Homoleptic Silver-Rich Trimetallic M20 Nanocluster

Doping effect on a two-electron silver nanocluster

This study investigates the effects of metal addition and doping of a 2-electron silver superatom, [Ag10{S2P(OiPr)2}8] (Ag10). When Ag+ is added to Ag10 in THF solution, [Ag11{S2P(OiPr)2}8(OTf)] (Ag11) is rapidly formed almost quantitatively. When the same method is used with Cu+, a mixture of alloys, [CuxAg11-x{S2P(OiPr)2}8]+ (x = 1-3, CuxAg11-x), is obtained. In contrast, introducing Au+ to Ag10 leads to decomposition. The structural and compositional analysis of Ag11 was characterized by single-crystal X-ray diffraction (SCXRD), ESI-MS, NMR spectroscopy, and DFT calculations. While no crystal structure was obtained for CuxAg11-x, DFT calculations provide insights into potential sites for copper location. The absorption spectrum exhibits a notable blue shift in the low-energy band after copper doping, contrasting with that of the slight shift observed in 8-electron Cu-doped Ag nanoclusters. Ag11 and CuxAg11-x are strongly emissive at room temperature, and solvatochromism across different organic solvents is highlighted. This study underscores the profound influence of metal addition and doping on the structural and optical properties of silver nanoclusters, providing important contributions to understanding the nanoclusters and their photophysical behaviors.

Recent progress in dichalcophosphate coinage metal clusters and superatoms

Atomically precise clusters of group 11 metals (Cu, Ag, and Au) attract considerable attention owing to their remarkable structure and fascinating properties. One of the unique subclasses of these clusters is based on dichalcophosphate ligands of [(RO)₂PE₂]^- type (E = S or Se, and R = alkyl). These ligands successfully stabilise the most diverse Cu, Ag, and Au clusters and superatoms, spanning from simple ones to amazing assemblies featuring unusual structural and bonding patterns. It is noteworthy that such complicated clusters are assembled directly from cheap and simple reagents, metal(I) salts and dichalcophosphate anions. This reaction, when performed in the presence of a hydride or other anion sources, or foreign metal ions, results in hydrido- or anion-templated homo- or heteronuclear structures. In this feature article, we survey the recent advances in this exciting field, highlighting the powerful synthetic capabilities of the system "a metal(I) salt - [(RO)₂PX₂]^- ligands - a templating anion or borohydride" as an inexhaustible platform for the creation of new atomically precise clusters, superatoms, and nanoalloys.

Galvanic replacement-induced introduction of a heteroligand into bimetallic and trimetallic nanoclusters

Heteroleptic 8-electron silver-rich alloy nanoclusters, [Au@Au₄Ag₁₂(dtp)₇(PPh₃)₄]²⁺ (1) and [Pt@Au₄Ag₁₁(dtp)₇(PPh₃)₄] (2), were successfully synthesized via a galvanic replacement reaction of 1,1-dithiolate-protected M@Ag₂₀ (M = Au and Pt) nanoclusters with Au(I)-phosphine salts, leading to the alteration of the cluster nuclearity and geometry of shell skeletons but retaining the same 8-electron count.

Superatom Pruning by Diphosphine Ligands as a Chemical Scissor

A two-electron silver superatom, [Ag₆{S₂P(OⁱPr)₂}₄(dppm)₂] (1), was synthesized by adding dppm (bis(diphenylphosphino)methane) into [Ag₂₀{S₂P(OⁱPr)₂}₁₂] (8e). It was characterized by single-crystal crystallography, multinuclear NMR spectroscopy, electrospray ionization-mass spectrometry, density functional theory (DFT), and time-dependent DFT calculations. The added dppm ligands, which carry out the nanocluster-to-nanocluster transformation, act as a chemical scissor to prune the nanocluster geometrically from an icosahedron-based Ag₂₀ nanocluster (NC) to an octahedral Ag₆ NC and electronically from eight-electron to two-electron. Eventually, dppm was involved in the protective shell to form a new heteroleptic NC. The temperature-dependent NMR spectroscopy confirms its fluxional behavior, showing the fast atomic movement at ambient temperature. Compound 1 exhibits a bright yellow emission under UV irradiation at ambient temperature with a quantum yield of 16.3%. This work demonstrates a new methodology to achieve nanocluster-to-nanocluster transformation via stepwise synthesis.

Hydride-Containing Eight-Electron Pt/Ag Superatoms: Structure, Bonding, and Multi-NMR Studies

Recent reports on hydride-doped noble metal nanoclusters strongly suggest that the encapsulated hydride is a part of the superatom core, but no accurate location of the hydride could be experimentally proved, so far. We report herein a hydride-doped eight-electron platinum/silver alloy nanocluster in which the position of four-coordinated hydride was determined by neutron diffraction for the first time. X-ray structures of [PtHAg₁₉(dtp/desp)₁₂] (dtp = S₂P(OⁿPr)₂, 1; dsep = Se₂P(OⁱPr)₂, 2) describe a central platinum hydride (PtH) unit encapsulated within a distorted Ag₁₂ icosahedron, the resulting (PtH)@Ag₁₂ core being stabilized by an outer sphere made up of 7 capping silver atoms and 12 dichalcogenolates. Solid-state structures of 1 and 2 differ somewhat in the spatial configuration of their outer spheres, resulting in overall different symmetries, C₁ and C₃, respectively. Whereas the multi-NMR spectra of 2 in solution at 173 K reveal that the structure of C₃ symmetry is the predominant one, ¹H and ¹⁹⁵Pt NMR spectra of 1 at the same temperature disclose the presence of isomers of both C₁ and C₃ symmetry. DFT calculations found both isomers to be very close in energy, supporting the fact that they co-exist in solution. They also show that the [PtH@Ag₁₂]⁵⁺ kernel can be viewed as a closed-shell superatomic core, the μ₄-hydride electron contributing to its eight-electron count. On the other hand, the 1s(H) orbital contributes only moderately to the superatomic orbitals, being mainly involved in the building of a Pt-H bonding electron pair with the 5d_z²(Pt) orbital.