GdIII Ions Research Articles

NiII‐LnIII Heterometallic Complexes as Single‐Molecule Magnets

This article deals with the synthesis, structural characterization, and magnetic studies of heterometallic NiII/LnIII complexes. The article begins with an introduction on the phenomenon of single‐molecule magnetism and various types of molecular complexes that can function as molecular magnets. Among such complexes, 3d/4f combinations have been studied considerably, although examples involving NiII are considerably fewer than those involving ions like MnIII. In this article, we discuss how NiII can be profitably used to construct molecular magnets by describing features that allow this ion to exhibit magnetic anisotropy. Several examples of NiII/4f complexes drawn from the literature and our own work are described. In most of these complexes, NiII is six‐coordinate in a distorted octahedral geometry, while in one example NiII is four‐coordinate in a square‐planar geometry. The various ligands involved in assembling such diverse complexes are also discussed. In each case the magnetic properties of the complexes, including some SMM properties in particular, are discussed. In view of the isotropic nature of the GdIII ion with seven unpaired f electrons, some NiII/GdIII complexes possessing interesting magnetocaloric properties are also included.

A series of two-dimensional lanthanide coordination polymers: synthesis, structures, magnetism and selective luminescence detection for heavy metal ions and toxic solvents.

A series of two-dimensional (2D) coordination polymers (CPs), namely poly[[bis(μ-acetato)diaqua(μ6-biphenyl-3,3',5,5'-tetracarboxylato)bis(N,N-dimethylacetamide)digadolinium(III)] N,N-dimethylacetamide monosolvate], {[Gd2(C16H6O8)(C2H3O2)2(C4H9NO)2(H2O)2]·C4H9NO}n (CP1), poly[[bis(μ-acetato)diaqua(μ6-biphenyl-3,3',5,5'-tetracarboxylato)bis(N,N-dimethylacetamide)didysprosium(III)] N,N-dimethylacetamide monosolvate], {[Dy2(C16H6O8)(C2H3O2)2(C4H9NO)2(H2O)2]·C4H9NO}n (CP2), poly[bis(μ-acetato)diaqua(μ6-biphenyl-3,3',5,5'-tetracarboxylato)bis(N,N-dimethylacetamide)dineodymium(III)], [Nd2(C16H6O8)(C2H3O2)2(C4H9NO)2(H2O)2]n (CP3), poly[bis(μ-acetato)diaqua(μ6-biphenyl-3,3',5,5'-tetracarboxylato)bis(N,N-dimethylacetamide)disamarium(III)], [Sm2(C16H6O8)(C2H3O2)2(C4H9NO)2(H2O)2]n (CP4), has been synthesized from rigid biphenyl-3,3',5,5'-tetracarboxylic acid under solvothermal conditions. Their structures have been determined by single-crystal X-ray diffraction analyses, elemental analyses, IR spectra, powder X-ray diffraction and thermogravimetric analyses, and CP1-CP4 crystallize in the monoclinic space group P21/n. CP1-CP4 are isomorphous and feature similar 2D double layers, which are further extended via interlayer hydrogen-bonding interactions into a three-dimensional (3D) supramolecular structure. Hydrogen-bonding interactions between N,N-dimethylacetamide molecules and carboxylate O atoms strengthen the packing of the layers. The organic ligands interconnect with metal ions to generate 2D layered structures with a (4,4)-connected net having {44.62} topology. CP1 has been investigated for its magnetic properties and magnetic susceptibility measurements were carried out in the range 2.0-300 K. The results of the magnetic measurements show weak antiferromagnetic coupling between the GdIII ions in CP1. Moreover, the strong luminescence of CP2 and CP4 can be selectively quenched by the Fe3+ ion and toxic solvents (e.g. acetone).

Porous GdIII‐Organic Framework as a Dual‐Functional Material for Cyanosilylation of Aldehydes and Ablation of Human Liver Cancer Cells

Metal‐organic frameworks (MOFs) have gained great attention in recent years because they could behave as multifunctional materials which combine the advances of porous solids and coordination complexes. With the aim of constructing multifunctional MOFs, in this study, we choose a Y‐shaped tricarboxylic ligand biphenyl‐3,4′,5‐tricarboxylic acid (H3bpt) to react with GdIII ions to afford a new dual‐functional lanthanide‐organic framework with the chemical formula of [Gd2(bpt)2(H2O)2]·(DMF)2(H2O)6 (1) (DMF = N,N‐dimethylformamide) under solvothermal condition. The title complex was characterized by means of elemental analysis, FT‐IR spectroscopy, thermogravimetric and X‐ray diffraction analyses. Crystal structure analysis reveals that compound 1 is composed of 1D helical chain secondary building units that connect by the bpt3– ligands into a 3D framework with 1D nanosized channels running along the b axis. In view of its high porosity and accessible open metal sites, the activated 1 (1a) was studied for the cyanosilylation of aldehydes under solvent‐free conditions. The catalytic activity of 1a is much higher than that of compound 1, indicating that the exposed open metal sites of 1a is beneficial to the cyanosilylation reaction. In connection to these, the different cytotoxicities of 1 and 1a were also evaluated on four human liver cancer cells (SMMC‐7721, Bel‐7402, MHCC97 and Hep3B) by the MTT assay.

Tailored ultra-small Prussian blue-based nanoparticles for MRI imaging and combined photothermal/photoacoustic theranostics.

Ultrasmall sub-10 nm nanoparticles of Prussian blue analogues incorporating GdIII ions at their periphery revealed longitudinal relaxivities above 40 mM-1 s-1 per GdIII regardless of the nature of the core and the polymer coating. Large T1-weighted contrast enhancements were achieved in addition to a highly efficient photothermal effect and in vivo photoacoustic imaging in tumors.

Phosphonate-assisted tetranuclear lanthanide assemblies: observation of the toroidic ground state in the TbIII analogue.

The reaction of LnCl3·6H2O with a multidentate flexible Schiff base ligand (LH4), H2O3PtBu and trifluoroacetic acid (tfaH) afforded a series of homometallic tetranuclear complexes, [Ln4(LH2)2(O3PtBu)2(μ2-η1η1tfa)2][2Cl] (Ln = DyIII (1), TbIII (2) and GdIII (3)). The tetranuclear lanthanide core contains two structurally different lanthanide centres, one being in a distorted trigonal dodecahedron geometry and the other in a distorted trigonal prism. Complexes 1-3 were investigated via direct and alternating current (DC and AC) magnetic susceptibility measurements. Only 1 revealed a weak single-molecule magnet (SMM) behaviour. Alternating current (ac) magnetic susceptibility measurements on 1 reveal a frequency-dependent out-of-phase signal. However, the absence of distinct maxima in the χ'' peak (within the temperature/frequency range of our experiments) prevented deduction of the experimental energy barrier for magnetization reversal (Ueff) and the relaxation time. We have carried out extensive ab initio (CASSCF + RASSI-SO + SINGLE_ANISO + POLY_ANISO) calculations on complexes 1-2 to gain deeper insights into the nature of magnetic anisotropy. Our calculations yielded only one exchange coupling parameter between the two LnIII centres bridged by the ligand (neglecting the exchange between the LnIII centres that are not proximal wrt each other). All the extracted J values indicate a weakly antiferromagnetic coupling between the metal centres (J = -0.025 cm-1 for 1 and J = -0.015 cm-1 for 2). Calculated exchange coupled Ucal values of ∼5 and ∼1 cm-1 in 1 and 2 respectively nicely corroborated the experimental observations regarding weak and no SMM characteristics. Our calculations indicated the presence of a net single-molecule toroidal (SMT) behaviour in complex 2. On the other hand, fitting the magnetic data (susceptibility and magnetization) in the isotropic cluster 3 revealed weak AFM exchange couplings of J1 = 0.025 cm-1 and J2 = -0.020 cm-1 which are consistent with those for GdIII ions.

Effects of the Exchange Coupling on Dynamic Properties in a Series of CoGdCo Complexes.

Reaction of 2-hydroxy3-methoxybenzaldehyde ( o-vanillin) with 1,1,1-tris(aminomethyl)ethane, Me-C(CH2NH2)3, or with N, N', N''-trimethylphosphorothioic trihydrazide, P(S)[NMe-NH2]3, yields two tripodal LH3 and L1H3 ligands which are able to give cationic heterotrinuclear [LCoGdCoL]+ or [L1CoGdCoL1]+ complexes. The CoII ions are coordinated to these deprotonated ligands in the inner N3O3 site, while the GdIII ion is linked to three deprotonated phenoxo oxygen atoms of two anionic [LCo]- or [L1Co]- units. Air oxidation of these trinuclear complexes does not yield complexes associating CoIII and GdIII ions. With the first ligand, the structurally characterized resulting complex is the neutral mononuclear LCoIII compound, while in the second case, oxidation of the CoII ions turned out to be impossible. The [L1CoLnCoL1]+ complexes behave as single-molecule magnets with effective energy barriers for the reversal of magnetization varying from Ueff = 51.3 K, τo = 2 × 10-6 s for the yttrium complex to Ueff = 29.5, 29.4, 27.4 K and τo = 1.3 × 10-7, 1.47 × 10-7, 1.50 × 10-7 s for the gadolinium ones, depending on the used counteranions. The energy decrease is compensated by the suppression of quantum tunneling of magnetization in absence of applied field, thanks to the introduction of a ferromagnetic Co-Gd interaction. Current work also shows that uncritical use of conventional spin Hamiltonians, based on quenched orbital momenta, can be misleading and that ab initio calculations are indispensable for establishing the picture of real magnetic interaction. Ab initio calculations show that the CoII sites in the investigated compounds possess large unquenched orbital moments due to the first-order spin-orbit coupling resulting in strongly axial magnetic anisotropy. Although the CoII ions are not axial enough for showing slow relaxation of magnetization by themselves, blocking barriers of exchange type are obtained thanks to the exchange interaction with GdIII ions.

The First Series of Heterometallic LnIII‐VIV Complexes Based on Substituted Malonic Acid Anions: Synthesis, Structure and Magnetic Properties

The reaction of VOSO4 with K2cbdc (cbdc2– is cyclobutane‐1,1‐dicarboxylate anion) and Ln(NO3)3 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Tm, Yb, Lu) yielded 17 novel heterometallic LnIII‐VIV compounds comprising stable bis‐chelate units {VIVO(cbdc)2(H2O)}. Three structural types of compounds are formed depending on the nature of the rare‐earth metal: 1D polymers {[Ln(VO)(cbdc)2(H2O)7]·0.5[VO(cbdc)2]}n (structural type I) [Ln = La (1), Ce (2)], 3D polymers {[KLn(VO)2(cbdc)4(H2O)9]·3.5H2O}n (structural type II) [Ln = La (3), Ce (4), Pr (5), Nd (6), Sm (7), Eu (8), Gd (9), Tb (10), Dy (11), Ho (12)] comprising trinuclear units {LnV2}, and octanuclear complexes {[KLn(VO)2(cbdc)4(H2O)11]·2H2O}2 (structural type III) [Ln = Y (13), Er (14), Tm (15), Yb (16), Lu (17)] containing dinuclear units {LnV}. Magnetic properties were investigated for all isolated compounds. The GdIII‐VIV compound has ferromagnetic and antiferromagnetic exchange interactions between isotropic VIV and GdIII ions. Calculations using the DFT method at the UB3LYP/6‐31G(d,p)/SDD level of theory were performed in order to explain the different nature of exchange interactions in two GdIII‐VIV pairs. The YbIII‐VIV complex displays single‐molecule magnet properties; the effective energy barrier was estimated at ΔEeff/kB = 26 K. The magnetic properties of LnIII‐VIV compounds with heavy lanthanide ions (LnIII = Er, Tm, Yb) were rationalized in terms of crystal‐field calculations for LnIII ions.

Tuning the Topology from fcu to pcu: Synthesis and Magnetocaloric Effect of Metal–Organic Frameworks Based on a Hexanuclear Gd(III)-Hydroxy Cluster

Two polynuclear, cluster-based metal–organic frameworks (MOFs), formulated as {H2[Gd6(OH)8(H2O)6(p-BDC-F4)6]·3(2,2′-bpy)·6H2O} (1) and {H2[Gd6(OH)8(H2O)6(m-BDC-F4)6]·3(4,4′-bpy)·6H2O} (2) (p-BDC-F4 = tetrafluoroterephthalic acid, m-BDC-F4 = tetrafluoroisophthalic acid), are synthesized by hydrothermal reactions of GdIII ions with perfluorinated benzenedicarboxylate. Structure analysis illustrates that both 1 and 2 are constructed by the hexanuclear GdIII-hydroxy cluster molecular building block {Gd6(OH)8(COO)12(H2O)6}, generating a 12-connected fcu-MOF and a 6-connected pcu-MOF, respectively. Compounds 1 and 2 are stable in some refluxing organic solvents, boiling water, and aqueous solutions in the pH range of 2–11. Notably, magnetic investigation indicates that 1 and 2 display a significant magnetocaloric effect.

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.

A Chiral Bipyrimidine-Bridged Dy2 SMM: A Comparative Experimental and Theoretical Study of the Correlation Between the Distortion of the DyO6N2 Coordination Sphere and the Anisotropy Barrier.

Chiral bipyrimidine-bridged dinuclear LnIII complexes of general formula [(μ-bipym){((+)-tfacam)3Ln}2] and [(μ-bipym){((-)-tfacam)3Ln}2], have been prepared from the assembly of Ln(AcO)3·nH2O (LnIII = Dy, Gd), (+)/(−)-3-(trifluoroacetyl)camphor enantiopure ligands ((+)/(-)-Htfacam) and bipyrimidine (bipym). The structure and chirality of these complexes have been supported by single-crystal X-Ray diffraction and circular dichroism. The study of the magnetic properties of the GdIII complexes revealed a very weak antiferromagnetic interaction between the GdIII ions through the bipyrimidine bridging ligand. Ab initio CASSCF calculations indicated that the ground Kramers doublet (KD) of both DyIII centers is almost purely axial with the anisotropy axis located close to the two tfacam−ligands at opposite sides of each DyIIIatom, which create an axial crystal field. In keeping with this, ac dynamic measurements indicated slow relaxation of the magnetization at zero field with Ueff = 55.1 K, a pre-exponential factor of τo = 2.17·10−6 s and τQTM = 8 μs. When an optimal dc field of 0.1 T is applied, QTM is quenched and Ueff increases to 75.9 K with τo = 6.16 × 10−7 s. The DyN2O8 coordination spheres and SMM properties of [(μ-bipym){((+)-tfacam)3Ln}2] and their achiral [(Dy(β-diketonate)3)2(μ-bpym)]analogous have been compared and a magneto-structural correlation has been established, which has been supported by theoretical calculations. In contrast to the GdIII compounds, the magnetic exchange interaction between the DyIII ions has been calculated to be very weak and, generally, ferromagnetic in nature. Relaxation mechanisms for [(μ-bipym){((+)-tfacam)3Ln}2] and previously reported analogous have been proposed from ab initio calculations. As the magnetic exchange interaction found to be very weak, the observed magnetization blockade in these systems are primarily dictated by the single ion anisotropy of DyIII ions.

Synthesis, structures and magnetic refrigeration of two rhombus-shaped Gd4 cages

Two new Gd4 cages based on 8-hydroxyquinoline Schiff base ligand and β-diketonate auxiliary ligands have been obtained and magnetically characterized. The X-ray structural analysis exhibit that both cages 1 and 2 contain one Gd4 molecule with a rhombus-shaped arrangement, and each GdIII ion of them is located in a distorted square-antiprismatic coordination sphere. Magnetic properties measurement indicate that weak antiferromagnetic interactions were existed between the GdIII ions in 1 and 2, and they display magnetic refrigeration with −ΔSm = 21.95 J kg−1 K−1 for 1(ΔH = 7 T and T = 2.0 K) and −ΔSm = 15.02 J kg−1 K−1 for 2 (ΔH = 7 T and T = 3.0 K).

Insulin Hexamer-Caged Gadolinium Ion as MRI Contrast-o-phore.

High-relaxivity protein-complexes of GdIII are being pursued as MRI contrast agents in hope that they can be used at much lower doses that would minimize toxic-side effects of GdIII release from traditional contrast agents. We construct here a new type of protein-based MRI contrast agent, a proteinaceous cage based on a stable insulin hexamer in which GdIII is captured inside a water filled cavity. The macromolecular structure and the large number of "free" GdIII coordination sites available for water binding lead to exceptionally high relaxivities per one GdIII ion. The GdIII slowly diffuses out of this cage, but this diffusion can be prevented by addition of ligands that bind to the hexamer. The ligands that trigger structural changes in the hexamer, SCN- , Cl- and phenols, modulate relaxivities through an outside-in signaling that is allosterically transduced through the protein cage. Contrast-o-phores based on protein-caged metal ions have potential to become clinical contrast agents with environmentally-sensitive properties.

A Series of Lanthanide Compounds Constructed from Ln8 Rings Exhibiting Large Magnetocaloric Effect and Interesting Luminescence.

A series of lanthanide compounds, [Ln8(CH2OHCH2OH)8(SO4)12]· m(C2H7N)· nH2O (Ln = Gd (1), Sm (2), Tb (3), La (5), m = 2, n = 2; Ln = Eu (4), m = 0, n = 8), which contain Ln8 rings by sulfate and glycol as the ligand have been synthesized and characterized. Besides, small organic amine and l-tartaric acid act as dual templating roles during the synthetic process. Magnetic investigation of compound 1 reveals the existence of weak antiferromagnetic interactions between GdIII ions and the data of magnetic entropy change (-Δ Sm) is 36.86 J K-1 kg-1 (108.55 mJ cm-3 K-1) for Δ H = 7 T at 2.0 K, which is comparatively large among GdIII based compounds. Additionally, because of the excellent luminescence properties of SmIII, TbIII, and EuIII, compounds 2-4 were investigated.

Hydrothermal synthesis, crystal structure, luminescent and magnetic properties of a new mononuclear GdIII coordination complex

A new GdIII coordination complex, {[Gd(2-stp)2(H2O)6].2(4,4'-bipy).4(H2O)}, complex 1, (2-stp = 2-sulfoterephthalate anion and 4,4'-bipy = 4,4'-bipyridine), has been synthesized by hydrothermal method and characterized by elemental analysis, solid state UV–Vis and FT-IR spectroscopy, single-crystal X-ray diffraction, solid state photoluminescence and variable-temperature magnetic measurements. The crystal structure determination shows that GdIII ions are eight coordinated and adopt a distorted square-antiprismatic geometry. Molecules interacting through intra- and intermolecular (O-H⋯O, O-H⋯N) hydrogen bonds in complex 1, give rise to 3D hydrogen bonded structure and the discrete lattice 4,4'-bipy molecules occupy the channel of the 3D structure. π-π stacking interactions also exist 4,4'-bipy-4,4'-bipy and 4,4'-bipy-2-stp molecule rings in 3D structures. Additionally, solid state photoluminescence properties of complex 1 at room temperature have been investigated. Under the excitation of UV light (at 349 nm), the complex 1 exhibited green emissions (at 505 nm) of GdIII ion in the visible region. Furthermore, Variable-temperature magnetic susceptibility and isothermal magnetization as function of external magnetic field studies reveal that complex 1 displays possible antiferromagnetic interaction.

Three Phenoxo‐Bridged Dinuclear Lanthanide Complexes: Syntheses, Crystal Structures, and Magnetic Properties

Three dinuclear lanthanide complexes [Ln2(H2L)2(NO3)4] [Ln = Dy (1), Tb (2), and Gd (3)] [H3L = 2‐hydroxyimino‐N′‐[(2‐hydroxy‐3‐methoxyphenyl)methylidene]‐propanohydrazone] were solvothermally synthesized by varying differently anisotropic rare earth ions. Single‐crystal structural analyses demonstrate that all the three complexes are crystallographically isostructural with two centrosymmetric LnIII ions aggregated by a pair of monodeprotonated H2L– anions. Weak intramolecular antiferromagnetic interactions with different strength were mediated by a pair of phenoxo bridges due to superexchange and/or single‐ion anisotropy. Additionally, the DyIII‐based entity shows the strongest anisotropy exhibits field‐induced single‐molecule magnetic behavior with two thermally activated relaxation processes. In contrast, 3 with isotropic GdIII ion has a significant cryogenic magnetocaloric effect with the maximum entropy change of 25.7 J·kg–1·K–1 at 2.0 K and 70.0 kOe.

Role of (1,3) {Cu-Cu} Interaction on the Magneto-Caloric Effect of Trinuclear {CuII-GdIII-CuII} Complexes: Combined DFT and Experimental Studies.

Molecular refrigeration is found to be of great interest in the field of coordination chemistry, and GdIII ion based complexes are particularly attractive, as they exhibit a large magneto-caloric effect (MCE). As the magnetic coupling in GdIII clusters is difficult to control, other avenues to enhance the MCE values have been explored and incorporation of 3d metal ions in the cluster aggregation with GdIII yielding {3d-Gd} clusters are targeted. Among the transition-metal ions, the CuII ion is particularly attractive, as it does not possess any anisotropy, and in this regard, several di- and polynuclear {Cu-Gd} clusters are reported to yield attractive MCE values. While the role of near-neighbor {Cu-Gd} interactions in the MCE has been explored in detail, how the next-nearest-neighbor interaction influences the MCE has not been explored. To explore the importance of next-nearest-neighbor (1,3) {Cu-Cu} interaction, we have undertaken detailed density functional studies on five trinuclear {CuII-GdIII-CuII} complexes that are reported in the literature. In addition, we also report the synthesis and magnetic and EPR studies of a novel complex [(CuSALen)2Gd(NO3)3] (6; where SALen is N,N'-ethylenebis(salicylaldiminato)). Both magnetic and EPR studies reveal an S = 9/2 ground state for 6 with a very small zero-field splitting parameter (+0.01 cm-1), which aid in the achievement of a large MCE value for this molecule. Magnetization data collected for 6 yield a magnetic entropy change (-ΔSm) of 17 J kg-1 K-1 at 3.5 K by employing a 7 T magnetic field. Our calculations on all six complexes reveal that {Cu-Gd} exchange is ferromagnetic in nature, while the next-nearest-neighbor {Cu-Cu} exchange is found to vary from a weak ferromagnetic to a moderate antiferromagnetic interaction. In all of the cases studied, simulated susceptibility data are in excellent agreement with the experimental data, offering confidence in the computed J values. In addition, we have developed a mechanism of magnetic coupling for {CuII-GdIII-CuII} trinuclear complexes, where the role of formally empty 5d, 6s, and 6p orbitals of GdIII ion is established. In particular, our studies reveal that the next-nearest-neighbor {Cu-Cu} interaction is strongly correlated to Cu-Gd-Cu angle, with both smaller and larger angles yielding stronger antiferromagnetic exchange. The antiferromagnetic {Cu-Cu} interaction diminishes the gap between the ground S = 9/2 state and first excited S = 7/2 state, leading to enhancement of MCE values. In contrast to the general belief that weak interactions are desired for large MCE, our study advocates targeting a stronger antiferromagnetic {Cu-Cu} interaction to obtain larger MCE values in this class of clusters.

Structural and Magnetic Variations in a Family of Isoskeletal, Oximate-Bridged {MnIV2 MIII } Complexes (MIII =Mn, Gd, Dy).

The self-assembly reaction of MnCl2 ⋅4H2 O, acenaphthenequinone dioxime (acndH2 ) and NEt3 has yielded an unprecedented, linear {MnIV2 MnIII } complex with an S=5 spin ground state and non-SMM behavior. The targeted replacement of the central MnIII ion with GdIII and DyIII ions has successfully increased the S and turned on the SMM dynamics without affecting the core structure and the nature of the magnetic exchange interactions.

Heterometallic lanthanide-centred [NiLnIII] rings.

A [NiII6DyIII] heptanuclear complex featuring a rare six-membered {NiII6} metal ring surrounding the central Dy(iii) ion is reported. Magnetic studies reveal single-molecule magnet behaviour for the complex under zero external dc field, while replacing the DyIII ion with [capital Upsilon]III or GdIII ions allows for a comprehensive understanding of the magnetic behaviour.

Three microporous metal-organic frameworks assembled from dodecanuclear {NiLn} subunits: synthesis, structure, gas adsorption and magnetism.

Three isostructural heterometallic metal-organic frameworks (MOFs) {[Ln2Ni(OAc)5(HL)(L)]·solvent molecules}n (H2L = 2-hydroxyimino-N-[1-(2-pyrazinyl)ethylidene]-propanohydrazone, Ln = Dy for 1, Tb for 2 and Gd for 3) were solvothermally synthesized by varying rare-earth metal ions with different electron configurations. Their crystal structures, gas adsorption and magnetic behaviors were fully investigated. The three isomorphous MOFs exhibit three-dimensional microporous frameworks with two different orientated dodecane metallic {NiIILnIII(HL)}6 metallomacrocycles alternately connected by {LnIII(L)} connectors, in which an empty one-dimensional channel decorated by the basic hydrazone interior is generated. Due to their LnIII-independent microporous nature, the activated sample of 1 as a representative example has a significant CO2 uptake up to 42.2 cm3 g-1 and an unusually high CO2/N2 and CO2/CH4 adsorption selectivity of up to 98.8 and 16.8 at 298 K and 100 kPa. Magnetically, apparent antiferromagnetic interactions for both 1 and 2 as well as ferromagnetic coupling for 3 are respectively observed at low temperature resulting from the competition of magnetic anisotropy and intermetallic ferromagnetic superexchange. Additionally, 1 with highly anisotropic DyIII spin shows slow magnetization relaxation under zero dc field, whereas 3 possessing isotropic GdIII ions displays a significant cryogenic magnetocaloric effect with a maximum entropy change of 26.6 J kg-1 K-1 at 3.0 K and 70 kOe. These interesting results can provide valuable information on gas separation-based multifunctional 3d-4f MOF materials.

Synthesis, Structure, and Magnetic Properties of a Family of Complexes Containing a {CoII2DyIII} Pivalate Core and a Pentanuclear CoII4DyIII Derivative

A series of new CoII–LnIII complexes with polynuclear {Co2Ln(NO3)(Piv)6} (Ln = La, Gd, Dy; Piv = pivalate) cores were prepared by self‐assembly reactions or step‐by‐step assembly. [Co2Dy(NO3)(Piv)6(MeCN)2] was used as the starting compound for the synthesis of the trinuclear analogue [Co2Dy(NO3)(Piv)6(py)2] (py = pyridine) and the pentanuclear complex [{Co2Dy(NO3)(Piv)6}{CoL(Piv)(H2O)}2][NO3]2 [L = 2,6‐bis(2‐pyridyl)‐4‐(4‐pyridyl)pyridine]. The effects of the coordination environment and temperature on the distortion of the LnIII coordination polyhedra were analyzed for a series of coordination compounds with MII2LnIII cores and close analogues. The distortion of the LnIII polyhedron depends on both the composition of the compound and the temperature; a temperature increase favors the D2d geometry of the LnIII coordination polyhedron. The magnetic properties of the complexes with CoII2DyIII cores were analyzed with consideration of the anisotropy of the CoII and DyIII ions. The compounds containing diamagnetic LaIII and isotropic GdIII ions, [Co2Ln(Piv)6(NO3)(MeCN)2] (Ln = La, Gd), which are isostructural to the CoIIDyIII analogue, were studied to evaluate the CoII magnetic‐anisotropy parameters to minimize the overparameterization of the magnetic properties in the fits for the Co2Dy systems. The magnetic properties of all complexes in this study are governed mainly by the magnetic properties of the isolated ions.