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Understanding the critical roles of ligands ( e.g. thiolates, SR) in the formation of metal nanoclusters of specific sizes has long been an intriguing task since the report of ligand exchange-induced transformation of Au 38 (SR) 24 into Au 36 (SR′) 24 . Herein, we conduct a systematic study of ligand exchange on Au 38 (SC 2 H 4 Ph) 24 with 21 incoming thiols and reveal that the size/structure preference is dependent on the substituent site. Specifically, ortho -substituted benzenethiols preserve the structure of Au 38 (SR) 24 , while para - or non-substituted benzenethiols cause its transformation into Au 36 (SR) 24 . Strong electron-donating or -withdrawing groups do not make a difference, but they will inhibit full ligand exchange. Moreover, the crystal structure of Au 38 (SR) 24 (SR = 2,4-dimethylbenzenethiolate) exhibits distinctive π⋯π stacking and “anagostic” interactions (indicated by substantially short Au⋯H distances). Theoretical calculations reveal the increased energies of frontier orbitals for aromatic ligand-protected Au 38 , indicating decreased electronic stability. However, this adverse effect could be compensated for by the Au⋯H–C interactions, which improve the geometric stability when ortho -substituted benzenethiols are used. Overall, this work reveals the substituent site effects based on the Au 38 model, and highlights the long-neglected “anagostic” interactions on the surface of Au-SR NCs which improve the structural stability. 

Atomically precise nanoclusters of coinage metals in the 1–3 nm size regime have been intensively pursued in recent years. Such nanoclusters are attractive as they fill the gap between small molecules (<1 nm) and regular nanoparticles (>3 nm). This intermediate identity endows nanoclusters with unique physicochemical properties and provides nanochemists opportunities to understand the fundamental science of nanomaterials. Metal nanoparticles are well known to exhibit plasmon resonances upon interaction with light; however, when the particle size is downscaled to the nanocluster regime, the plasmons fade out and step-like absorption spectra characteristic of cluster sizes are manifested due to strong quantum confinement effects. Recent research has revealed that nanoclusters are commonly composed of a distinctive kernel and a surface-protecting shell (or staple-like metal–ligand motifs). Understanding the kernel configuration and evolution is one of the central topics in nanoscience research. This Review summarizes the recent progress in identifying the growth patterns of atomically precise coinage nanoclusters. Several basic kernel units have been observed, such as the M 4 , M 13 and M 14 polyhedrons (where, M = metal atom). Among them, the tetrahedral M 4 and icosahedral M 13 units are the most common ones, which are adopted as building blocks to construct larger kernel structures via various fusion or aggregation modes, including the vertex- and face-sharing mode, the double-strand and alternate single-strand growth, and cyclic fusion of units, as well as the fcc-based cubic growth pattern. The identification of the kernel growth pathways has led to deeper understanding of the evolution of electronic structure and optic properties. 

Deciphering the complicated excited-state process is critical for the development of luminescent materials with controllable emissions in different applications. Here we report the emergence of a photo-induced structural distortion accompanied by an electron redistribution in a series of gold nanoclusters. Such unexpected slow process of excited-state transformation results in near-infrared dual emission with extended photoluminescent lifetime. We demonstrate that this dual emission exhibits highly sensitive and ratiometric response to solvent polarity, viscosity, temperature and pressure. Thus, a versatile luminescent nano-sensor for multiple environmental parameters is developed based on this strategy. Furthermore, we fully unravel the atomic-scale structural origin of this unexpected excited-state transformation, and demonstrate control over the transition dynamics by tailoring the bi-tetrahedral core structures of gold nanoclusters. Overall, this work provides a substantial advance in the excited-state physical chemistry of luminescent nanoclusters and a general strategy for the rational design of next-generation nano-probes, sensors and switches.

 

Recent advances in the synthetic chemistry of atomically precise metal nanoclusters (NCs) have significantly broadened the accessible sizes and structures. Such particles are well defined and have intriguing properties, thus, they are attractive for catalysis. Especially, those NCs with identical size but different core (or surface) structure provide unique opportunities that allow the specific role of the core and the surface to be mapped out without complication by the size effect. Herein, we summarize recent work with isomeric Au_nNCs protected by ligands and isostructural NCs but with different surface ligands. The highlighted work includes catalysis by spherical and rod‐shaped Au₂₅(with different ligands), quasi‐isomeric Au₂₈(SR)₂₀with different R groups, structural isomers of Au₃₈(SR)₂₄(with identical R) and Au₃₈S₂(SR)₂₀with body‐centred cubic (bcc) structure, and isostructural [Au₃₈L₂₀(PPh₃)₄]²⁺(different L). These isomeric and/or isostructural NCs have provided valuable insights into the respective roles of the kernel, surface staples, and the type of ligands on catalysis. Future studies will lead to fundamental advances and development of tailor‐made catalysts.

 

Recent advances in the synthetic chemistry of atomically precise metal nanoclusters (NCs) have significantly broadened the accessible sizes and structures. Such particles are well defined and have intriguing properties, thus, they are attractive for catalysis. Especially, those NCs with identical size but different core (or surface) structure provide unique opportunities that allow the specific role of the core and the surface to be mapped out without complication by the size effect. Herein, we summarize recent work with isomeric Au_nNCs protected by ligands and isostructural NCs but with different surface ligands. The highlighted work includes catalysis by spherical and rod‐shaped Au₂₅(with different ligands), quasi‐isomeric Au₂₈(SR)₂₀with different R groups, structural isomers of Au₃₈(SR)₂₄(with identical R) and Au₃₈S₂(SR)₂₀with body‐centred cubic (bcc) structure, and isostructural [Au₃₈L₂₀(PPh₃)₄]²⁺(different L). These isomeric and/or isostructural NCs have provided valuable insights into the respective roles of the kernel, surface staples, and the type of ligands on catalysis. Future studies will lead to fundamental advances and development of tailor‐made catalysts.