Synthesis, structural characterization and transformation of an eight-electron superatomic alloy, [Au@Ag₁₉{S₂P(OPr)₂}₁₂]

Abstract

Controlling the metal nanoclusters with atomic precision is highly difficult and further studies on their transformation reactions are even more challenging. Herein we report the controlled formation of a silver alloy nanocluster [AuAg19{S2P(OnPr)2}12] (1) from an Ag20 template via a galvanic exchange route. X-ray structural analysis reveals that the alloy structure comprises of a gold-centered Ag12 icosahedron, Au@Ag12, capped by seven silver atoms. Interestingly upon reacting with one equiv. of silver(i) salt, (1) can transform into a higher nuclearity nanocluster, [Au@Ag20{S2P(OnPr)2}12]+ (2). The conversion process is studied via ESI mass spectrometry and 31P NMR spectroscopy. This kind of size-structural transformation at the single atom level is quite remarkable. Furthermore, the compositions of all the doped nanoclusters (1, 2) were fully characterized with ESI-MS and EDS. The blue shift depicted in the UV-visible and emission spectra of the doped nanoclusters (1, 2) compared with the precursor, Ag20, demonstrates that the doping atoms have significant effects on the electronic structures.

Heteroatom‐Doping Increases Cluster Nuclearity: From an [Ag20] to an [Au3Ag18] Core

“…Bakr et al synthesized [Ag 24 Au(SPhMe 2 ) 18 ] by templated galvanic reduction of Au I by [Ag 25 (SPhMe 2 ) 18 ] − . The trimetallic [AuPtAg 23 (SPhMe 2 ) 18 ] 2− cluster was synthesized using novel metal‐exchange methods by both Bakr et al and Zhu et al However we have been able to transform [Au@Ag 19 {S 2 P(O n Pr) 2 } 12 ] into a cluster of higher nuclearity with composition [Au@Ag 20 {S 2 P(O n Pr) 2 } 12 ] + after addition of an Ag + ion to the former . Due to the lack of crystal structure of the latter, which prevents detailed understanding of its surface structure, a legitimate mechanistic study in this transformation could not be achieved.…”

“…Silver and gold clusters and their alloys in subnanometer range (≤2 nm) are currently of keen scientific interests, because they exhibit molecule‐like properties such as photoluminescence, magnetism, redox behaviour, or chirality not shown by their bulk counterparts. While structurally precise thiolate‐ and selenolate‐protected gold nanoclusters with different metal nuclearities and compositions have been extensively studied, recent advances in nanoscale synthesis also led to the inventions of a few atom‐precise thiol‐ and dithiol‐capped homoleptic silver nanoclusters, for example, [Ag 44 (SR) 30 ] 4− (SR=SPhF 2 /SPhCOOH),, [Ag 25 (SPhMe 2 ) 18 ] − , [Ag 20 {S 2 P(OR) 2 } 12 ] (R=Pr, i Pr), [Ag 21 {S 2 P(O i Pr) 2 } 12 ] + , and heteroatom‐doped (Au, Pd, and Pt) Ag‐rich nanoclusters for example, [Ag 24 Au(SR) 18 ] − (R=PhMe 2 ), [MAg 24 (SR) 18 ] 2− (M=Pd/Pt; SR=2,4‐SPhCl 2 ), [Pt 1 Au 6.4 Ag 17.6 (SPhMe 2 ) 18 ] 2− , and [AuAg 19 {S 2 P(OPr) 2 } 12 ] . In addition, some mixed thiolate‐ and phosphine‐protected Ag‐rich nanoclusters, such as [Ag 29 (BDT) 12 (TPP) 4, Au 4 Ag 13 (dppm) 3 (SPhMe 2 ) 9 ], [PtAg 28 (BDT) 12 (PPh 3 ) 4 ] 4− , and [Au x Ag 50− x (dppm) 6 (SR) 30 ] , are also known (BDT=benzene‐1,3‐dithiol; TPP=Ph 3 P; dppm=bis(diphenylphosphino)methane); SR=4‐ tert ‐butylbenzyl mercaptan).…”

“…So far, all the literature reports on galvanic exchange/metal‐exchange method of heteroatom doping into homoleptic Ag thiolato nanoclusters result in product clusters with the same number of metal atoms and the shape of metal framework similar to that of the parent cluster. Two such paradigms from the literature are briefly described here.…”

Insight into the Geometric and Electronic Structures of Gold/Silver Superatomic Clusters Based on Icosahedron M13 Units and Their Alloys

“…The icosahedral M 13 unit (M=Au, Ag, Al etc. ), as a superatomic unit, has been reported for many years . As a building block, this unit can be assembled into different supramolecular structures by controlling the capping ligands .…”

Bonding of Two 8‐Electron Superatom Clusters

“…[19][20][21][22][23] Ther esearch on the superatom-superatom interactions provide nanomaterials with new structure,s uperior bonding models,a nd various properties, promote the development of chemistry and materials science. Among nanoclusters,t he icosahedral metal cores which contain 8f ree valence electrons have been widely found in many gold/silver or doped superatom clusters such as [Au 13 (PMe 2 Ph) 10 Cl 2 ] 3+ , [26] MAu 24 (SR) 18 (M = Au/Pt/ Pd), [28,29,[31][32][33][34] MAg 24 (SR) 18 (M = Au/Ag/Pt/Pd), [35][36][37] [M 1 Ag 20 {S 2 P(OiPr) 2 } 12 ] + /[M 1 Ag 20 {Se 2 P(OEt) 2 } 12 ] + (M = Ag/ Au), [38,39] [M 1 Ag 19 {S 2 P(OR) 2 } 12 ]( M = Ag/Au), [40,41] [M 1 Ag 16 -(SR) 12 ] 3À . [1] Several prototype gold superatom clusters,s uch as [Au 13 -(PMe 2 Ph) 10 Cl 2 ] 3+ (8e), [26] Au 39 (PR 3 ) 14 Cl 6 À (34e), [27] Au 25 -(SR) 18 À (8e) [28,29] and Au 102 (p-MBA) 44 (58e) [30] have been reported.…”