts. Single-crystal measurements show that both 1 and 2 feature unique 3-D structures with the [Ln(COO)n(C2O4)m] layers connected by CBOB ligands. Moreover, 1, 3, and 4 are antiferromagnetic and 2 and 4 display obvious luminescence emission peaks. Furthermore, quantum Monte Carlo (QMC) simulations and the experimental results reveal that the magnetic coupling parameters of adjacent Gd(III) ions in 1 are −0.026(2) and −0.0069(3) cm─1.

Two unique hydroxyl bridged lanthanide polymers incorporating mixed carboxylate ligands: Syntheses, structures, luminescence and magnetic property

Two lanthanide–organic coordination polymers incorporating both substituted imdazole dicarboxylate and benzene monocarboxylate auxiliary ligand, namely, {[Gd2(μ3-OH)(pimda)(imba) (H2pimda) H2O]·2H2O}n (1) and {[Tb2((μ3-OH)(pimda)(imba) (H2pimda) H2O]·2H2O}n (2) (H3pimda=2-propyl-1H-imidazole-4,5-dicarboxylic acid and H2imba=4-(1H-imidazole-1-ly) benzoic acid) have been obtained under the hydrothermal conditions, and have been structurally characterized by elemental analysis, IR spectrum and single X-ray diffraction. The polymers are isostructural, both crystallizing in the triclinic system, with space group of p-1. They display one dimensional (1-D) double-stranded ribbon chains based on hydroxyl-bridged [Ln4pimda2] tetranuclear unit as second building block, which are interlinked forming 2-D corrugated layer. The extensive hydrogen bondings further extend these 2-D lamellar networks into 3-D supramolecular architecture. The emission spectrum of polymer 1 exhibits ligand-to-ligand charge-transfer (LLCT) transition luminescence; polymer 2 shows characteristic f-f transition luminescence, which can be considered as a fluorescent molecular sensor for zinc(II) ions in environment. Variable-temperature magnetic susceptibility measurement reveals that multi-bridging fashion of carboxylic group in 1 results in depopulation of the stark levels for a single Gd(III) ion and/or possible antiferromagntic interactions between adjacent Gd(III) cations within the carboxylato bridged binuclear unit.

Lanthanide Coordination Polymers with 4,4'-Azobenzoic Acid: Enhanced Stability and Magnetocaloric Effect by Removing Guest Solvents.

Three lanthanide coordination polymers (Ln-CPs) formulated as [Ln(azdc)(HCOO)]n [Ln = Gd(III) (1), Tb(III) (2), Dy(III) (3); H2azdc = 4,4'-azobenzoic acid] have been successfully obtained by the solvothermal reaction of Ln(III) ions with H2azdc ligands in the mixed solvent N,N-dimethylformamide (DMF)/H2O. Compared with our previous work on Ln-CPs with H2azdc ligands, [Gd2(azdc)3(DMA)2]n·2nDMA (1'; DMA = dimethylacetamide), in which the DMA molecules coordinate to Gd(III) ions that are replaced by HCOO(-) groups in 1, resulting in the distinct structures and properties of the final products. Adjacent Ln(III) ions in 1-3 are connected by HCOO(-) groups through bridging and chelating modes to give 2D layers, which are further linked by azdc(2-) ligands to produce 3D frameworks. Magnetic results declare that antiferromagnetic couplings exist in 1, although two different magnetic interactions among adjacent Gd(III) ions derived from antiferromagnetic interactions of the smaller Gd-O-Gd angles (Gd···Gd distances) and weak ferromagnetic interactions of the larger Gd-O-Gd angles (Gd···Gd distances) coexist in 1. Furthermore, the magnetocaloric effect (MCE) value of 1 is 1.5 times as large as that of 1'. More importantly, 1 exhibits excellent stabilities toward air, thermal, solvent, and acid/alkaline conditions. The results manifest that the crystalline structure of 1 can be stable at at least 425 °C supported by the in situ variable-temperature powder X-ray diffraction patterns and thermogravimetric analyses, in air for at least 3 months, and in common solvents for more than 1 week, as well as in aqueous solutions ranging from pH = 2 to 12 for more than 1 week.

Lanthanide coordination polymers with "fsy-type" topology based on 4,4'-azobenzoic acid: syntheses, crystal structures, and magnetic properties.

Seven lanthanide coordination polymers (CPs), [Ln2(azdc)3(DMA)2]n·2n(DMA) (Ln = Sm(III) for 1, Eu(III) for 2, Gd(III) for 3, Tb(III) for 4, Dy(III) for 5, Ho(III) for 6, Er(III) for 7; H2azdc = 4,4'-azobenzoic acid, DMA = N,N-dimethylacetamide), have been successfully prepared with high yields via solvothermal methods and further studied by elemental analyses (EA), powder X-ray diffraction (PXRD), UV-vis spectra, photoluminescent spectra, thermogravimetric analyses (TGA), variable-temperature in situ PXRD analyses, and single-crystal X-ray diffraction. CPs 1-7 all consist of unique 1D lanthanide-carboxylate building units [Ln2(CO2)6]n constructed from the adjacent Ln(III) cations and carboxyl groups of the H2azdc ligands, which can further generate 3D frameworks with "fsy"-type topological structures via the link of azdc(2-). Furthermore, variable-temperature magnetic susceptibility measurements of 1-7 have been investigated. The results indicate that unusual ferromagnetic coupling between adjacent Gd(III) cations exists in 3, which is rarely reported in the Gd(III) complexes only bridged by μ1,3-COO groups. Meanwhile, the magnetic study reveals that 3 displays cryogenic magnetic refrigeration property, whereas 5 shows magnetic dynamics at low temperature.

Density functional calculations for structural, electronic, and magnetic properties of gadolinium-oxide clusters

Gadolinium-oxide clusters in various sizes and stoichiometries have been systematically studied by employing the density functional theory with the generalized gradient approximation. The clusters in bulk stoichiometry are relatively more stable and their binding energies increase with the increasing size. Stoichiometric (Gd2O3)n clusters of n = 1–3 prefer cage-like structures, whereas the clusters of n = 4–30 prefer compact structures layered by wedge-like units and exhibit a rough feature toward the bulk-like arrangement with small disorders of atomic positions. The polyhedral-cages analogous to carbon-fullerenes are stable isomers yet not the minimum energy configurations. Their stabilities can be improved by embedding one oxygen atom or a suitable cage to form core-shell configurations. The mostly favored antiferromagnetic couplings between adjacent Gd atoms are nearly degenerated in energy with their ferromagnetic couplings, resulting in super-paramagnetic characters of gadolinium-oxide clusters. The Ruderman-Kittel-Kasuya-Yosida (RKKY)-type mechanism together with the superexchange-type mechanism plays cooperation role for the magnetic interactions in clusters. We present, as a function of n, calculated binding energies, ionization potential, electron affinity, and electronic dipole moment.

Substitution of gadolinium ethylenediaminetetraacetate with phosphites: towards gadolinium deposit in nephrogenic systemic fibrosis

In neutral media, reactions of gadolinium ethylenediaminetetraacetates with phosphorous acid result in the formation of the mixed-ligand polymeric complex K3n[Gd(EDTA)(HPO3)]n·7nH2O () and dimeric complex Na6[Gd2(EDTA)2(HPO3)2]·2.5NaCl·21H2O () (H4EDTA = ethylenediaminetetraacetic acid) in warm solution. Further substitution with citric acid gives the monomeric gadolinium citrate with EDTA (NH4)2Na[Gd(EDTA)(H2cit)]·4H2O (). The compounds were characterized by elemental analysis, single crystal X-ray diffraction, FT-IR, ESI-MS and thermogravimetric analysis. Structural analysis indicates that three coordinated water molecules in the gadolinium ethylenediaminetetraacetate trihydrates are replaced by phosphite ions (HPO3(2-)) in the compounds and . Gadolinium atoms are octa-coordinated by EDTA and the phosphite ion, the latter links adjacent Gd-EDTA units to generate an infinite one-dimensional chain in compound and a dimeric octatomic ring in . In complex , coordinated water molecules were substituted by the α-hydroxy, α-carboxy and β-carboxy groups of citrate. Citrate is favourable for inhibiting the formation of Gd-EDTA phosphite. All the complexes are very easily soluble in water. The solution behavior of the isostructural lanthanum complexes was probed with (13)C and (31)P NMR spectra in D2O for comparison. ESI-MS analysis and recrystallization proved that complexes and dissociate to the monomeric unit of Gd-EDTA and free HPO3(2-) in aqueous solution. Substitutions of gadolinium ethylenediaminetetraacetates to and are attributed to be the cause of nephrogenic systemic fibrosis in some way.

Electronic and magnetic structures of GdS layers investigated by first principle and series expansions calculations

Self-consistent ab initio calculations, based on Density Functional Theory (DFT) approach and using Full Potential Linear Augmented Plane Wave (FLAPW) method within GGA+U approximation, are performed to investigate both electronic and magnetic properties of the GdS layers. Polarized spin and spin–orbit coupling are included in calculations within the framework of the antiferromagnetic state between two adjacent Gd layers. Magnetic moment considered to lie along (001) axes are computed. Obtained data from ab initio calculations are used as input for the High Temperature Series Expansions (HTSEs) calculations to compute other magnetic parameters.Using the Heisenberg model, the exchange interactions between the magnetic atoms Gd–Gd in the same layer and between the magnetic atoms in the adjacent bilayers are estimated. This estimate is obtained using the antiferromagnetic and ferromagnetic energies computed by abinitio calculations for GdS layers. The High Temperature Series Expansions (HTSEs) of the magnetic susceptibility of GdS with antiferromagnetic moment (mGd) is given up to sixth order series versus of (J11(Gd–Gd)/kBT). The Néel temperature TN is obtained by mean field theory and by HTSEs of the magnetic susceptibility series using the Padé approximant method. The critical exponent γ associated with the magnetic susceptibility is calculated for GdS layers.

Synthesis and magnetic properties of a 3d–4f heterometallic chain

A new 3d–4f heterometallic coordination polymer: [MnIIGd2III(OAc)8(H2O)4]·6H2O (1) (OAc−=acetate), has been conventionally synthesized and characterized by elemental analysis, IR, TG and single crystal X-ray diffraction. In 1, two Gd3+ and one Mn2+ cations are linked by carboxylic bridge of OAc− anions, giving a 1D 3d–4f heterometallic [MnIINd2III(OAc)8(H2O)4] chain. In the chain, there exist the short distances between the adjacent Gd(III) and Mn(II) ions as well as Gd(III) and Gd(III) ions, which make this 1D polymer displaying interesting magnetic properties.

Preparation, crystallographic and theoretical study on a bifunctional Gd-AAZTA derivative as potential MRI contrast agent precursor

The crystal structure of the complex (αR,6R)-Na[Gd(H2O)-AAZTA-C2H4COOBn]·3H2O·EtOH was determined by single crystal X-ray diffraction; the complex represents a bifunctional derivative of Gd-AAZTA, previously reported as original scaffold for the development of efficient contrast agents for MRI. The Gd(III) ion is nine coordinated with three nitrogens, five carboxylate oxygens and one water oxygen in a monocapped distorted square antiprism coordination polyhedron. Three of the five carboxylic groups are monodentate while a fourth is bidentate bridging an adjacent Gd ion with the formation of a polymeric structure. The influence on the overall structure of the propionate side arm introduced for conjugation purposes was discussed, and a computational approach to predict the structure of its (αR,6S) isomer is presented and compared with the X-ray structure of the (αR,6R) epimer.

A Density Functional Theory Study of Gd<sub>8</sub>O<sub>12</sub> Cluster

The spin-polarized generalized gradient approximation to the density functional theory is used to determine the geometries, stability, electronic structures, and magnetic properties of the Gd8O12cluster. Our work reveals that the ground state configuration of the Gd8O12cluster is a hexahedral cage structure with Cisymmetry. The electronic and magnetic properties imply that the formations of the ionic bonds between the adjacent Gd and O atoms result in the high stability of the Gd8O12cluster, which is due to the charge transfers between the Gd 5d, 6s electrons to O 2p orbital. It is also confirmed by the electron densities of HOMO-LUMO states. In addition, the analysis of the magnetic properties implies the total magnetic moments are mostly dominated by the Gd 4f orbital.

Density Functional Theory Study of Magnetic Coupling in the Gd12O18Cluster

The magnetic properties of the Gd(12)O(18) cluster cut from the bulk Gd(2)O(3) crystal are investigated using the spin-polarized density functional theory within the broken-symmetry approach. Our work reveals that in the ground state of the cluster the antiferromagnetic coupling between adjacent Gd (4f(7)) spins is preferred energetically. This result is in contrast to a recent prediction made by Pedersen and Ojamae (Pedersen, H.; Ojamae, L. Nano Lett. 2006, 6, 2004) but is consistent with recent experimental observations. The optimized structures of the cluster in the lowest-energy broken-symmetry state and the highest-spin ferromagnetic state are almost identical. The latter state is 71.5 cm(-1) higher in energy than the former one, giving a value of about -0.24 cm(-1) for the magnetic coupling constant, which is comparable to that estimated from experiments on the bulk crystal. The relative energies of various 4f(7) spin patterns of the cluster are calculated, and certain characteristics of the cluster in the lowest-energy broken-symmetry state are discussed.

Role of Ge in Bridging Ferromagnetism in the Giant MagnetocaloricGd5(Ge1−xSix)4Alloys

X-ray magnetic circular dichroism (XMCD) measurements and density functional theory (DFT) are used to study the electronic conduction states in Gd5(Ge(1-x)Si(x))4 materials through the first-order bond-breaking magnetostructural transition responsible for their giant magnetocaloric effect. Spin-dependent hybridization between Ge 4p and Gd 5d conduction states, which XMCD senses through the induced magnetic polarization in Ge ions, enables long-range Ruderman-Kittel-Kasuya-Yosida ferromagnetic interactions between Gd 4f moments in adjacent Gd slabs connected by Ge(Si) bonds. These interactions are strong below but weaken above the Ge(Si) bond-breaking transition that destroys 3D ferromagnetic order.

Metamagnetism of the First Cyano-Bridged Two-Dimensional Brick-Wall-like 4f−3d Array

[Gd(DMF)2(H2O)3Cr(CN)6]·H2O is the first lanthanide−transition metal array with a flat two-dimensional brick-wall-like molecular structure. The antiferromagnetic coupling between the adjacent Gd−Cr ions leads to intralayer ferrimagnetic correlation due to the noncancellation of spins. The long-range magnetic ordering (TN = 3.5 K) was observed for the first time in low-dimensional cyano-bridged 4f−3d coordination polymers. Metamagnetic behavior was observed at 1.8 K arising from antiferromagnetic coupling between the ferrimagnetic layers.

The magnetic properties of gadolinium/holmium superlattices

The magnetic properties of Gd/Ho superlattices have been investigated using neutron-diffraction techniques. Between and , the magnetic moments in each Gd block order ferromagnetically in the basal plane with the moments in adjacent Gd blocks antiferromagnetically aligned. At temperatures below , the Ho moments order in a basal-plane helix, while the Gd moments remain ferromagnetically aligned in the basal plane with an alignment between adjacent Gd blocks that is dependent on temperature and the Ho-block thickness. The coherence lengths of the magnetic structures in the growth direction range from 350 Å to 800 Å. Comparisons are made with the results from previous studies of heavy rare-earth superlattices.