Zong-Jie Guan

Alkylgold complexes are of paramount significance in organometallic chemistry owing to their catalytic relevance, yet atomically precise alkylgold(0) species remain unexplored. Herein, we report the first structurally authenticated alkyl‐ligated Au(0) nanocluster, [Au ₆₄ (NHC ^{i Pr} ) ₁₄ Et ₁₀ Cl ₆ ](BF ₄ ) ₂ ( Au ₆₄ , NHC ^{i Pr} = 1,3‐diisopropylimidazolin‐2‐ylidene, Et = ethyl), synthesized via a facile base‐mediated alkylation strategy with alkylboronic acids as precursors. X‐ray crystallography reveals a box‐shaped Au ₁₆ @Au ₄₀ @Au ₈ architecture with near D _{4 h} symmetry, bearing 14 NHC ligands on the longitudinal plane and 10 alkyl ligands at both ends, all bound in a terminal coordination mode. DFT calculations demonstrate that ethyl→Au σ‐donation dominates the orbital interaction, accompanied by partial negative charge accumulation on the alkyl carbons. Although the weak nucleophilicity associated with ethyl groups, protonation of the Au–ethyl bond is thermodynamically favored, and C(sp ³ )–C(sp ³ ) cross‐coupling readily available with strong electrophiles. Notably, β‐hydride elimination of ethyl moieties is directly observed under alkaline conditions, providing the first experimental evidence for this critical transformation at Au(0) centers. This work not only establishes an efficient synthetic route to alkyl‐functionalized gold NCs but also delivers comprehensive insights into the fundamental reactivity and transformation of alkyl–gold(0) species.

Alkylgold complexes are of paramount significance in organometallic chemistry owing to their catalytic relevance, yet atomically precise alkylgold(0) species remain unexplored. Herein, we report the first structurally authenticated alkyl‐ligated Au(0) nanocluster, [Au ₆₄ (NHC ^{i Pr} ) ₁₄ Et ₁₀ Cl ₆ ](BF ₄ ) ₂ ( Au ₆₄ , NHC ^{i Pr} = 1,3‐diisopropylimidazolin‐2‐ylidene, Et = ethyl), synthesized via a facile base‐mediated alkylation strategy with alkylboronic acids as precursors. X‐ray crystallography reveals a box‐shaped Au ₁₆ @Au ₄₀ @Au ₈ architecture with near D _{4 h} symmetry, bearing 14 NHC ligands on the longitudinal plane and 10 alkyl ligands at both ends, all bound in a terminal coordination mode. DFT calculations demonstrate that ethyl→Au σ‐donation dominates the orbital interaction, accompanied by partial negative charge accumulation on the alkyl carbons. Although the weak nucleophilicity associated with ethyl groups, protonation of the Au–ethyl bond is thermodynamically favored, and C(sp ³ )–C(sp ³ ) cross‐coupling readily available with strong electrophiles. Notably, β‐hydride elimination of ethyl moieties is directly observed under alkaline conditions, providing the first experimental evidence for this critical transformation at Au(0) centers. This work not only establishes an efficient synthetic route to alkyl‐functionalized gold NCs but also delivers comprehensive insights into the fundamental reactivity and transformation of alkyl–gold(0) species.

Over the past decades, metal nanoclusters have emerged as a novel class of highly attractive materials, as they can be characterized at atomic precision, achieve complete homogeneity, and exhibit intriguing properties such as luminescence and catalytic activity. Typically, a metal nanocluster comprises a metal core and surface ligands. Despite the crucial role of the metal core, it is increasingly recognized that surface ligands are far more than mere stabilizing agents for metal nanoclusters. Compared to classical organic ligands such as thiolates and phosphines, oxygen (O) donors, including carboxylates, sulfonates, phosphinates, and phosphonates etc., have long been known but underestimated. Firstly, O donors display diverse coordination modes, making them promising candidates for generating novel architectures. Moreover, they are highly effective carriers for introducing chirality, luminescence, and other functionalities into metal nanoclusters. Additionally, most of these donors are inexpensive, readily available, stable under ambient conditions, and easy to handle. In this review, we aim to systematically summarize the development of O donor protection in atomically precise metal nanoclusters, with emphasis on the structures of surface motifs associated with O donors. The properties reported for clusters with O donor protection are also briefly surveyed. We hope this review will attract more attention to O donors as ligands for nanoclusters, which have demonstrated promising potential in generating novel structures and properties of coinage metal nanoclusters.

Great efforts have been made to establish the structure-property relationships of ligand-protected metal nanoclusters. An alkynyl-protected gold nanocluster Au₂₈(^tBuC₆H₄C≡C)₂₀ (Au₂₈-C₂) was synthesized and structurally characterized. It has an isostructural metal kernel and a quite similar ligand shell to its counterpart Au₂₈(^tBuC₆H₄S)₂₀ (Au₂₈-S), which provides a valuable platform for studying ligand effects on the luminescence of clusters. The emission intensity of Au₂₈-C₂ in solution is ∼10-fold that of Au₂₈-S. The only structural difference between these two clusters is the donor atom or group, i.e., C≡C for Au₂₈-C₂ versus S for Au₂₈-S. Temperature-dependent experiments indicate that the two Au₂₈ clusters have different thermodynamic behaviors and radiative processes. The study on the excited-state dynamics by transient absorption spectroscopy indicates that Au₂₈-C₂ has a larger triplet-state population than Au₂₈-S. This work shows important ligand effects on the emission properties of metal nanoclusters, which provide new perspectives for the designed synthesis of functional metal nanoclusters.

Tailoring the surface ligands of metal nanoclusters is important for engineering unique configurations of metal nanoclusters. Thiacalix[4]arene has found extensive applications in the construction of metal nanoclusters. In this investigation, we present the synthesis and characterization of the first all-calixarene-protected silver nanoclusters, [Ag(CH₃CN)₄]₂[Ag₄₄(BTCA)₆] (Ag₄₄, H₄BTCA = p-tert-butylthiacalix[4]arene). Single-crystal X-ray structural analysis reveals that all silver atoms are in a face-centered cubic (fcc) arrangement. The formation of such an fcc structure is attributed to the selectively passivation on {100} facets by BTCA^4-. Thiacalixarene substantially facilitates the stability of Ag₄₄ due to its multiple coordination sites and bulkiness. Mass spectrometry and theoretical calculations reveal that Ag₄₄ is a superatomic silver nanocluster with 22 free electrons in the following configuration: 1S²1P⁶1D⁶1F²2S²1D⁴. This work not only elucidates the impact of macrocyclic ligands on the stabilization of silver clusters but also furnishes an approach for assembling atomically precise fcc nanoclusters.

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 [Ag₂₁(Ph₂PO₂)₁₀(p‐CHOPhC≡C)₆]SbF₆, 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.

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 [Ag₂₁(Ph₂PO₂)₁₀(p‐CHOPhC≡C)₆]SbF₆, 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.

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 Au₂₂(C≡CR)₁₈ (R=−C₆H₄−2−F), Au₃₆(C≡CR)₂₄, Au₄₄(C≡CR)₂₈, Au₁₃₀(C≡CR)₅₀, and Au₁₄₄(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 Au₁₃₀(C≡CR)₅₀ is revealed, which presents important information for understanding the structure of the mysterious Au₁₃₀ nanoclusters. Theoretical calculations indicated Au₁₃₀(C≡CR)₅₀ has a smaller HOMO‐LUMO gap than Au₁₃₀(S−C₆H₄−4−CH₃)₅₀. This facile and reliable synthetic approach will greatly accelerate further studies on all‐alkynyl‐protected gold nanoclusters.

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 (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.

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 [μ₆‐(C₃N₆H₃)³⁻]₂−Au^I₆Ag^I₆. X‐ray single crystal structural analysis showed that a crown‐like Au^I₆Ag^I₆ macrocycle is aligned around two parallelly stacked μ₆‐(C₃N₆H₃)³⁻ moieties hold together with π–π interactions. Theoretical calculations revealed that the [μ₆‐(C₃N₆H₃)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.