Lanthanide Clusters Research Articles

Photochromic Polyoxoniobates with Photoinduced "D-f-A" Electron Transfer Mechanism.

Compounds with redox activities have appealing applications in catalytic, electronic and magnetic properties, but the redox inert of polyoxoniobates (PONbs) significantly limits their applications for a long time. In this work, we are able to integrate organophosphate and lanthanide cluster into PONb to create the first family of inorganic-organic hybrid organophosphate-Ln-PONb composite clusters. These novel species not only present the first family of redox active PONbs that can be reduced to form long-lived "heteropoly blues" under ambient conditions, but also a new photochromic system. More importantly, the analyses of the electronic configurations and photochromic properties for a series of designed proof-of-concept PONbs models allow us to discover a D-f-A electron transfer mechanism, that is, photoinduced electron is transferred from a photosensitive organophosphate electron donor (D) to the NbV electron acceptor (A) through the unoccupied 4f-orbitals of Ln (f). This work paves the way for developing diverse PONb-based redox materials and expanding the possibility of the applications of PONbs in the redox chemistry.

Visual and Real-Time Monitoring of Cd2+ in Water, Rice, and Rice Soil with Test Paper Based on [2 + 2] Lanthanide Clusters

Cadmium ions (Cd2+) are highly toxic to animal and human health, especially through the drinking of Cd2+-contaminated water and eating Cd2+-contaminated rice. Therefore, accurate detection of Cd2+ in water, rice, and rice soil is urgent. In this work, two [2 + 2] lanthanide clusters of Tb2Tb2 and Eu2Eu2 were synthesized and characterized in detail. Interestingly, Tb2Tb2 is a rapid sensor for Cd2+ through luminescence "turn-off". Further studies show that Tb2Tb2 is a highly sensitive and selective sensor toward Cd2+ in water, rice supernatants, and rice soil supernatants, with a very short response time of 20 s. The limit of detection (LOD) in the above three real samples is as low as 0.0112, 1.1240, and 0.1124 ppb, respectively, which is lower than the national standards for food safety in China (GB 2762-2022). More interestingly, a portable sensing device of test paper based on Tb2Tb2 is developed with a facile method, which shows visible, highly sensitive, and selective sensing toward Cd2+ in real samples of water, rice supernatants, and rice soil supernatants. Tb2Tb2 and its sensing device of test paper are an on-site analysis sensor for potentially non-expert users, especially for people in remote rural areas.

High-stability spherical lanthanide nanoclusters for magnetic resonance imaging.

High-nuclear lanthanide clusters have shown great potential for the administration of high-dose mononuclear gadolinium chelates in magnetic resonance imaging (MRI). The development of high-nuclear lanthanide clusters with excellent solubility and high stability in water or solution has been challenging and is very important for expanding the performance of MRI. We used N-methylbenzimidazole-2-methanol (HL) and LnCl3·6H2O to synthesize two spherical lanthanide clusters, Ln32 (Ln = Ho, Ho32; and Ln = Gd, Gd32), which are highly stable in solution. The 24 ligands L- are all distributed on the periphery of Ln32 and tightly wrap the cluster core, ensuring that the cluster is stable. Notably, Ho32 can remain highly stable when bombarded with different ion source energies in HRESI-MS or immersed in an aqueous solution of different pH values for 24 h. The possible formation mechanism of Ho32 was proposed to be Ho(III), (L)- and H2O → Ho3(L)3/Ho3(L)4 → Ho4(L)4/Ho4(L)5 → Ho6(L)6/Ho6(L)7 → Ho16(L)19 → Ho28(L)15 → Ho32(L)24/Ho32(L)21/Ho32(L)23. To the best of our knowledge, this is the first study of the assembly mechanism of spherical high-nuclear lanthanide clusters. Spherical cluster Gd32, a form of highly aggregated Gd(III), exhibits a high longitudinal relaxation rate (1 T, r1 = 265.87 mM-1·s-1). More notably, compared with the clinically used commercial material Gd-DTPA, Gd32 has a clearer and higher-contrast T1-weighted MRI effect in mice bearing 4T1 tumors. This is the first time that high-nuclear lanthanide clusters with high water stability have been utilized for MRI. High-nuclear Gd clusters containing highly aggregated Gd(III) at the molecular level have higher imaging contrast than traditional Gd chelates; thus, using large doses of traditional gadolinium contrast agents can be avoided.

Doping transition metals to modulate the chirality and photocatalytic activity of rare earth clusters.

In this paper, we report the successful assembly of achiral {Ln6M} ([Ln6M(μ3-OH)8(acac)12(CH3O)x(CH3OH)y], Ln = La, M = Mn, Co, Fe) and chiral {Nd9Fe2} ([Nd9Fe2(μ4-O)(μ3-OH)14(acac)16(NO3)(CH3OH)2(H2O)3]) rare earth clusters using achiral rigid ligands and a transition metal doping strategy. {Ln6M} can be viewed as the fusion of two {Ln3M} tetrahedrons by sharing vertices. {Nd9Fe2} results from the fusion of four {Ln3M} tetrahedrons by vertice and edge sharing. The substitution of Ln with transition metal leads to changes in the coordination pattern around neighboring Ln, which triggers the switch of metal center chirality. This study demonstrates the potentiality of utilizing transition metal doping and rigid ligand to control the chirality of rare earth clusters. In addition, the photocatalytic CO2 activity of these transition metal-doped rare earth clusters has been studied.

Octahedral lanthanide clusters containing a central PO43- anion: structural, luminescent, magnetic and relaxometric properties.

Lanthanide clusters with good stability and intriguing physical properties are attractive in many fields. By reacting 9-anthracenylphosphonic acid (AnPO3H2) and lanthanide nitrates under solvothermal conditions, we obtained a series of hexanuclear lanthanide phosphonate cages [H3O][Ln6(PO4)(AnPO3)8(DMF)6]·2DMF·H2O (Ln6, Ln = NdIII, EuIII, GdIII, DyIII, HoIII, ErIII, YbIII). Within the cluster, the six Ln atoms form an octahedron and its eight faces are covered by phosphonate groups. The in situ generated phosphate anion resides inside the cage and binds to the six Ln atoms via its four oxygen atoms. Photoluminescence studies show that Nd6, Er6 and Yb6 can emit near-infrared (NIR) luminescence due to the energy transfer from the anthracene ligand to the lanthanide ions. Magnetic studies reveal the magnetocaloric effect of Gd6 with an entropy change (-ΔSm) of 25.92 J kg-1 K-1 at 2.5 K and ΔH = 0-7 T. The possibility of using Gd6 as a contrast agent for magnetic resonance imaging was also explored with longitudinal (r1) and transverse (r2) relaxivities of 5.68 mM-1 s-1 per Gd and 158.11 mM-1 s-1 per Gd, respectively.

Highly stable drone-shaped lanthanide clusters: structure, assembly mechanism, and crystalline–amorphous transitions

We have synthesized a drone-shaped lanthanide cluster 1, and its possible self-assembly mechanism was speculated. We observed the transition from crystalline to amorphous high-nuclear lanthanide clusters for the first time.

MoO42--templated Ln20Ni21 heterometallic clusters with large low-field magnetic entropy.

The anionic template method is an effective strategy for synthesizing high-nuclearity transition-lanthanide (3d-4f) heterometallic clusters. Herein, two lanthanide clusters with formulas [Gd20Ni21(μ3-OH)21(CO3)6(IDA)21(C2H4NO2)6(C2O4)3(MoO4)1.5(μ2-OH)1.5(H2O)9]Cl10.5·79H2O (1) and [Tb20Ni21(μ3-OH)21(CO3)6(IDA)21(C2H4NO2)6(C2O4)3(MoO4)(μ2-OH)2(H2O)10]Cl11·32H2O (2) were synthesized by introducing MoO42- anions as templates. Structural analysis indicates that compounds 1 and 2 are isomorphic, featuring a fascinating triangular-shaped metal framework. Magnetic property investigations illuminate the fact that compound 1 exhibits a large -ΔSm of 37.83 J kg-1 K-1 at 3 K for ΔH = 7 T. In particular, it is worth mentioning that compound 1 has an excellent low-field magnetic entropy (-ΔSm = 23.85 J kg-1 K-1 at 2 K, 2 T).

Highly stable and differentially arranged hexanuclear lanthanide clusters: structure, assembly mechanism, and magnetic resonance imaging

This study employs diacylhydrazone-derived ligands to realize controllable construction of differentiated hexanuclear lanthanide clusters with identical cores but different template-motif arrangements for the first time.

The Assembly of Grid-type Lanthanide Cluster

A dicompartmental Schiff base ligand was synthesized and used for the assembly of a lanthanide grid-like complex. Dinuclear Dy2 and tetranuclear Dy4 complexes were isolated from the reaction of the ligand with different dysprosium salt. Single crystal X-ray diffractions show that the two DyIII ions in Dy2 are adopted in the N3O coordination pockets of the ligand and further coordinated by water molecules, whereas, for Dy4, the four DyIII ions are clamped by four ligands through their terminal N3O coordination pockets, forming a grid-type assembly. Magnetic studies reveal that complex Dy2 shows field-induced single-molecule magnetic behavior under 1000 Oe dc field, complex Dy4 shows fast relaxation under zero field and field-induced single-molecule magnet (SMM) behavior under 500 Oe. The difference in the magnetic relaxation is related to the various deprotonation of the ligand and distinct topology of the assemblies.

Thiacalix[4]arene-Sandwiched Sandglass-like Ln9 Clusters (Ln = Tb and Eu): Insights into the Selective Luminescence Quenching Properties by p-Nitrobenzene Derivatives

Nonanuclear lanthanide clusters Ln9 (Ln = Tb and Eu) based on p-tert-butylthiacalix[4]arene (H4TC4A) have been synthesized by the solvothermal reaction and were structurally determined by single-crystal X-ray diffraction. The framework of Ln9 can be termed as a sandglass-like structure whose two Ln4-TC4A polynuclear secondary building units are bridged by one octa-coordinate {Ln(μ3-O)8} unit. Efficient TC4A-to-Ln energy transfer was observed for Tb9 but not for Eu9. The luminescence quantum yield (QY) of Tb9 in the solid state at room temperature was determined to be 17.6%, while its highest QY in a methanolic solution (2 × 10-5 mol/L) is 59.2% upon excitation at 318 nm. The luminescence of Tb9 was quenched selectively by derivatives of p-nitrobenzene, as demonstrated by the results of photoluminescence and UV-vis titration experiments and supported by density functional theory calculations. We believe that the interactions between the analyte molecules and the pocket of Tb9 are primarily responsible for the observed quenching. As such, this work represents one of the few examples of utilizing structurally interesting lanthanide cluster complexes as a sensory platform for the recognition of meaningful analytes and portends the further development of lanthanide-calixarene-complex-based functional materials.

In situ synthesized homochiral dysprosium-oxo clusters with threonine Schiff bases

Chiral high-nuclearity lanthanide (4f) clusters have shown fantastic properties in various fields. However, their synthesis is still of great challenge. Herein, we report two pairs of enantiomers of high-nuclearity Dy-oxo clusters synthesized through in situ strategy. They are [Dy18(R/SHftp)4 (R/SH2btp)4(μ2-OH)8(μ3-OH)20(μ6-O)(NO3)4(μ-H2O)8]·[solvents] (1R and 1S) and [Dy9(R/SHftp)2 (R/SH2btp)2(OAc)6(μ3-OH)10(H2O)6](OAc)·[solvents] (2R and 2S), where R/SHftp2− and R/SH2btp3− represent in situ formed 2-formyl-6-[N-(threonine)iminomethyl]-4-methylphenol and 2,6-bis[N-(threonine)iminomethyl]-4-methylphenol anions, respectively. These in situ formed clusters were endowed with not only homochirality via introducing R/SHftp2− and R/SH2btp3− ligands, but also rich oxo-bridges by controlling the hydrolysis of DyIII ions. Different anions from DyIII salts further induced structural variation between two sets of clusters. 1R and 1S feature an unprecedent four-blade propeller shaped {Dy18} core, whose centered octahedral {Dy6} unit are surrounded by four triangular {Dy3} units. Strikingly, they represent the second largest chiral 4f cluster species so far. 2R and 2S display a sandglass-like {Dy9} skeleton that consist of two square pyramid {Dy5} units sharing a DyIII vertex. Magnetic investigation revealed possible antiferromagnetic interactions between the DyIII centers in these clusters.

Anion-Manipulated Hydrolysis Process Assembles of Giant High-Nucleation Lanthanide-Oxo Cluster.

Widespread concern has been raised over the synthesis of highly nucleated lanthanide clusters with special shapes and/or specific linkages. Construction of lanthanide clusters with specific shapes and/or linkages can be achieved by carefully regulating the hydrolysis of lanthanide metal ions and the resulting hydrolysis products. However, studies on the manipulation of lanthanide-ion hydrolysis to obtain giant lanthanide-oxo clusters have been few. In this study, we obtained a tetraicosa lanthanide cluster (3) by manipulating the hydrolysis of Dy(III) ions using an anion (OAc-). As far as we know, cluster 3 has the highest nucleation among all lanthanide-oxo clusters reported. In 3, two triangular Dy3O4 are oriented in opposite directions to form the central connecting axis Dy6(OH)8, which is in turn connected to six Dy3O4 that are oriented in different directions. Meanwhile, a sample of a chiral trinuclear dysprosium cluster (1) was obtained in a mixed CH3OH and CH3CN solvent and by replacing the anion in the reaction to Cl- ions. In this cluster, 1,3,4-thiadiazole-2,5-diamine (L2) is free on one side through π···π interactions and is parallel to the o-vanillin (L1)- ligand, thus resulting in a triangular arrangement. The arrangement of L2 affects the end group coordination in the cluster 1 structure through hydrogen bonding and induces the cluster to exhibit chirality. When the reaction solvent was changed to CH3OH, a sample of cluster 2, composed of two independent triangular Dy3 that have different end group arrangements, was obtained. Magnetic analysis showed that clusters 1 and 3 both exhibit distinctive single-molecule magnetic properties under zero-magnetic-field conditions. This study thus provides a method for the creation of chiral high-nucleation clusters from achiral ligands and potentially paves the way for the synthesis of high-nucleation lanthanide clusters with unique forms.

Detection of heavy metal ion in real samples with fiber based paper based on new rare earth cluster

Chromium (Cr) is an important material, but also one of the most toxic heavy metal pollutants, showing great threat to human health and ecological environment, thus, accurate and rapid detection of Cr3+ has far-reaching significance. In this work, based on the ligand of 2,3,4,5,6-pentafluorobenzoic acid (HPFBA) that does not contains oscillation effect group such as “CH, OH, and NH bond”, three rare earth dinuclear cluster of Ln2(PFBA)6(phen)2(H2O)2 (Ln = Tb3+1-Tb, Eu3+1-Eu, Gd3+1-Gd, phen = 1,10-phenanthroline) were obtained. 1-Tb shows excellent stability and luminescence properties. In depth investigation reveals that 1-Tb shows quick detection towards Cr3+ in water through luminescence “turn-off”, with extremely short response time of 1.0 min, very low limit of detection (LOD) of 5.2 ppb and no interference from other ions. The LOD value is much lower than the total content of chromium for water in China (15 ppm, GB9078-1996). In the actual environment such as tap water, lake water, human, and serum, 1-Tb shows excellent detection and recovery rate for Cr3+. More interestingly, a fiber based paper of test paper that based on 1-Tb and ordinary filter paper was fabricated, which can probe Cr3+ by visible color changes to the naked eye under UV light.

Reticular chemistry for the rational design of mechanically robust mesoporous merged-net metal-organic frameworks

Reticular chemistry for the rational design of mechanically robust mesoporous merged-net metal-organic frameworks

Alkali metal-linked triangular building blocks assemble a high-nucleation lanthanoid cluster based on single-molecule magnets

SummaryThe metallic central magnetic axes in high-nucleation clusters with complex structural connections tend to be disorganized and cancel each other out. Therefore, high-nucleation clusters cannot easily exhibit single-molecule magnets (SMMs) behaviors. Herein, we select a triple-core building block (Dy3K2, 1) and use linked diamagnetic alkali metal to form an open, spherical, high-nucleation cluster Dy12Na6 (3) with SMM behavior. Furthermore, by changing the reaction conditions, Dy6K2 (2) formed by linking two Dy3 by K(I) is obtained. High-resolution electrospray mass spectrometry of clusters 1–3 effectively captures the building block Dy3, and clusters 1 and 3 and Dy3 have high stability even with the increase in ion source energy. To the best of our knowledge, this is the first time that an SMM based on a high-nucleation cluster has been obtained by connecting magnetic primitives via diamagnetic metal ions. Dy12K6 is currently the highest nuclear ns-4f heterometallic SMM.

New wheel-shaped Ln6 clusters for conversion of CO2 and magnetic properties

A series of novel hexanuclear lanthanide clusters, namely, [Ln6(HL)6(NO3)6]·3CH3CN (Ln = Gd(1), Tb(2), Dy(3) and Er(4)) was assembled using a multidentate ligand H3L (trolamine). The clusters 1–4 show a wheel-shaped Ln6 topology with the approximate diameter and thickness of 1.5 and 0.7 nm, respectively. All of them show high thermal stability. In the aspect of the catalytic capacities for the cycloaddition reactions of CO2 and epoxide, the reaction conditions, the substrate scope, and possible catalytic mechanism were investigated. The highest yield for clusters 1–4 is up to 99% at 333 K for 12 h. In particular, cluster 1 can be reused at least three times with no obvious loss of catalytic performance and keep the integrity of the crystal structure. Magnetic investigations reveal that cluster 1 exhibits a relatively large magnetocaloric effect with −ΔSm = 41.43 J/(kg⋅K) (T = 3.0 K, 7.0 T); while cluster 3 displays slow magnetic relaxation behavior under zero dc field with Ueff = 0.51 K and τ0 = 2.54 × 10−5 s.

Mixed-lanthanide clusters: A bridging approach that permits the design of molecular magnetic materials by introducing heavy lanthanides into the 3d-light lanthanide clusters without breaking structural integrity

Theoretical studies suggest that the ring 3d-4f clusters {MnIII4Ln4} may be a good material for magnetic refrigeration. However, only {MnIII4Ln4} constructed from light lanthanide ions have been obtained, while the attempt for their analogue containing the magnetically isotropic Gd(III) ions has failed. By applying the strategy of synthesizing mixed-lanthanide clusters, mixed-lanthanide clusters {MnIII4LaxGd4-x} and {MnIII4NdxGd4-x} without breaking structural integrity of {MnIII4Ln4} have been successfully made. It is found that smaller ionic radius difference between the lanthanides tends to increase the introduction of Gd(III) when applying the strategy. Moreover, the magnetic property measurements show that the obtained mixed-lanthanide clusters exhibit magnetothermal effect as predicted.

Ultrastable Photoluminescence Enabled by 1D Rare-Earth Metal-Organic Frameworks Based on Double Thiacalix[4]arene-Capped Nodes.

Luminescent stability is a vital factor that dictates the application of lanthanide luminescent materials. Designing luminescent lanthanide cluster nodes that form an extended framework with predictable linking patterns may help enhance the structural stability of the lanthanide complexes and hence lead to improved luminescent stability. Herein, we report a series of one-dimensional (1D) rare-earth metal-organic framework compounds, {Ln4(μ4-OH)(TC4A)2(H2O)2(CH3O)(HCOO)2(HCOOH)}·xCH3OH (Ln = Sm (1), Eu (2), Tb (3), Dy (4); x = 1-5), based on double thiacalix[4]arene-capped Ln4(μ4-OH)(TC4A)2 nodes. The axially capped Ln4(μ4-OH)(TC4A)2 nodes are connected equatorially by formate bridges to form zigzag 1D-metal-organic framework (MOF) chains, which further assemble into a quasi-two-dimensional (2D) structure via hydrogen bonding. These unique features result in a stable structure and therefore superior luminescent stability. For example, the Tb-based 1D-MOF (3) exhibits intensive green photoluminescence with a quantum yield of 53% and an average decay time of 1.33 × 106 ns. It maintains its integrated emission intensity at 96.5, 94.5, and 89.4% of the original value after being exposed to moisture (soaking in water for 10 days), elevated temperature (150 °C), and UV (15 days of continuous radiation), respectively, demonstrating excellent luminescent stability. We adopt the Tb-based 1D-MOF (3) as the green phosphor and successfully fabricate a prototype white-light-emitting diode (LED) with stable emission under long-term operation. Our synthetic strategy allows control over the linking pattern of lanthanide nodes, providing a predictive route to obtain lanthanide MOFs with improved luminescent stability.

Sm cluster on hexagonal boron nitride supported by Ir(111): Formation of magnetic cluster superlattice Sm13[formula omitted]h-BN[formula omitted]Ir(111)

The goal toward the ultimate density limit of magnetic information storage is now focused on the creations of identical magnetic clusters as well as their arrangements on a template surface for obtaining an equidistant, monodisperse and equally oriented pattern. To achieve this goal, the combination of rare-earth (RE) cluster and specific template is a viable route, e.g., h-BN monolayer on Ir(111) surface within a corrugated moiré structure (h-BN|Ir(111)) can act as a promising template to steer the intrinsically magnetic RE cluster in a well-defined orientation. Combining abinito molecular dynamic (AIMD) simulation and spin–orbital coupling density function theory (DFT) calculations, we report that magnetic Sm13 cluster can be stably deposited at the pore region of h-BN|Ir(111) template. The low-lying moiré region potential of h-BN|Ir(111) template, stable icosahedron structure of Sm13 cluster, and strong hybridization of Sm-5d6s orbitals with B/N-sp orbitals, play the synergetically roles to form Sm13@h-BN|Ir(111) cluster superlattice. The local magnetic moments of Sm atoms in Sm13 cluster are found to be robust against the structural configuration, localized site and inter-atom magnetic coupling, because their highly localized 4f states hybridize less with the spd states. Nevertheless, different deposition orientations and consequently the altered bonding interactions between Sm atoms and h-BN monolayer lead to different magnetic orders among Sm atoms. The appearances of large magnetic moment and giant magnetic anisotropy energy (MAE) of Sm13 cluster as well as its high deposition stability render Sm13@h-BN|Ir(111) for potential application of magnetic storage.

Inside Cover: Anion‐Guided Stepwise Assembly of High‐Nuclearity Lanthanide Hydroxide Clusters (Angew. Chem. Int. Ed. 33/2022)

The rational synthesis of high-nuclearity lanthanide cluster remains challenging. In their Research Article (DOI: 10.1002/anie.202205385), Min Feng, Zhiping Zheng et al. developed a stepwise synthesis of a high-nuclearity sodalite cage-like cluster Er60, guided by judiciously selected anions. The successive introduction of I−, CO32−, and NO3− led to the isolation of three crucial intermediate clusters, namely the wheel-like Er12, ship-like Er34, and bowl-like Er48. The findings opened the “black box” of the elusive self-assembly process and provided mechanistic insights.