Search

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.)

Due to the stability issue, It is difficult to prepare a silver nanocluster bearing functional sites, especially at a large scale. We report the synthesis and structure of a stable silver nanocluster bearing multiple surface aldehyde groups [Ag 21 (Ph 2 PO 2 ) 10 (p-CHOPhC≡C) 6 ]SbF 6 , which allows for postsynthesis modification such as surface functionalization through aldimine condensation to give homochiral clusters. Remarkably, the preparation of this cluster can be done in ~90 % high yield at gram scale, which facilitates further studies and potential applications. Through DFT calculations and geometric structure analysis, the high stability of this cluster is attributed to the geometric closure and electronic structure. This is the first time that an effective one-pot method has been developed to synthesize functional silver nanoclusters in high yield. The title cluster will be useful in the development of a variety of cluster-based materials., (© 2024 Wiley-VCH GmbH.)

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.)

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.)

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.)

We report the structures, stability and catalysis properties of two Ag 21 nanoclusters, namely [Ag 21 (H 2 BTCA) 3 (O 2 PPh 2 ) 6 ]SbF 6 (1) and [Ag 21 (C≡CC 6 H 3 -3,5-R 2 ) 6 (O 2 PPh 2 ) 10 ]SbF 6 (2) (H 4 BTCA=p-tert-butylthiacalix[4]arene, R=OMe). Both Ag 21 structures possess an identical icosahedral kernel that is surrounded by eight peripheral Ag atoms. Single-crystal structural analysis and ESI-MS revealed that 1 is an 8-electron cluster and 2 has four free electrons. Theoretical results show that the P-symmetry orbitals are found as HOMO-1 and HOMO states in 1, and the frontier unoccupied molecular orbitals (LUMO, LUMO+1 and LUMO+2) show D-character, indicating 1 is a superatomic cluster with an electronically closed shell 1S 2 1P 6 , while 2 has an incomplete shell configuration 1S 2 1P 2 . These two Ag 21 clusters show superior stability under ambient conditions, and 1 is robust even at 90 °C in toluene and under oxidative conditions (30 % H 2 O 2 ). Significantly, 2 exhibits much higher activity than 1 as catalyst in the reduction of 4-nitrophenol. This work demonstrates that ligands can influence the electronic structures of silver clusters, and further affect their stability and catalytic performance., (© 2022 Wiley-VCH GmbH.)

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.)

The synthesis and isolation of alkynyl/chloride-protected gold nanoclusters is described. Silica gel column chromatography is effective in isolating gold nanoclusters from the as-synthesized cluster mixture to give the clusters Na[Au 25 L 18 ] (Au 25 ), [HNEt 3 ] 3 [Au 67 L 32 Cl 4 ] (Au 67 ), [HNEt 3 ] 4 [Au 106 L 40 Cl 12 ] (Au 106 ), L=3,5-bis(trifluoromethyl)-phenylacetylide. Au 67 and Au 106 are new clusters; the structures were determined by X-ray single-crystal diffraction. Au 67 contains a distorted Au 18 Marks decahedron shelled by an irregular Au 32 and further protected with two V-shaped Au 2 L 3 , 13 linear AuL 2 staples and 4 chlorides. Au 67 is the first structurally determined 34e superatomic gold nanocluster. Au 106 is composed of 106 Au atoms co-protected by alkynyls and chlorides. It has a Au 79 kernel, like in Au 102 (p-MBA) 44 . The surface structure of Au 106 includes 20 linear Au-alkynyl staples, 5 Cl-Au-Cl and 2 Cl-Au motifs. These three gold nanoclusters show size-dependent electrochemical properties., (© 2020 Wiley-VCH GmbH.)

Gold nanoclusters with surface open sites are crucial for practical applications in catalysis. We have developed a surface geometric mismatch strategy by using mixed ligands of different type of hindrance. When bulky phosphine Ph 3 P and planar dipyridyl amine (Hdpa) are simultaneously used, steric repulsion between the ligands will reduce the ligand coverage of gold clusters. A well-defined access granted gold nanocluster [Au 23 (Ph 3 P) 10 (dpa) 2 Cl](SO 3 CF 3 ) 2 (Au 23 , dpa=dipyridylamido) has been successfully synthesized. Single crystal structural determination reveals that Au 23 has eight uncoordinated gold atoms in the shape of a distorted bicapped triangular prism. The accessibility of the exposed Au atoms has been confirmed quantitatively by luminescent titration with 2-naphthalenethiol. This cluster has excellent performance toward selective oxidation of benzyl alcohol to benzaldehyde and demonstrates excellent stability due to the protection of negatively charged multidentate ligand dpa., (© 2020 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.)

Two homoleptic alkynyl-protected gold clusters with compositions of Na[Au 25 (C≡CAr) 18 ] and (Ph 4 P)[Au 25 (C≡CAr) 18 ] (Na⋅1 and Ph 4 P⋅1, Ar=3,5-bis(trifluoromethyl)phenyl) were synthesized via a direct reduction method. 1 is a magic cluster analogous to [Au 25 (SR) 18 ] - in terms of electron counts and metal-to-ligand ratio. Single-crystal structure analysis reveals that 1 has an identical Au 13 kernel to [Au 25 (SR) 18 ] - , but adopts a distinctly different arrangement of the six peripheral dimer staple motifs. The steric hindrance of alkynyl ligands is responsible for the D 3 arrangement of Au 25 . The introduction of alkynyl also significantly changes the optical absorption features of the nanocluster as supported by DFT calculations. This magic cluster confirms that there is a similar but quite different parallel alkynyl-protected metal cluster universe in comparison to the thiolated one., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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.)

An intensely luminescent gold(I)-silver(I) cluster [(C)(AuPPhpy 2 ) 6 Ag 6 (CF 3 CO 2 ) 3 ](BF 4 ) 5 (PPhpy 2 =bis(2-pyridyl)phenylphosphine) (3) is synthesized by the reaction of [(C)(AuPPhpy 2 ) 6 Ag 4 ](BF 4 ) 6 with AgCF 3 CO 2 . All eight faces of the octahedral C@Au 6 core in 3 are capped, that is, six faces are capped by silver ions and two by tetrafluoroborates. Cluster 3 is intensely luminescent in solution with a quantum yield of 92 %. Ligation of CF 3 CO 2 - ions is vital for the construction and emission properties of 3, as confirmed by DFT calculations. BF 4 - ions are involved in the protecting sphere of the metal core, as evidenced by 19 F NMR data. The participation of phosphines, CF 3 CO 2 - , and BF 4 - ions in the protection of the emissive core and the enhancement of the rigidity of the cluster result in the high emission efficiency. This is the first example of organic ligands and inorganic anions forming a rigid protecting sphere for luminescent coinage-metal clusters., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)