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A red-near-IR dual-emissive nanocluster with the composition [Au10Ag2(2-py−C≡C)3(dppy)6](BF4)5 ( 1; 2-py−C≡C is 2-pyridylethynyl, dppy=2-pyridyldiphenylphosphine) has been synthesized. Single-crystal X-ray structural analysis reveals that 1 has a trigonal bipyramidal Au10Ag2 core that contains a planar Au4(2-py−C≡C)3 unit sandwiched by two Au3Ag(dppy)3 motifs. Cluster 1 shows intense red-NIR dual emission in solution. The visible emission originates from metal-to-ligand charge transfer (MLCT) from silver atoms to phosphine ligands in the Au3Ag(dppy)3 motifs, and the intense NIR emission is associated with the participation of 2-pyridylethynyl in the frontier orbitals of the cluster, which is confirmed by a time-dependent density functional theory (TD-DFT) calculation. [ABSTRACT FROM AUTHOR]

We report a unique intercluster compound comprising a Ag41 cage encapsulating a divacant [α-SiW10O37]10− anion and a complete [β-SiW12O40]4− anion as a counteranion. Two electro-redox centers associated with the inner and outer POM anions show interesting electrochemical behaviours, because the stable Ag41 cage acts as an electron transfer mediator. [ABSTRACT FROM AUTHOR]

The Frontispiece shows two nanoclusters are induced by the change of the surface alkynyl structures. The alkynyl −C≡C−tBu gives rise to a more spherical surface shape in 1 (red background) while −C≡CC6H4‐p‐tBu to a flat shape in 2 (green backgroud). The red and green also represent their different crystal colors and different UV/Vis properties. There are also Cl (green ball) and dppf (purple ball) surrounding these structures, suggesting co‐protection by three types of ligands. For more information, see the Full Paper Y.‐M. Lin, Q.‐M. Wang et al. on page 16029 ff. [ABSTRACT FROM AUTHOR]

The Frontispiece shows two nanoclusters are induced by the change of the surface alkynyl structures. The alkynyl −C≡C−tBu gives rise to a more spherical surface shape in 1 (red background) while −C≡CC6H4‐p‐tBu to a flat shape in 2 (green backgroud). The red and green also represent their different crystal colors and different UV/Vis properties. There are also Cl (green ball) and dppf (purple ball) surrounding these structures, suggesting co‐protection by three types of ligands. For more information, see the Full Paper Y.‐M. Lin, Q.‐M. Wang et al. on page 16029 ff. [ABSTRACT FROM AUTHOR]

By directly reducing alkynyl–silver precursors, we successfully obtained a large alkynyl‐protected silver nanocluster, (C7H17ClN)3[Ag112Cl6(C≡CAr)51], which is hitherto the largest structurally characterized silver nanocluster in the alkynyl family. The cluster exhibits four concentric core–shell structures (Ag13@Ag42@Ag48@Ag9), and four types of alkynyl–silver binding modes are observed. Chloride was found to be critical for the stabilization and formation of the silver nanocluster. The release of chloride ions in situ from CH2Cl2 solvent has been confirmed by mass spectrometry. This study suggests that the combination of alkynyl and halide ligands will pave a new way for the synthesis of large silver nanoclusters. [ABSTRACT FROM AUTHOR]

By directly reducing alkynyl–silver precursors, we successfully obtained a large alkynyl‐protected silver nanocluster, (C7H17ClN)3[Ag112Cl6(C≡CAr)51], which is hitherto the largest structurally characterized silver nanocluster in the alkynyl family. The cluster exhibits four concentric core–shell structures (Ag13@Ag42@Ag48@Ag9), and four types of alkynyl–silver binding modes are observed. Chloride was found to be critical for the stabilization and formation of the silver nanocluster. The release of chloride ions in situ from CH2Cl2 solvent has been confirmed by mass spectrometry. This study suggests that the combination of alkynyl and halide ligands will pave a new way for the synthesis of large silver nanoclusters. [ABSTRACT FROM AUTHOR]

We report a unique intercluster compound comprising a Ag41 cage encapsulating a divacant [α-SiW10O37]10− anion and a complete [β-SiW12O40]4− anion as a counteranion. Two electro-redox centers associated with the inner and outer POM anions show interesting electrochemical behaviours, because the stable Ag41 cage acts as an electron transfer mediator. [ABSTRACT FROM AUTHOR]

It is challenging to attain strong near-infrared (NIR) emissive gold nanoclusters. Here we show a rod-shaped cluster with the composition of [Au 28 (p-MBT) 14 (Hdppa) 3 ](SO 3 CF 3 ) 2 (1 for short, Hdppa is N,N-bis(diphenylphosphino)amine, p-MBT is 4-methylbenzenethiolate) has been synthesized. Single crystal X-ray structural analysis reveals that it has a rod-like face-centered cubic (fcc) Au 22 kernel built from two interpenetrating bicapped cuboctahedral Au 15 units. 1 features NIR luminescence with an emission maximum at 920 nm, and the photoluminescence quantum yield (PLQY) is 12%, which is 30-fold of [Au 21 (m-MBT) 12 (Hdppa) 2 ]SO 3 CF 3 (2, m-MBT is 3-methylbenzenethiolate) with a similar composition and 60-fold of Au 30 S(S‑t‑Bu) 18 with a similar structure. time-dependent DFT(TDDFT)calculations reveal that the luminescence of 1 is associated with the Au 22 kernel. The small Stokes shift of 1 indicates that it has a very small excited state structural distortion, leading to high radiative decay rate (k r ) probability. The emission of cluster 1 is a mixture of phosphorescence and thermally activated delayed fluorescence(TADF), and the enhancement of the NIR emission is mainly due to the promotion of k r rather than the inhibition of k nr . This work demonstrates that the metal kernel and the surface structure are both very important for cluster-based NIR luminescence materials., (© 2024. The Author(s).)

A 'passivated precursor' approach is developed for the efficient synthesis and isolation of all-alkynyl-protected gold nanoclusters. Direct reduction of dpa-passivated precursor Au-dpa (Hdpa=2,2'-dipyridylamine) in one-pot under ambient conditions gives a series of clusters including Au 22 (C≡CR) 18 (R=-C 6 H 4 -2-F), Au 36 (C≡CR) 24 , Au 44 (C≡CR) 28 , Au 130 (C≡CR) 50 , and Au 144 (C≡CR) 60 . These clusters can be well separated via column chromatography. The overall isolation yield of this series of clusters is 40 % (based on gold), which is much improved in comparison with previous approaches. It is notable that the molecular structure of the giant cluster Au 130 (C≡CR) 50 is revealed, which presents important information for understanding the structure of the mysterious Au 130 nanoclusters. Theoretical calculations indicated Au 130 (C≡CR) 50 has a smaller HOMO-LUMO gap than Au 130 (S-C 6 H 4 -4-CH 3 ) 50 . This facile and reliable synthetic approach will greatly accelerate further studies on all-alkynyl-protected gold nanoclusters., (© 2024 Wiley-VCH GmbH.)

A gold(I)-cluster-based twin-cage has been constructed by post-clustering covalent modification of a hexa-aldehyde cluster precursor with triaminotriethylamines. The cages-on-cluster structure has double cavities and four binding sites, which show site-discriminative binding for silver(I) and copper(I) guests. The guests in the tripodal hats affect the luminescence of the cluster: the tetra-silver(I) host-guest complex is weakly red-emissive, while the bis-copper(I)-bis-silver(I) one is non-emissive but is a stimuli-responsive supramolecule. The copper(I) ion inside the tri-imine cavity is oxidation sensitive, which enables the release of the bright emissive precursor cluster triggered by H 2 O 2 solution. The hybridization of a cluster with cavities to construct a cluster-based cage presents an innovative concept for functional cluster design, and the post-clustering covalent modification opens up new avenues for finely tuning the properties of clusters., (© 2024 Wiley-VCH GmbH.)

A bowl-shaped phosphangulene-protected cubic Cu 58 nanocluster has been synthesized. The structure was determined by X-ray crystallography and further analyzed by multiple techniques. The phosphangulenes not only enable ligand substitutions with triphenylphosphines in a cluster-to-cluster transformation way, but also facilitate inter-cluster interactions with fullerenes. These interactions further influence the entirety's photocurrent response and ability to liberate hydrogen when stimulated by light.

The application of supramolecular templates in aligning atomically precise heterometal arrays is important for pursuing functional materials. Herein, we report that a bilayered supramolecular tri-deprotonated melamine dimer functions as an effective template in the construction of a heterometallic gold(I)-silver(I) macrocyclic cluster [μ 6 -(C 3 N 6 H 3 ) 3- ] 2 -Au I 6 Ag I 6 . X-ray single crystal structural analysis showed that a crown-like Au I 6 Ag I 6 macrocycle is aligned around two parallelly stacked μ 6 -(C 3 N 6 H 3 ) 3- moieties hold together with π-π interactions. Theoretical calculations revealed that the [μ 6 -(C 3 N 6 H 3 ) 3- ] 2 motif dominantly contributes to the near-occupied orbitals in the electronic structure, which is closely related to its luminescence properties. This work demonstrates that the supramolecular templates containing multiple symmetric binding sites may present a facile approach in the construction of functional metal clusters., (© 2023 Wiley-VCH GmbH.)

Metal nanoclusters have emerged as promising near-infrared (NIR)-emissive materials, but their room-temperature photoluminescence quantum yield (PLQY), especially in solution, is often low (<10%). We studied the photophysics of Au 22 ( t BuPhC≡C) 18 (Au 22 ) and its alloy counterpart Au 16 Cu 6 ( t BuPhC≡C) 18 (Au 16 Cu 6 ) (where t Bu is tert -butyl and Ph is phenyl) and found that copper (Cu) doping suppressed the nonradiative decay (~60-fold less) and promoted intersystem crossing rate (~300-fold higher). The Au 16 Cu 6 nanocluster exhibited >99% PLQY in deaerated solution at room temperature with an emission maximum at 720 nanometers tailing to 950 nanometers and 61% PLQY in the oxygen-saturated solution. The approach to achieve near-unity PLQY could enable the development of highly emissive metal cluster materials.

Reported herein is the facial synthesis, molecular structure, and catalysis of a Pt/Ag nanocluster costabilized by organic ligands of phosphines and inorganic ligands of chlorides. The nanocluster with molecular formula of [PtAg 18 (dppp) 6 Cl 8 ](SbF 6 ) 2 has been obtained facilely by the one pot method. The structure of the cluster could be anatomized as the stabilizaiton of PtAg 12 -centered icosahedral core by the metalloligand of dppp-Ag-Cl, in which Cl - not only caps the surface Ag atoms but also binds the core and surface motifs. Featuring eight free electrons in its structure, the cluster exhibits high stability. More interestingly, the exposure of surface metal sites endows the cluster with counterintutively  high catalytic activity in hydrogenation reactions.

Structurally precise metal nanoclusters with a facile synthetic process and high catalytic performance have been long pursued. These atomically precise nanocatalysts are regarded as model systems to study structure-performance relationships, surface coordination chemistry, and the reaction mechanism of heterogeneous metal catalysts. Nevertheless, the research on silver-based nanoclusters for driving chemical transformations is sluggish in comparison to gold counterparts. Herein, we report the one-step synthesis of Pt/Ag alloy nanoclusters of [PtAg 9 (C 18 H 12 Br 3 P) 7 Cl 3 ](C 18 H 12 Br 3 P), which are highly active in catalysing cycloaddition reactions of CO 2 and epoxides. The cluster was obtained in a rather simple way with the reduction of silver and platinum salts in the presence of ligands in one pot. The molecular structure of the titled cluster describes the protection of the Pt-centred Ag 9 crown by the shell of phosphine ligands and halides. Its electronic structure, as revealed by density function theoretical calculations, adopts a superatomic geometry with 1S 2 1P 6 configuration. Interestingly, the cluster displays high activity in the formation of cyclic carbonates from CO 2 under mind conditions.

Photocatalytic organic conversion is considered an efficient, environmentally friendly, and energy-saving strategy for organic synthesis. In recent decades, the molecular cage has emerged as a creative functional material with broad applications in host-guest recognition, drug delivery, catalysis, intelligent materials and other fields. Based on the unique properties of porous molecular cage materials, they provide an ideal platform for leveraging pre-structuring in catalytic reactions and show great potential in various photocatalytic organic reactions. As a result, they have emerged as promising alternatives to conventional molecules or inorganic photocatalysts in redox processes. In this Review, the synthesis strategies based on coordination cages and organic cages, as well as their recent progress in photocatalytic organic conversion, are comprehensively summarized. Finally, we deliver the persistent challenges associated with porous molecular cage compounds that need to be overcome for further development in this field.

A facile strategy that directly reduces alkynyl-silver precursors and copper salts for the synthesis of bimetallic nanoclusters using the weak reducing agent Ph 2 SiH 2 is demonstrated. Two alkynyl-protected concentric-shell nanoclusters, (Ph 4 P) 2 [Ag 22 Cu 12 (C≡CR) 28 ] and (Ph 4 P) 3 [Ag 42 Cu 12 Cl(C≡CR) 36 ] (Ag 22 Cu 12 and Ag 42 Cu 12 Cl, R=bis(trifluoromethyl)phenyl), were successfully obtained and characterized by single-crystal X-ray diffraction and electro-spray ionization mass spectrometry. For the first time, a hybrid 55-atom two-shell Mackay icosahedron was found in Ag 42 Cu 12 Cl, which is icosahedral M 54 Cl instead of M 55 . The incorporation of a chloride in the metal icosahedron contributes to the stability of the cluster from both electronic and geometric aspects. Alkynyl ligands show various binding-modes including linear "RC≡C-Cu-C≡CR" staple motifs., (© 2023 Wiley-VCH GmbH.)

Functionalizing porous materials with capping agents generates hybrid materials with enhanced properties, while the challenge is how to improve the selectivity and maintain the porosity of the parent framework. Herein, we developed a "Cage-on-MOF" strategy to tune the recognition and catalytic properties of MOFs without impairing their porosity. Two types of porous coordination cages (PCCs) of opposite charges containing secondary binding groups were developed to coordinatively functionalize two distinct porous MOFs, namely MOF@PCC nanocomposites. We demonstrated that the surface-capped PCCs can act as "modulators" to effectively tune the surface charge, stability, and adsorption behavior of different host MOF particles. More importantly, the MOF@PCCs can serve as selective heterogeneous catalysts for condensation reactions to achieve reversed product selectivity and excellent recyclability. This work sets the foundation for using molecular cages as porous surface-capping agents to functionalize and manipulate another porous material, without affecting the intrinsic properties of the parent framework., (© 2023. Springer Nature Limited.)

Mimicking the active site and the substrate binding cavity of the enzyme to achieve specificity in catalytic reactions is an essential challenge. Herein, porous coordination cages (PCCs) with intrinsic cavities and tunable metal centers have proved the regulation of reactive oxygen species (ROS) generating pathways as evidenced by multiple photo-induced oxidations. Remarkably, in the presence of the Zn 4 -μ 4 -O center, PCC converted dioxygen molecules from triplet to singlet excitons, whereas the Ni 4 -μ 4 -O center promoted the efficient dissociation of electrons and holes to conduct electron transfer towards substrates. Accordingly, the distinct ROS generation behavior of PCC-6-Zn and PCC-6-Ni enables the conversion of O 2 to 1 O 2 and O 2 ⋅ - , respectively. In contrast, the Co 4 -μ 4 -O center combined the 1 O 2 and O 2 ⋅ - together to generate carbonyl radicals, which in turn reacted with the oxygen molecules. Harnessing the three oxygen activation pathways, PCC-6-M (M=Zn/Ni/Co) display specific catalytic activities in thioanisole oxidation (PCC-6-Zn), benzylamine coupling (PCC-6-Ni), and aldehyde autoxidation (PCC-6-Co). This work not only provides fundamental insights into the regulation of ROS generation by a supramolecular catalyst but also demonstrates a rare example of achieving reaction specificity through mimicking natural enzymes by PCCs., (© 2023 Wiley-VCH GmbH.)

The reduction of alkynyl-silver and phosphine-silver precursors with a weak reducing reagent Ph 2 SiH 2 led to the formation of a novel silver nanocluster [Ag 93 (PPh 3 ) 6 (C≡CR) 50 ] 3+ (R=4-CH 3 OC 6 H 4 ), which is the largest structurally characterized cluster of clusters. This disc-shaped cluster has a Ag 69 kernel consisting of a bicapped hexagonal prismatic Ag 15 unit wrapped by six Ino decahedra through edge-sharing. This is the first time that Ino decahedra are used as a building block to assemble a cluster of clusters. Moreover, the central silver atom has a coordination number of 14, which is the highest in metal nanoclusters. This work provides a diverse metal packing pattern in metal nanoclusters, which is helpful for understanding metal cluster assembling mechanisms., (© 2023 Wiley-VCH GmbH.)

Owing to the inherent instability caused by the low Cu(I)/Cu(0) half-cell reduction potential, Cu(0)-containing copper nanoclusters are quite uncommon in comparison to their Ag and Au congeners. Here, a novel eight-electron superatomic copper nanocluster [Cu 31 (4-MeO-PhC≡C) 21 (dppe) 3 ](ClO 4 ) 2 ( Cu 31 , dppe = 1,2-bis(diphenylphosphino)ethane) is presented with total structural characterization. The structural determination reveals that Cu 31 features an inherent chiral metal core arising from the helical arrangement of two sets of three Cu 2 units encircling the icosahedral Cu 13 core, which is further shielded by 4-MeO-PhC≡C - and dppe ligands. Cu 31 is the first copper nanocluster carrying eight free electrons, which is further corroborated by electrospray ionization mass spectrometry, X-ray photoelectron spectroscopy and density functional theory calculations. Interestingly, Cu 31 demonstrates the first near-infrared (750-950 nm, NIR-I) window absorption and the second near-infrared (1000-1700 nm, NIR-II) window emission, which is exceptional in the copper nanocluster family and endows it with great potential in biological applications. Of note, the 4-methoxy groups providing close contacts with neighboring clusters are crucial for the cluster formation and crystallization, while 2-methoxyphenylacetylene leads only to copper hydride clusters, Cu 6 H or Cu 32 H 14 . This research not only showcases a new member of copper superatoms but also exemplifies that copper nanoclusters, which are nonluminous in the visible range may emit luminescence in the deep NIR region.

The first mixed-valence nanocluster Cu I /Cu II with the highest percentage of Cu II ions was synthesized by using 4- tert -butylcalix[4]arene (Calix4), with the formula DMF 2 ⊂[(CO 3 ) 2- @Cu II 6 Cu I 3 (Calix4) 3 Cl 2 (DMF) 5 (H 3 O)]•DMF ( 1 ), as a photothermal nanocluster. Its structure was characterized using single-crystal X-ray diffraction, Fourier-transform infrared spectroscopy, and powder X-ray diffraction. In addition, the charge state and chemical composition of the nanocluster were determined using electrospray ionization spectrometry and X-ray photoelectron spectroscopy (XPS) spectrum. The results of the XPS and X-ray crystallography revealed that there are two independent Cu II and Cu I centers in nanocluster 1 with the relative abundances of 66.6 and 33.3% for Cu II and Cu I , respectively. The nanocluster contains three four-coordinated Cu I ions with a square-planar geometry and six five-coordinated Cu II ions with a square pyramid geometry. The nanocluster shows strong near-infrared optical absorption in the solid state and excellent photothermal conversion ability (the equilibrium temperature ∼78.2 °C) with the light absorption centers in 286-917 nm over previous reported pentanucleus Cu I 4 Cu II clusters and Cu II compounds.

Atomically precise gold nanoclusters provide great opportunities to explore the relationship between the structure and properties of nanogold catalysts. A nanocluster consists of a metal core and a surface ligand shell, and both the core and shell have significant effects on the catalytic properties. Thanks to their precise structures, the active metal site of the clusters can be readily identified and the effects of ligands on catalysis can be disclosed. In this Minireview, we summarize recent advances in catalytic research of gold nanoclusters, emphasizing four strategies for constructing open metal sites, including by post-treatment, the bulky ligands strategy, the surface geometric mismatch method, and heteroatom doping procedures. We also discuss the effects of ligands on the catalytic activity, selectivity, and stability of gold cluster catalysts. Finally, we present future challenges relating to gold cluster catalysis., (© 2022 Wiley-VCH GmbH.)

Two superatomic solids, a bi-cluster compound, [Ag 6 (3S) 4 (OTf) 4 ][Ag 6 (3S) 4 (CC t Bu) 4 ](OTf) 2 [Ag6(0)·Ag6(i)], and a homologous nanocluster, [Ag 6 (3S) 4 (tfa) 4 ] (Ag6), have been described here, which are both close-packed in the crystal lattice with the ligation of trithiane. Their aggregation-state-dependent absorption and fluorescence properties could be ascribed to the enhanced intercluster charge-transfer in the crystalline state.

Anions have been used to regulate the structures and luminescence of heterometallic clusters. Introducing ClO 4 - into orange-emissive, butterfly-like [(C)(Au-PPhpy 2 ) 6 Ag 4 ](BF 4 ) 6 (1, PPhpy 2 =bis(2-pyridyl)phenylphosphine) leads to the formation of red-emissive [(C)(Au-PPhpy 2 ) 6 Ag 5 (ClO 4 ) 3 ](ClO 4 ) 4 (2) with a novel trigonal bipyramidal structure; employing PhCO 2 - gives yellow-emissive, hexagram-like [(C)(Au-PPhpy 2 ) 6 Ag 6 (PhCO 2 ) 3 ](BF 4 ) 5 (3). Notably, 1 exhibits weak luminescence in CH 2 Cl 2 /CH 3 OH=1 : 1 (v : v) with a quantum yield (QY) of 0.05, whereas it was dramatically increased to 0.49 and 0.83 for 2 and 3, respectively. Theoretical calculation confirms that the involvement of anions in the electronic structures is responsible for the shifts of emission. The high QYs of 2 and 3 are attributed to the protection provided by ligands and anions. This work demonstrates that anions may serve as an extra designable factor beyond just counterions for functional metal clusters., (© 2022 Wiley-VCH GmbH.)

Surface organic ligands are critical in dictating the structures and properties of atomically precise metal nanoclusters. In contrast to the conventionally used thiolate, phosphine and alkynyl ligands, nitrogen donor ligands have not been used in the protection for well-defined metal nanoclusters until recently. This review focuses on recent developments in atomically precise metal nanoclusters stabilized by different types of nitrogen donor ligands, in which the synthesis, total structure determination and various properties are covered. We hope that this review will provide insights into the rational design of N donor-protected metal nanoclusters in terms of structural and functional modulation., (© 2022 Wiley-VCH GmbH.)

Copper hydrides are important hydrogenation catalysts, but their poor stability hinders the practical applications. Ligand engineering is an effective strategy to tackle this issue. An amidinate ligand, N,N'-Di(5-trifluoromethyl-2-pyridyl)formamidinate (Tf-dpf) with four N-donors has been applied as a protecting agent in the synthesis of stable copper hydride clusters: Cu 11 H 3 (Tf-dpf) 6 (OAc) 2 (Cu 11 ) with three interfacial μ 5 -H and [Cu 12 H 3 (Tf-dpf) 6 (OAc) 2 ]·OAc (Cu 12 ) with three interstitial μ 6 -H. A solvent-triggered reversible interconversion between Cu 11 and Cu 12 has been observed thanks to the flexibility of Tf-dpf. Cu 11 shows high activity in the reduction of 4-nitrophenol to 4-aminophenol, while Cu 12 displays very low activity. Deuteration experiments prove that the type of hydride is the key in dictating the catalytic activity, for the interfacial μ 5 -H species in Cu 11 are involved in the catalytic cycle whereas the interstitial μ 6 -H species in Cu 12 are not. This work highlights the role of hydrides with regard to catalytic hydrogenation activity., (© 2022. The Author(s).)

For the first time site-specific doping of silver into a spherical Au 25 nanocluster has been achieved in [Au 19 Ag 6 (MeOPhS) 17 (PPh 3 ) 6 ] (BF 4 ) 2 (Au 19 Ag 6 ) through a dual-ligand coordination strategy. Single crystal X-ray structural analysis shows that the cluster has a distorted centered icosahedral Au@Au 6 Ag 6 core of D 3 symmetry, in contrast to the I h Au@Au 12 kernel in the well-known [Au 25 (SR) 18 ] - (R = CH 2 CH 2 Ph). An interesting feature is the coexistence of [Au 2 (SPhOMe) 3 ] dimeric staples and [P-Au-SPhOMe] semi-staples in the title cluster, due to the incorporation of PPh 3 . The observation of only one double-charged peak in ESI-TOF-MS confirms the ordered doping of silver atoms. Au 19 Ag 6 is a 6e system showing a distinct absorption spectrum from [Au 25 (SR) 18 ] - , that is, the HOMO-LUMO transition of Au 19 Ag 6 is optically forbidden due to the P character of the superatomic frontier orbitals., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

An atomically resolved gold nanocluster Au 99 (C≡CC 6 H 3 -2,4-F 2 ) 40 ( Au 99 ) with an unusual 59 valence electrons has been synthesized. Single-crystal X-ray diffraction reveals that its Au 79 kernel is a Au 49 Marks decahedron capped by two Au 15 units. The surface structure of Au 99 consists of 20 linear Au(C≡CR) 2 staples. Intercluster interactions are observed between these D 5 symmetric clusters. The existence of an unpaired electron is verified by magnetic measurement. Interestingly, this open-shell gold cluster Au 99 stays intact in toluene solution at 80 °C for more than a week, and it has good charging-discharging capability under electrochemical conditions. The compact ligand shell protection around the symmetric core accounts for the high stability. This work suggests that geometric factors may play a crucial role in determining the stability of a metal nanocluster, even though the cluster has an open-shell electronic structure.

The boundary between molecular and metallic gold nanoclusters is of special interest. The difficulty in obtaining atomically precise nanoclusters larger than 2 nm limits the determination of such a boundary. The synthesis and total structural determination of the largest all-alkynyl-protected gold nanocluster (Ph 4 P) 6 [Au 156 (C≡CR) 60 ] (R = 4-CF 3 C 6 H 4 -) ( Au 156 ) are reported. It presents an ideal platform for studying the relationship between the structure and the metallic nature. Au 156 has a rod shape with the length and width of the kernel being 2.38 and 2.04 nm, respectively. The cluster contains a concentric Au 126 core structure (Au 46 @Au 50 @Au 30 ) protected by 30 linear RC≡C-Au-C≡CR staple motifs. It is interesting that Au 156 displays multiple excitonic peaks in the steady-state absorption spectrum (molecular) and pump-power-dependent excited-state dynamics as revealed in the transient absorption spectrum (metallic), which indicates that Au 156 is a critical crossover cluster for the transition from molecular to metallic state. Au 156 is the smallest-sized gold nanocluster showing metal-like electron dynamics, and it is recognized that the cluster shape is one of the important factors determining the molecular or metallic nature of a gold nanocluster.

Acetelyenediide (C 2 2- ) species have been encapsulated in bimetallic and trimetallic clusters: [(AuL) 6 Ag 7 (C≡C) 3 ](BF 4 ) 7 (2) and [(AuL) 6 AgCu 6 (C≡C) 3 ](BF 4 ) 7 (3), L=phenylbis(2-pyridyl)phosphine (PPhpy 2 ). Single-crystal X-ray diffraction analysis revealed that they are isostructural and six silver atoms in 2 are replaced with copper in 3. Both clusters have a trefoil skeleton, which can be viewed as three trigonal bipyramidal (LAu-C≡C-AuL)M 2 Ag (M=Ag/Cu) motifs sharing a common silver atom. TDDFT calculations showed Cu-doping significantly increases the energy level of (C 2 -Cu)-involved occupied orbital, thus inducing interesting transition coupling of dual-emission at low temperature. This work not only provides a strategy for constructing heterometallic clusters, but also shows the prospect for pursuing novel thermochromic luminescent materials by incorporating multi-congeneric metal components., (© 2021 Wiley-VCH GmbH.)

The first all-amidinate-protected gold nanocluster [Au 28 (Ph-form) 12 ](OTf) 2 (Ph-form=N,N'-diphenylformamidinate) (Au 28 ) has been synthesized and structurally resolved. Single crystal X-ray diffraction reveals that Au 28 has a compact Au 4 @Au 24 tetrahedral core-shell structure of T symmetry, which is fully protected by 12 bridging formamidinate ligands. This cluster is quite robust as indicated by the fact that it can stay intact in solution at 80 °C for 6 d. It exhibits excellent catalytic performance for the electroreduction of CO 2 with 96.5 % Faradaic efficiency (FE) at -0.57 V and a maximum TOF of 1731 h -1 at -0.87 V. Its superior stability is also manifested in the fact that the supported catalyst Au 28 /CNTs maintains stable potentials at ca. -0.69 V for 40 h with FE(CO)s>91 %. A superatomic electron configuration of 1S 2 1P 6 2S 2 1D 4 has been clarified by DFT computations, and the strong gold-ligand binding and geometric shell closure account for the superior stability of Au 28 ., (© 2021 Wiley-VCH GmbH.)

By directly reducing alkynyl-silver precursors, we successfully obtained a large alkynyl-protected silver nanocluster, (C 7 H 17 ClN) 3 [Ag 112 Cl 6 (C≡CAr) 51 ], which is hitherto the largest structurally characterized silver nanocluster in the alkynyl family. The cluster exhibits four concentric core-shell structures (Ag 13 @Ag 42 @Ag 48 @Ag 9 ), and four types of alkynyl-silver binding modes are observed. Chloride was found to be critical for the stabilization and formation of the silver nanocluster. The release of chloride ions in situ from CH 2 Cl 2 solvent has been confirmed by mass spectrometry. This study suggests that the combination of alkynyl and halide ligands will pave a new way for the synthesis of large silver nanoclusters., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We report the total structure determination of a covalently bonded nanocluster polymer [Au7Ag9(dppf)3(CF3CO2)7BF4]n (1). This features a one-dimensional linear chain, consisting of unique molecular building blocks, Au7Ag8(dppf)3(CF3CO2)7 clusters, which are linked together by Ag-O bonds rather than Au-Au interactions or bidentate organic bridges as previously reported.

A pair of enantiopure Au 13 nanoclusters have been enantioselectively synthesized by chiral ligands with stereogenic centers at the phosphorus atoms. Their structures are determined by X-ray crystallography, which are typical models with a high symmetric core and chiral surface ligand arrangement. Correlation between the crystallographic structure, the calculation, and the circular dichroism (CD) study indicates that helical ligand arrangement inducing the core into chiral distortion accounts for the chiroptical activities in the visible region. A rare example of cocrystallization of a mixture of diastereomers has been observed for the first time for gold nanoclusters, reflecting the lack of chiral self-sorting of the ligands.

The syntheses and properties of two bimetallic nanoclusters [Au 4 Ag 23 (C≡CtBu) 10 (dppf) 4 Cl 7 ](PF 6 ) 2 and [Au 5 Ag 24 (C≡CC 6 H 4 -p-tBu) 16 (dppf) 4 Cl 4 ](PF 6 ) 3 are reported. The Au atoms distributed in both the cores and the surface motifs are clearly determined. The two nanoclusters show distinctly different geometric structures and electronic properties, which are attributed to the subtle changes in the surface alkynyl structures., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

An alkynyl-protected gold nanocluster [Au40(PhC[triple bond, length as m-dash]C)20(dppm)4](SbF6)4 (dppm = bis(diphenylphosphino)methane) (1) has been synthesized. Single-crystal X-ray diffraction reveals that the cluster has a face-centered cubic (FCC) Au34 kernel that is made up of two Au20 units via sharing a rectangular face. Two linear PhC[triple bond, length as m-dash]C-Au-C[triple bond, length as m-dash]CPh staple motifs are located around the central part of the Au34 core, and four L-shaped PhC[triple bond, length as m-dash]C-Au-P^P staple motifs are located at the four corners of the Au34 core. Cluster 1 and [Au38(PhC[triple bond, length as m-dash]C)20(PPh3)4](CF3SO3)2 both have the FCC Au34 core, and it is found that the diphosphine ligands bringing two more Au atoms into the system have significant effects on the optical properties and stability of the clusters. The combination of a diphosphine ligand and an alkynyl ligand is helpful in generating new ligand-protected metal nanoclusters.

The controlled synthesis and structure determination of a bimetallic nanocluster Au 57 Ag 53 (C≡CPh) 40 Br 12 (Au 57 Ag 53 ) is presented. The metal core has a four-shell Au 2 M 3 @Au 34 @Ag 51 @Au 20 (M=1/3 Au+2/3 Ag) architecture. In contrast to the previously reported large nanoclusters that have highly symmetric kernel structures, the metal atoms in Au 57 Ag 53 are arranged in an irregular manner with C 1 symmetry. This cluster exhibits excellent thermal stability and is robust under oxidative or basic conditions. The silver precursors play a key role in dictating the structures of the nanoclusters, which suggests the importance of the counteranions used., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

For the first time total structure determination of homoleptic alkynyl-protected gold nanoclusters is reported. The nanoclusters are synthesized by direct reduction of PhC≡CAu, to give Au 44 (PhC≡C) 28 and Au 36 (PhC≡C) 24 . The Au 44 and Au 36 nanoclusters have fcc-type Au 36 and Au 28 kernels, respectively, as well as surrounding PhC≡C-Au-C 2 (Ph)Au-C≡CPh dimeric "staples" and simple PhC≡C bridges. The structures of Au 44 (PhC≡C) 28 and Au 36 (PhC≡C) 24 are similar to Au 44 (SR) 28 and Au 36 (SR) 24 , but the UV/Vis spectra are different. The protecting ligands influence the electronic structures of nanoclusters significantly. The synthesis of these two alkynyl-protected gold nanoclusters indicates that a series of gold nanoclusters in the general formula Au x (RC≡C) y as counterparts to Au x (SR) y can be expected., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A red-near-IR dual-emissive nanocluster with the composition [Au10 Ag2 (2-py-C≡C)3 (dppy)6 ](BF4 )5 (1; 2-py-C≡C is 2-pyridylethynyl, dppy=2-pyridyldiphenylphosphine) has been synthesized. Single-crystal X-ray structural analysis reveals that 1 has a trigonal bipyramidal Au10 Ag2 core that contains a planar Au4 (2-py-C≡C)3 unit sandwiched by two Au3 Ag(dppy)3 motifs. Cluster 1 shows intense red-NIR dual emission in solution. The visible emission originates from metal-to-ligand charge transfer (MLCT) from silver atoms to phosphine ligands in the Au3 Ag(dppy)3 motifs, and the intense NIR emission is associated with the participation of 2-pyridylethynyl in the frontier orbitals of the cluster, which is confirmed by a time-dependent density functional theory (TD-DFT) calculation., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)