Xiu-Ying Zheng

Magnetic Properties of a Single‐Molecule Lanthanide–Transition‐Metal Compound Containing 52 Gadolinium and 56 Nickel Atoms

Monodisperse metal clusters provide a unique platform for investigating magnetic exchange within molecular magnets. Herein, the core-shell structure of the monodisperse molecule magnet of [Gd52 Ni56 (IDA)48 (OH)154 (H2 O)38 ]@SiO2 (1 a@SiO2 ) was prepared by encapsulating one high-nuclearity lanthanide-transition-metal compound of [Gd52 Ni56 (IDA)48 (OH)154 (H2 O)38 ]⋅(NO3 )18 ⋅164 H2 O (1) (IDA=iminodiacetate) into one silica nanosphere through a facile one-pot microemulsion method. 1 a@SiO2 was characterized using transmission electron microscopy, N2 adsorption-desorption isotherms, and inductively coupled plasma-atomic emission spectrometry. Magnetic investigation of 1 and 1 a revealed J1 =0.25 cm(-1) , J2 =-0.060 cm(-1) , J3 =-0.22 cm(-1) , J4 =-8.63 cm(-1) , g=1.95, and z J=-2.0×10(-3)  cm(-1) for 1, and J1 =0.26 cm(-1) , J2 =-0.065 cm(-1) , J3 =-0.23 cm(-1) , J4 =-8.40 cm(-1)  g=1.99, and z J=0.000 cm(-1) for 1 a@SiO2 . The z J=0 in 1 a@SiO2 suggests that weak antiferromagnetic coupling between the compounds is shielded by silica nanospheres.

Mixed-anion templated cage-like lanthanide clusters: Gd27 and Dy27

Two nanoscale clusters whose metals are exclusively lanthanides, and whose formulas are [(ClO4)@Ln27(μ3-OH)32(CO3)8(CH3CH2COO)20(H2O)40]·(ClO4)12·(H2O)50 (abbreviated as Ln27. 1, Gd; 2, Dy), were synthesized. Structural analysis showed that the 27 lanthanide ions were organized into a beautiful cage-like structure templated by eight CO32− groups, which were generated from the fixation of atmospheric CO2. Acting as a template guest, one ClO4− group was encapsulated in the Ln27 cage. The Ln27 compound is by far the largest odd-numbered lanthanide cluster synthesized to date. In magnetization studies of these two compounds, isotropic Gd27 exhibited a large MCE of 41.8 J kg−1 k−1 at 2 K for ΔH = 7 T, while anisotropic Dy27 displayed a slow relaxation of its magnetization.

Three Giant Lanthanide Clusters Ln37 (Ln = Gd, Tb, and Eu) Featuring A Double-Cage Structure

Three homometallic high-nuclearity clusters, formulated as [(CO3)2@Ln37(LH3)8(CH3COO)21(CO3)12(μ3-OH)41(μ2-H2O)5(H2O)40]·(ClO4)21·(H2O)100 (abbreviated as Ln37, Ln = Gd (1); Tb (2); Eu (3), LH3 = 1,2,3-cyclohexanetriol) and featuring a double cage-like structure, were obtained through the reaction of 1,2,3-cyclohexanetriol, acetate ligand, and Ln(ClO4)3. The largest odd-numbered lanthanide cluster Gd37 exhibits an entropy change (-ΔSm) of 38.7 J kg-1 K-1.

A Gigantic Molecular Wheel of {Gd140}: A New Member of the Molecular Wheel Family

Nanoscale inorganic wheel-shaped structures are one of the most striking types of molecular aggregations. Here, we report the synthesis of a gigantic lanthanide wheel cluster containing 140 Gd3+ atoms. As the largest lanthanide cluster reported thus far, {Gd140} features an attractive wheel-like structure with 10-fold symmetry. The nanoscopic molecular wheel possesses the largest diameter of 6.0 nm and displays high stability in solution, which allows direct visualization by scanning transmission electron microscopy. The newly discovered lanthanide {Gd140} cluster represents a new member of the molecular wheel family.

Insights into Magnetic Interactions in a Monodisperse Gd12Fe14 Metal Cluster

The largest Ln-Fe metal cluster [Gd12 Fe14 (μ3 -OH)12 (μ4 -OH)6 (μ4 -O)12 (TEOA)6 (CH3 COO)16 (H2 O)8 ]⋅(CH3 COO)2 (CH3 CN)2 ⋅(H2 O)20 (1) and the core-shell monodisperse metal cluster of 1 a@SiO2 (1 a=[Gd12 Fe14 (μ3 -OH)12 (μ4 -OH)6 (μ4 -O)12 (TEOA)6 (CH3 COO)16 (H2 O)8 ]2+ ) were prepared. Experimental and theoretical studies on the magnetic properties of 1 and 1 a@SiO2 reveal that encapsulation of one cluster into one silica nanosphere not only effectively decreases intermolecular magnetic interactions but also significantly increases the zero-field splitting effect of the outer layer Fe3+ ions.

Anion-controlled assembly of a series of heterometallic 3d–4f compounds with 0D cluster, 1D chain, 2D network and 3D frameworks

A series of heterometallic 3d–4f compounds, formulated as [Ln2Ni2(dcta)2(H2O)8(NO3)2]·8H2O (Ln = Nd (1); Ln = Dy (2)); {[DyNi(dcta)(H2O)6]·Cl·(H2O)2}n (3); {[LnNi(dcta)(H2O)6]·(ClO4)·(H2O)3}n (Ln = La (4); Ln = Nd (5)); {[Gd12Ni12(dcta)12(H2O)24]·[Ni(H2O)6]3·(ClO4)18·(H2O)80}n (6) and {[La12Ni12(dcta)12(H2O)60]·[Ni(H2O)6]3·(ClO4)18·(H2O)30}n (7), (H4dcta = trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid), have been obtained through a metalloligand strategy. Structural analysis reveals that [Ni(dcta)]2− acts as a bidentate metalloligand in 1–3, tridentate metalloligand in 4 and 5, and tetradentate metalloligand in 6 and 7. These compounds can be divided into four types according to the dimensionality of the structures. Compounds 1 and 2 are 0D tetranuclear clusters comprised of symmetric [LnNi(dcta)]2 12-membered rings, compound 3 is a 1D chain which is reinforced by hydrogen bonds. Compounds 4 and 5 possess an infinite 2D layer structure with a 63-hcb topology, and compounds 6 and 7 are two 3D frameworks constructed by face-sharing Keplerate-type metal–organic polyhedra. It is interesting that different anions lead to different topology structures. The magnetic properties and thermal stabilities of them are also studied.

Anion-Dependent Assembly of Heterometallic 3d–4f Clusters Based on a Lacunary Polyoxometalate

A series of heterometallic 3d-4f clusters, formulated as Na17[Ln3(H2O)5NiII(H2O)3(Sb4O4)(SbW9O33)3(NiIIW6O24)(WO2)3(CH3COO)]·(H2O)65 [abbreviated as Ln3Ni2, where Ln = La3+ (1), Pr3+ (2), and Nd3+ (3)], K5Na11[Ln3(H2O)3NiII3(H2O)6(SbW9O33)3(WO4)(CO3)]·(H2O)40 [abbreviated as Ln3Ni3, where Ln = La3+ (4), Pr3+ (5), and Nd3+ (6)], and K3Na27[Ln3NiII9(μ3-OH)9(SbW9O33)2(PW9O34)3(CH3COO)3]·(H2O)80 [abbreviated as Ln3Ni9, where Ln = Dy3+ (7) and Er3+ (8)], were obtained through the reaction of the lacunary {SbW9O33} precursor with Ln(NO3)3·6H2O and NiCl2·6H2O in a NaAc/HAc buffer in the presence of different anions. Single-crystal X-ray structure analysis revealed that compounds 1-3 possessed tetrameric architectures featuring three Keggin-type {SbW9O33} and one Anderson-type {NiIIW6O24} building blocks encapsulating one {Sb4O4} cluster, three WO2 units, three Ln3+ metal ions, and two Ni2+ metal ions. Compounds 4-6 displayed cyclic trimeric aggregates of three {SbW9O33} units enveloping one CO32--templated trinuclear [Ln3(CO3)]7+ and one WO42--templated [NiII3(WO4)]+ unit. Compounds 7 and 8 exhibited unique pentameric architectures that featured three 3d-4f cubane clusters of {LnNi3(μ3-OH)3} capped by two {SbW9O33} and three {PW9O34} building blocks. Interestingly, the structural regulation of the heterometallic 3d-4f clusters in the polyoxometalate systems with trimers, tetramers, and pentamers was realized by introducing different anions.

Synthesis and Structures of Lanthanide–Transition Metal Clusters

Based on the inherent contribution of the d–f electrons and the unique exchange interactions between different metal ions, heterometallic lanthanide–transition metal (d–f) clusters have received substantial attention in modern chemistry. In the past two decades, numerous lanthanide–transition metal clusters with diverse molecular structures have been obtained. Various synthetic approaches have been developed by analyzing the crystal structures and reaction conditions. In this chapter, we discussed synthetic methodology based on hard and soft acids and bases (HSAB) theory and the resulting structures. In addition, personal perspectives and outlooks regarding the future research directions of d–f molecular clusters are provided at the end of this chapter.

Four 3d–4f heterometallic Ln45M7 clusters protected by mixed ligands

Four high-nuclearity lanthanide–transition metal clusters, formulated as [Ln45M7(OH)68(CO3)12(CH3COO)26(CH3CH2COO)6(H2O)70]·(ClO4)25·(H2O)x (abbreviated as Ln45M7: 1, Gd45Co7; 2, Gd45Ni7; 3, Dy45Co7; 4, Dy45Ni7; x ≈ 50), were obtained with the mixed protecting ligands acetate and propionate. Structural analysis shows that the cluster cationic core contains 52 metal ions featuring a bowl-like structure. 12 CO32− and 3 ClO4− anions play the role of mixed anion templates. Magnetic studies reveal that the two isotropic Gd-containing clusters Gd45Co7 and Gd45Ni7 exhibit a large magnetocaloric effect (MCE), while the anisotropic Dy-containing clusters Dy45Co7 and Dy45Ni7 show slow relaxation of magnetization.