Lanthanide-containing clusters for catalytic water splitting and CO2 conversion

Electrospray Ionization Mass Spectrometry Insights into the Assembly of Lanthanide-Containing Clusters

ConspectusAtomically precise metal clusters with well-defined crystal structures have emerged as a rapidly growing field within coordination and materials chemistry. Among them, lanthanide-containing clusters (LCCs) are particularly notable for their aesthetically pleasing architectures and intriguing properties. Achieving precise synthesis and accurate structural characterization of these clusters is crucial for unlocking their potential applications. Mass spectrometry (MS), particularly electrospray ionization mass spectrometry (ESI-MS), has proven to be a powerful tool, providing exceptional sensitivity and clarity in revealing the formation mechanisms and structural details of metal clusters. In this Account, we explore the synthesis, characterization, and assembly mechanisms of LCCs utilizing ESI-MS. We begin by tracing the historical development of LCCs, emphasizing the critical role of single-crystal X-ray diffraction in structural confirmation and the challenges associated with it. We then discuss the application of ESI-MS in characterizing LCCs, highlighting how this technique can monitor the formation processes of LCCs and determine their molecular weights and charge states. We introduce the mass difference fingerprint of isomorphism (MDFI) method, which can facilitate rapid analysis of LCCs' mass spectrometry data. Furthermore, we discuss the state of LCCs in solution and the challenges in their characterization. By utilizing ESI-MS, we enhance the understanding of the assembly mechanisms of LCCs and propose new strategies for designing and synthesizing new LCCs with tailored structures and functions. Looking forward, the ESI-MS method will play increasingly significant roles in LCC research. The continued development of these technologies will deepen the understanding of the structure-property relationships. With the ongoing convergence of computational chemistry and information science, we anticipate more precise design and synthesis of LCCs, leading to broader applications in magnetism, optics, and catalysis.

Porous 3 d-4 f Coordination Clusters for Selective Visible-Light Photocatalytic CO2 Reduction to CO

We report herein two families of porous coordination clusters (PCCs) with 216 nuclearity (M120RE96 or PCC-216MR) and 300 nuclearity (Co144Gd156 or PCC-300CG). For the first family M could be either nickel or cobalt, and RE = Pr, Nd, Sm, Eu, and Gd; while the latter features the highest nuclearity of transition-rare earth metal clusters. Characterized by their cube-like, hollow structures, these clusters exhibit the ability to absorb N2 and CO2. Besides, these clusters can be dissolved in both aqueous and acetonitrile/methanol solutions, and capable of acting as homogeneous catalysts for converting CO2 to CO under visible light. The gadolinium analogues of these clusters all show turnover numbers over 10000 and turnover frequencies over 1 s-1. In particular, the nickel based bimetallic cluster (PCC-216NG) demonstrates nearly 100 % selectivity for the reduction product, which may open a new direction for the design and development of PCCs based catalysts.

A Hollowed-Out Heterometallic Cluster for Catalytic Knoevenagel Condensation

Lanthanide-containing clusters are synthetically challenging and with significant chemical and materials applications. Herein, two isostructural heterometallic clusters of the formula (NO3)12@[Ln132Ni78(OH)292(IDA)48(CH3COO)96(NO3)12(H2O)78]Cl44⋅xH2O⋅yCH3OH (IDA=iminodiacetate; Ln=Gd 1, x=110, y=0; Ln=Eu 2, x=95, y=40) were obtained via co-hydrolysis of Ln3+ (Gd3+ or Eu3+) and Ni2+ in the presence of iminodiacetate (IDA). Crystallographic studies show that each features a truncated tetrahedral core of Ln132Ni78 within which a void of 1.1 nm in diameter; connecting the central cage and its exterior are four trumpet-like passageways surface-decorated with dinuclear units of [Gd(μ3-OH)2Gd]. Mass spectroscopic analyses indicate that both clusters maintained their structural integrity in aqueous solution, with cryo-electron microscopy providing the most convincing visual evidence in support of the cluster's solution stability. Size-selective Knoevenagel condensation, believed to occur in the passageways on the basis of experimental and molecular modeling results, was achieved in the presence of 1. The application of 1 as a uniquely structured molecular reactor and a recyclable heterogeneous catalyst was further illustrated by the one-pot three-component synthesis of biologically and pharmaceutically significant 4H-pyran derivatives.

Anion-Guided Hierarchical Assembly of Heterometallic Clusters

Anions are important as templates for the construction of many structurally sophisticated and functional supramolecular architectures. Deciphering the specific role of such templates remains a great challenge due to the unique characteristics of anions. Herein, three heterometallic Ce-Ni clusters, namely, [Ce24Ni36L36(μ4-OAc)6(OH)52(Cl)8]Cl6·110H2O (Ce24Ni36, OAc = acetate ion, L = N-methyliminodiacetate), [Ce17Ni27L27(μ6-C2O4)6(OH)15(Cl)16(H2O)19](ClO4)2Cl6·45H2O (Ce17Ni27), and [Ce21Ni30L30(μ6-C2O4)2(μ4-OAc)(OH)32(Cl)15(H2O)14](ClO4)4Cl7·55H2O (Ce21Ni30), were obtained and structurally characterized; the formation of these cage-like clusters was assisted, respectively, by acetate, oxalate, and a combination of the two as templates. Structural analyses generate key information on the anion-directed hierarchical assembly, starting from a primary building block of {CeNi3} to two anion-specific secondary building blocks (SBUs)─the tetragonal {Ce4Ni8(OAc)} and the pentagonal {Ce5Ni9(C2O4)}. Further assembly steps are guided by these curved SBUs, affording a truncated octahedral Ce24Ni36 and a lantern-like Ce17Ni27, with acetate and oxalate being the sole template, respectively. The combined use of acetate and oxalate produced Ce21Ni30, a cluster with an unprecedented structure viewable as a hybrid of a truncated octahedron and a dodecahedron.

Assembling Giant Nanoclusters as Heterogeneous Catalysts for Effectively Converting CO2 to CO Under Visible Light

Heterometallic lanthanide-transition metal (3d-4f) nanoclusters with well-defined structures and multiple active sites are excellent vehicles for achieving efficient catalysis and studying heterometallic synergism. In this work, two closely related yet different high-nuclearity nanoclusters, 72-nuclear {Ni28RE44} (1, RE = Pr, Nd, Sm, Eu, and Gd) and 111-nuclear {Ni48La63} (2), are synthesized using a mixed-ligand strategy. Importantly, the crystal solids of these giant coordination clusters are insoluble when soaking in H2O/CH3CN and can be used as heterogeneous catalysts for visible-light-driven catalytic conversion of CO2 to CO. Cluster 2 exhibits a maximum CO production rate of 4800 µmol g-1 h-1 and a CO selectivity of 92% over H2. Furthermore, the catalytic properties are investigated of different rare earths in the cluster 1 series, found that 1-Eu exhibited superior catalytic performance under identical conditions, likely due to the lower reduction potential of the europium ions. This study represents the first report of 3d-4f heterometallic nanoclusters as heterogeneous catalysts for photocatalytic reaction and provides a reference for the study of high-nuclearity 3d-4f nanoclusters as catalysts for photocatalytic reduction of CO2 to CO.

Selective arrangement of three types of calcium-terbium tetranuclear cores by a thiacalixarene ligand using thermodynamic and kinetic strategies

In this study, we report thermodynamic and kinetic strategies for arranging three types of Ca-Tb heterotetranuclear cores in a square configuration sandwiched by thiacalix[4]arene-p-tetrasulfonate (TCAS) ligands in aqueous solutions. In the thermodynamic strategy, the components were mixed under optimum pH conditions to afford a complex with a desired ratio of Ca:Tb:TCAS. In the kinetic strategy, the Ca1Tb3TCAS2 complex was formed via mixing kinetically stable Tb3TCAS2 with Ca2+. Interestingly, the resulting complexes (Ca x Tb4-x TCAS2, x = 1-3) exhibited Tb-centered luminescence upon excitation of the TCAS center with a high quvdantum yield (ϕ = 0.11-0.14) and a long luminescence lifetime (approximately 1.2 ms). The thermodynamic strategy can be applied to Sr2+ instead of Ca2+, but it is not suitable for first transition metal ions. However, the kinetic strategy is versatile and can be applied to first transition metal ions to afford M1Tb3TCAS2 (M = Sr2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+).

Application of Hard and Soft Acid-base Theory to Construct Heterometallic Materials with Metal-oxo Clusters

Heterometallic cluster-based materials offer the potential to incorporate multiple functionalities, leveraging the aggregation effects of clusters and translating this heterogeneity and complexity into unexpected properties that are more than just the sum of their components. However, the rational construction of heterometallic cluster-based materials remains challenging due to the complexity of metal cation coordination and structural unpredictability. This minireview provides insights into a general synthetic strategy based on Hard and Soft Acids and Bases (HSAB) theory, summarizing its advantages in the designed synthesis of discrete heterometallic clusters (intracluster assembly) and infinite heterometallic cluster-based materials (intercluster assembly). Furthermore, it emphasizes the potential to exploit the intrinsic properties of mixed components to achieve breakthroughs across a broad range of applications. The insights from this review are expected to drive the progress of heterometallic cluster-based materials in a controllable and predictable manner.

Advanced EXAFS analysis techniques applied to the L-edges of the lanthanide oxides

The unique properties of the lanthanide (Ln) elements make them critical components of modern technologies, such as lasers, anti-corrosive films and catalysts. Thus, there is significant interest in establishing structure-property relationships for Ln-containing materials to advance these technologies. Extended X-ray absorption fine structure (EXAFS) is an excellent technique for this task considering its ability to determine the average local structure around the Ln atoms for both crystalline and amorphous materials. However, the limited availability of EXAFS reference spectra of the Ln oxides and challenges in the EXAFS analysis have hindered the application of this technique to these elements. The challenges include the limited k-range available for the analysis due to the superposition of L-edges on the EXAFS, multielectron excitations (MEEs) creating erroneous peaks in the EXAFS and the presence of inequivalent absorption sites. Herein, we removed MEEs to model the local atomic environment more accurately for light Ln oxides. Further, we investigated the use of cubic and non-cubic lattice expansion to minimize the fitting parameters needed and connect the fitting parameters to physically meaningful crystal parameters. The cubic expansion reduced the number of fitting parameters but resulted in a statistically worse fit. The non-cubic expansion resulted in a similar quality fit and showed non-isotropic expansion in the crystal lattice of Nd2O3. In total, the EXAFS spectra and the fits for the entire set of Ln oxides (excluding promethium) are included. The knowledge developed here can assist in the structural determination of a wide variety of Ln compounds and can further studies on their structure-property relationships.

Phase-Stabilized Nickel-Molybdenum Electrocatalyst by Samarium Doping for Hydrogen Evolution in Alkaline Water Electrolysis

Although the nickel-molybdenum electrocatalyst exhibits excellent activity in the alkaline hydrogen evolution reaction (HER), its stability is poor mainly due to molybdenum leaching. This work reports that doping samarium into nickel-molybdenum electrocatalyst effectively suppresses molybdenum leaching by forming a stable phase consisting of Sm, Mo, and O elements. The resulting electrode displays no noticeable activity degradation during the long-term testing (> 850 h) under a current density of 500 mA cm-2 in 1 м KOH. This enhanced stability is ascribed to the formation of a robust phase within the HER potential windows in alkaline electrolytes, as evidenced by the Pourbaix diagram. Furthermore, the samarium-modified electrocatalyst exhibits increased activity, with the overpotential decreasing by ≈59 mV from 159 to 100 mV at 500 mA cm-2 compared to the unmodified counterpart. These remarkable properties stem from samarium doping, which not only facilitates the formation of a stable phase to inhibit molybdenum leaching but also adjusts the electronic properties of molybdenum to enhance water dissociation.

Synthetic Mn3Ce2O5-Cluster Mimicking the Oxygen-Evolving Center in Photosynthesis

The photosynthetic oxygen-evolving center (OEC) is a unique Mn4CaO5-cluster that catalyses water splitting into electrons, protons, and dioxygen. Precisely structural and functional mimicking of the OEC is a long-standing challenge and pressingly needed for understanding the structure-function relationship and catalytic mechanism of O-O bond formation. Herein we report two simple and robust artificial Mn3Ce2O5-complexes that display a remarkable structural similarity to the OEC in regarding of the ten-atom core (five metal ions and five oxygen bridges) and the alkyl carboxylate peripheral ligands. This Mn3Ce2O5-cluster can catalyse the water-splitting reaction on the surface of ITO electrode. These results clearly show that cerium can structurally and functionally replace both calcium and manganese in the cluster. Mass spectroscopic measurements demonstrate that the oxide bridges in the cluster are exchangeable and can be rapidly replaced by the isotopic oxygen of H2 18O in acetonitrile solution, which supports that the oxide bridge(s) may serve as the active site for the formation of O-O bond during the water-splitting reaction. These results would contribute to our understanding of the structure-reactivity relationship of both natural and artificial clusters and shed new light on the development of efficient water-splitting catalysts in artificial photosynthesis.

Unraveling the Intertwining Factors Underlying the Assembly of High-Nuclearity Heterometallic Clusters

Two closely related yet distinctly different cationic clusters, [Dy52Ni44(HEIDA)36(OH)138(OAc)24(H2O)30]10+ (1) and [Dy112Ni76(HEIDA)44(EIDA)24(IDA)4(OH)268(OAc)48(H2O)44]4+ (2) (HEIDA=N-(2-hydroxyethyl)iminodiacetate), each featuring a multi-shell core of Platonic and Archimedean polyhedra, were obtained. Depending on the specific conditions used for the co-hydrolysis of Dy3+ and Ni2+, the product can be crystallized out as one particular type of cluster or as a mixture of 1 and 2. How the reaction process was affected by the amount of hydrolysis-facilitating base and/or by the reaction temperature and duration was investigated. It has been found that a reaction at a high temperature and/or for an extended period favors the formation of the compact and thermodynamically more stable 1, while a brief reaction with a large amount of the base is good for the kinetic product 2. By tuning these intertwining conditions, the reaction can be regulated toward a particular product.

Tuning Electrocatalytic Water Oxidation Activity: Insights from the Active-Site Distance in LnCu6 Clusters

Atomically precise metal clusters serve as a unique model for unraveling the intricate mechanism of the catalytic reaction and exploring the complex relationship between structure and activity. Herein, three series of water-soluble heterometallic clusters LnCu6, abbreviated as LnCu6-AC (Ln = La, Nd, Gd, Er, Yb; HAC = acetic acid), LnCu6-IM (Ln = La and Nd; IM = Imidazole), and LnCu6-IDA (Ln = Nd; H2IDA = Iminodiacetic acid) are presented, each featuring a uniform metallic core stabilized by distinct protected ligands. Crystal structure analysis reveals a triangular prism topology formed by six Cu2+ ions around one Ln3+ ion in LnCu6, with variations in Cu···Cu distances attributed to different ligands. Electrocatalytic oxygen evolution reaction (OER) shows that these different LnCu6 clusters exhibit different OER activities with remarkable turnover frequency of 135 s-1 for NdCu6-AC, 79 s-1 for NdCu6-IM and 32 s-1 for NdCu6-IDA. Structural analysis and Density Functional Theory (DFT) calculations underscore the correlation between shorter Cu···Cu distances and improves OER catalytic activity, emphasizing the pivotal role of active-site distance in regulating electrocatalytic OER activities. These results provide valuable insights into the OER mechanism and contribute to the design of efficient homogeneous OER electrocatalysts.

Enantioselective Synthesis of Homochiral Hierarchical Nd8Fe3-Oxo Cluster from Racemic Nd9Fe2-Oxo Cluster

Enantioselective synthesis of homochiral rare earth clusters is still a great challenge. In this work, we developed an efficient "cluster to cluster" approach, that is, a pair of enantiomerical R/S-{Nd8Fe3}-oxo clusters were successfully obtained from the presynthesized racemic {Nd9Fe2}-oxo cluster. R/S-hydrobenzoin ligands trigger the transformation of the pristine clusters by an SN2-like mechanism. Compared to the pristine cluster with an achiral core, the new cluster exhibits hierarchical chirality, from ligand chirality to interface chirality, then to helix chirality, and finally to supramolecular double helix chirality. The spectral experiments monitored the transformation and confirmed distinctly structure-related optical activity. The enantiomeric pure cluster also exhibits a potential asymmetric catalytic activity.

CO2 Photoreduction over Semiconducting 2D Materials with Supported Single Atoms: Recent Progress and Challenges

In the face of the growing energy crisis and environmental challenges, substantial efforts are now directed toward sustainable clean energy as a replacement for traditional fossil fuels. CO2 photoreduction into value-added chemicals and fuels is widely recognized as a promising approach to mitigate current energy and environmental concerns. Photocatalysts comprising single atoms (SAs) supported on two-dimensional (2D) semiconducting materials (SAs-2DSemi) have emerged as a novel frontier due to the combined merits of SA catalysts and 2D materials. In this study, we review advancements in metal SAs confined on 2DSemi substrates, categorized into four groups: (1) metal oxide-based, (2) g-C3N4-based, (3) emerging, and (4) hybridized 2DSemi, for photocatalytic CO2 conversion over the past few years. With a particular focus on highlighting the distinct advantages of SAs-2DSemi, we delve into the synthesis of state-of-the-art catalysts, their catalytic performances, and mechanistic elucidation facilitated by experimental characterizations and theoretical calculations. Following this, we outline the challenges in this field and offer perspectives on harnessing the potential of SAs-2DSemi as promising photocatalysts. This comprehensive review aims to provide valuable insights for the future development of 2D photocatalytic materials involving SAs for CO2 reduction.

A Cubic Tinkertoy-like Heterometallic Cluster with a Record Magnetocaloric Effect

Clusters showing a giant magnetocaloric effect (MCE) are of interest as molecular coolants for magnetic refrigeration. Herein, we report two heterometallic clusters, denoted as Gd152Ni14@Cl24 and Sm152Ni8, just to highlight their inorganic core motifs, obtained by ligand-controlled co-hydrolysis of Ni2+ and Ln3+ (Ln = Gd, Sm) in the presence of N-(2-hydroxyethyl)iminodiacetic acid (H2HEIDA). Both clusters display fascinating cubic Tinkertoy-like structures, with the core motifs being built of multiple metallic shells of Platonic and Archimedean polyhedra. The isothermal magnetic entropy change─a direct measurement of MCE─was determined to be 52.65 J·kg-1·K-1 at 2.5 K and 7.0 T for the Gd-containing cluster; this value is the highest known for any molecular clusters so far reported.

Embedding Multiple Magnetic Components in Carbon Nanostructures via Metal-Oxo Cluster Precursor for High-Efficiency Low-/Middle-Frequency Electromagnetic Wave Absorption

With the advent of wireless technology, magnetic-carbon composites with strong electromagnetic wave (EMW) absorption capability in low-/middle-frequency range are highly desirable. However, it remains challenging for rational construction of such absorbers bearing multiple magnetic components that show uniform distribution and favorable magnetic loss. Herein, a facile metal-oxo cluster (MOC) precursor strategy is presented to produce high-efficiency magnetic carbon composites. Nanosized MOC Fe15 shelled with organic ligands is employed as a novel magnetic precursor, thus allowing in situ formation and uniform deposition of multicomponent magnetic Fe/Fe3O4@Fe3C and Fe/Fe3O4 nanoparticles on graphene oxides (GOs) and carbon nanotubes (CNTs), respectively. Owing to the good dispersity and efficient magnetic-dielectric synergy, quaternary Fe/Fe3O4@Fe3C-GO exhibits strong low-frequency absorption with RLmin of -53.5 dB at C-band and absorption bandwidth covering 3.44 GHz, while ultrahigh RLmin of -73.2 dB is achieved at X-band for ternary Fe/Fe3O4-CNT. The high performance for quaternary and ternary composites is further supported by the optimal specific EMW absorption performance (-15.7 dB mm-1 and -31.8 dB mm-1) and radar cross-section reduction (21.72 dB m2 and 34.37 dB m2). This work provides a new avenue for developing lightweight low-/middle-frequency EMW absorbers, and will inspire the investigation of more advanced EMW absorbers with multiple magnetic components and regulated microstructures.

Soluble Gd6Cu24 clusters: effective molecular electrocatalysts for water oxidation

The water oxidation half reaction in water splitting for hydrogen production is extremely rate-limiting. This study reports the synthesis of two heterometallic clusters (Gd6Cu24-IM and Gd6Cu24-AC) for application as efficient water oxidation catalysts. Interestingly, the maximum turnover frequency of Gd6Cu24-IM in an NaAc solution of a weak acid (pH 6) was 319 s-1. The trimetallic catalytic site, H2O-GdIIICuII2-H2O, underwent two consecutive two-electron two-proton coupled transfer processes to form high-valent GdIII-O-O-CuIII2 intermediates. Furthermore, the O-O bond was formed via intramolecular interactions between the CuIII and GdIII centers. The results of this study revealed that synergistic catalytic water oxidation between polymetallic sites can be an effective strategy for regulating O-O bond formation.

Photocatalytic Generation of Divalent Lanthanide Reducing Agents

Divalent lanthanide (Ln) compounds are excellent reducing agents with unique reactivity profiles. These reagents are typically used in superstoichiometric amounts, often in combination with harmful additives. Reactions catalytic in Ln(II) reagents that retain the reactivity and selectivity of the stoichiometric transformations are currently lacking due to the absence of effective and selective methods to form reactive Ln(II) species from stable precursors. Here, active Ln(II) is generated from a Ln(III) precursor through reduction by a photoexcited coumarin or carbostyril chromophore, which, in turn, is regenerated by a sacrificial reductant. The reductant can be metallic (Zn) or organic (amines) and can be used in strictly stoichiometric amounts. A broad range of reactions, including C-halogen, C═C, C═X (X = O, N), P═O, and N═N reductions, as well as C-C, C-X (X = N, S, P), and N-N couplings were readily carried out in yields and selectivities comparable to or better than those afforded by the analogous stoichiometric transformations. The reaction outcomes could be altered by changing the ligand or the lanthanide or through the addition of environmentally benign additives (e.g., water). EPR spectroscopy supported the formation of both Ln(II) and oxidized chromophore intermediates. Taken together, these results establish photochemical Ln(II) generation as a powerful strategy for rendering Ln(II)-mediated reactions catalytic.

Chiral lanthanide-silver(I) cluster-based metal-organic frameworks exhibiting solvent stability, and tunable photoluminescence

Due to the lack of effective synthetic strategies, the preparation of chemically stable chiral Ag(I) cluster-based materials for assembly remains challenging. Here, we have developed an approach to synthesize three pairs of chiral Ln-Ag(I) cluster-based metal-organic frameworks (MOFs) named l-LnAg5-3D (Ln = Gd for 1-L, Eu for 2-L, and Tb for 3-L) and d-LnAg5-3D (Ln = Gd for 1-D, Eu for 2-D, and Tb for 3-D) by employing a chiral Ag(I) cluster ({Ag5S6}) as the node and Ln3+ ion as the inorganic linker. Structural analysis revealed that the chiral ligands induced chirality through the entire structure, resulting in a chiral helix arrangement of the C3-symmetric chiral {Ag5S6} nodes and Ln3+ ions. These compounds showed high solvent stability in various polar organic solvents. The solid-state circular dichroism (CD) spectra of compounds l-LnAg5-3D and d-LnAg5-3D exhibited obvious mirror symmetrical peaks. The emission spectra in the solid state revealed that compound 1-L only exhibited the emission peak of {Ag5S6}, while compounds 2-L and 3-L exhibited overlapping peaks of Ln3+ and {Ag5S6} at different excitation wavelengths. This demonstrates the tunable photoluminescence from {Ag5S6} to Ln3+ by introducing different Ln3+ ions and manipulating the excitation wavelengths. The study underscores the enhanced stability of Ag(I) cluster-based MOFs achieved through the incorporation of Ln3+ ions and establishes chiral Ln-Ag(I) cluster-based MOFs as promising candidates for advanced materials with tunable photoluminescence.

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.

Fabrication and application of Zn5 functionalized copolymer monolithic column for pipette tip micro-solid phase extraction of 4 polycyclic aromatic hydrocarbons in edible oil

The contamination of polycyclic aromatic hydrocarbons (PAHs) in edible oil is a health threat. Thus, trace analysis of PAHs is of high necessity. Based on the efficient adsorption of PAHs on Zn₅ metal cluster, a Zn₅ functionalized copolymer monolithic column was rationally designed for pipette tip micro-solid phase extraction (μ-SPE). The modified Zn₅ improved the adsorption selectivity and capacity of the monolith for naphthalene, phenanthrene, fluoranthene and pyrene. Chemical doping and copolymerization stabilized the monolith with a long life. Under optimal extraction conditions, a μ-SPE-high performance liquid chromatography with ultraviolet detector method was established for the detection of 4 PAHs in edible oils. The method yielded detection ranges of 0.15-250 μg L^-1 (R² > 0.997), detection limits of 0.050-1.5 μg L^-1, satisfactory recoveries (86.3-101.5 %), and high precisions (RSDs < 7.9 %). The results indicated that the Zn₅ functionalized copolymer monolithic column was an ideal separation medium for the detection of PAHs residues in edible oils.

Direct coupling of CO2 with epoxides catalyzed by lanthanum(III) supported on magnetic mesoporous organosilica nanoparticles

Lanthanum(III) supported on the magnetic mesoporous organosilica nanoparticle (La@MON) has been described as an efficient, simple, and durable heterogeneous catalyst for the synthesis of 5-membered cyclic carbonates from carbon dioxide (CO₂) and epoxides. Under optimized reaction conditions, various terminal epoxides have been converted to the corresponding carbonates in the presence of 0.3 mol% La@MON and 0.5 mol% tetrabutylammonium iodide (TBAI) as co-catalyst at relatively mild reaction conditions. It was also found that La@MON catalysts had significantly higher catalytic activity than some selected reference catalysts, which can be explained by the abundance of lanthanum(III) species acting as Lewis acidic sites for activating both carbon dioxide and epoxide molecules, along with the fact that the catalyst channels are short and provided facile mass transfer. The catalyst showed good reusability for at least five reaction cycles while the magnetic core of the catalyst helps the easy separation of the catalyst by just using an external magnet.

Heterometallic 3d-4f Alkoxide Precursors for the Synthesis of Binary Oxide Nanomaterials

In this study, a new method for the synthesis of heterometallic 3d-4f alkoxides by the direct reaction of metallic lanthanides (La, Pr, Nd, Gd) with MCl₂ (M = Mn, Ni, Co) in 2-methoxyethanol was developed. The method was applied to the synthesis of the heterometallic oxo-alkoxide clusters [Ln₄Mn₂(μ₆-O)(μ₃-OR)₈(HOR)_xCl₆] (Ln = La (1), Nd (2), Gd (3); x = 0, 2, 4); [Pr₄M₂(μ₆-O)(μ₃-OR)₈(HOR)_xCl₆] (M = Co (4), Ni (5); x = 2, 4); and [Ln₄Mn₂(μ₃-OH)₂(μ₃-OR)₄(μ-OR)₄(μ-Cl)₂(HOR)₄Cl₆] (Ln = La (11) and Pr (12)). Mechanistic investigation led to the isolation of the homo- and heterometallic intermediates [Pr(μ-OR)(μ-Cl)(HOR)Cl]_n (6), [Co₄(μ₃-OR)₄(HOR)₄Cl₄] (7), [Ni₄(μ₃-OR)₄(HOEt)₄Cl₄] (8), [Mn₄(μ₃-OR)₄(HOR)₂(HOEt)₂Cl₄] (9), and [Nd(HOR)₄Cl][CoCl₄] (10). In the presence of an external M(II) source at 1100 °C, 1-4 and 12 were selectively converted into binary metal oxide nanomaterials with trigonal or orthorhombic perovskite structures, i.e., LaMnO₃, GdMnO₃, NdMnO₃, Pr_0.9MnO₃, and PrCoO₃. Compound 5 decomposed into a mixture of homo- and heterometallic oxides. The method presented provides a valuable platform for the preparation of advanced heterometallic oxide materials with promising magnetic, luminescence, and/or catalytic applications.

Platonic and Archimedean solids in discrete metal-containing clusters

Metal-containing clusters have attracted increasing attention over the past 2-3 decades. This intense interest can be attributed to the fact that these discrete metal aggregates, whose atomically precise structures are resolved by single-crystal X-ray diffraction (SCXRD), often possess intriguing geometrical features (high symmetry, aesthetically pleasing shapes and architectures) and fascinating physical properties, providing invaluable opportunities for the intersection of different disciplines including chemistry, physics, mathematical geometry and materials science. In this review, we attempt to reinterpret and connect these fascinating clusters from the perspective of Platonic and Archimedean solid characteristics, focusing on highly symmetrical and complex metal-containing (metal = Al, Ti, V, Mo, W, U, Mn, Fe, Co, Ni, Pd, Pt, Cu, Ag, Au, lanthanoids (Ln), and actinoids) high-nuclearity clusters, including metal-oxo/hydroxide/chalcogenide clusters and metal clusters (with metal-metal binding) protected by surface organic ligands, such as thiolate, phosphine, alkynyl, carbonyl and nitrogen/oxygen donor ligands. Furthermore, we present the symmetrical beauty of metal cluster structures and the geometrical similarity of different types of clusters and provide a large number of examples to show how to accurately describe the metal clusters from the perspective of highly symmetrical polyhedra. Finally, knowledge and further insights into the design and synthesis of unknown metal clusters are put forward by summarizing these "star" molecules.

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.

Asymmetric Cyanosilylation of Aldehydes by a Lewis Acid/Base Synergistic Catalyst of Chiral Metal Clusters

Metal clusters with well-defined crystal structures are extremely useful for studying the synergistic catalytic effects and associated catalytic mechanisms. In this study, two pairs of chiral lanthanide-transition metal clusters (R)/(S)-Co₃Ln₂ (Ln = Tb or Dy) were synthesized using Schiff-base ligands [(R)- or (S)-H₃L] with multiple Lewis base sites (O sites). The as-prepared (R)/(S)-Co₃Ln₂ chiral metal clusters exhibited good catalytic functionality in the asymmetric synthesis of chiral cyanohydrins, with high conversions of up to 99% and medium-to-high enantiomeric excess values of up to 78%. The catalysis process followed a mechanism in which the bifunctional metal clusters of (R)/(S)-Co₃Ln₂, containing Lewis acid sites and Lewis base sites, simultaneously activated the aldehydes and trimethylsilyl cyanide, respectively. Consequently, synergistic catalysis was realized. The enantioselectivity of the different aldehydes and stereochemical configuration of the resulting products are attributed to the formation of a steric chiral pocket via the external chiral ligands on the clusters. In addition, heterogeneous asymmetric cyanosilylation using (R)/(S)-Co₃Ln₂ chiral metal clusters achieved high chemoselectivity and regioselectivity under mild conditions.

Organic–inorganic hybrid phosphite-participating S-shaped penta-CeIII incorporated tellurotungstate as electrochemical enzymatic hydrogen peroxide for β-D-glucose detection

Polyoxometalate chemistry has made rapid advances in innovative structural chemistry. The lower valence state and lone electron pair effect of subgroup-valence heteroatom Te(IV) can be introduced into the tungsten-oxygen system...

Assembling Lanthanide–Transition Metal Clusters on TiO2 for Photocatalytic Nitrogen Fixation

Ammonia synthesis using light with low energy consumption offers an effective solution for energy saving and environmental protection. Herein, an abundant oxygen vacancy photocatalyst was synthesized via the integration of...