Metal Exchange Method Using Au₂₅Nanoclusters as Templates for Alloy Nanoclusters with Atomic Precision

Abstract

A metal exchange method based upon atomically precise gold nanoclusters (NCs) as templates is devised to obtain alloy NCs including CuxAu25-x(SR)18, AgxAu25-x(SR)18, Cd1Au24(SR)18, and Hg1Au24(SR)18 via reaction of the template with metal thiolate complexes of Cu(II), Ag(I), Cd(II), and Hg(II) (as opposed to common salt precursors such as CuCl2, AgNO3, etc.). Experimental results imply that the exchange between gold atoms in NCs and those of the second metal in the thiolated complex does not necessarily follow the order of metal activity (i.e., galvanic sequence). In addition, the crystal structure of the exchange product (Cd1Au24(SR)18) is successfully determined, indicating that the Cd is in the center of the 13-atom icosahedral core. This metal exchange method is expected to become a versatile new approach for synthesizing alloy NCs that contain both high- and low-activity metal atoms.

Perspective: Exchange reactions in thiolate-protected metal clusters

“…In 2015, Zhu et 5(a)). 31 These results show that when [Au 25 (SR) 18 ] is used as a template, some of its metal atoms are replaced with other metals while retaining the number of metal atoms and ligands, and geometric structure. Zhu and colleagues and our studies revealed that similar reactions also occur between bimetallic/trimetallic alloy clusters and metal thiolate complexes ( Fig.…”

“…38 and 39. synthesized metal clusters as templates, it is possible to synthesize alloy clusters with a controlled number of metal atoms and ligands. Furthermore, this reaction can also be used to synthesize alloy clusters composed of elements with quite different standard redox potentials, 31,36 unlike the case of simultaneous reduction of multiple types of metal ions (simultaneous reduction method 41 ). Compared with the simultaneous reduction method, it is also possible to introduce a larger number of heteroatoms using metal exchange.…”

“…To date, the alloy clusters, such as Au 25 x Ag x (SR) 18 1, 2, 4-9), and Au 38 x Ag x (SR) 24 (x = 1-11), have been synthesized using metal exchange reactions. [31][32][33][35][36][37]39 …”

“…In metal exchange, it has been revealed that when using stable clusters as templates, metal atoms can be exchanged without affecting the number of metal atoms and ligands. Based on these findings, the formation of metal clusters with controlled isomer structure, 23 metal clusters difficult to obtain via direct synthesis, 5 and alloy clusters difficult to produce via the simultaneous reduction method 31,33 have been accessed.…”

“…Currently, the origin of the metal exchange between Au n (SR) m clusters and metal thiolate complexes or metal salts has not been clarified, although several mechanisms have been proposed. 31,36 Although Cd can be exchanged for the central atom of the Au 25 (SR) 18 cluster, 31 it is unclear why similar central exchange does not occur for Pd and Pt, which also prefer the central position. 41 In addition, in this type of Cd exchange, the exchange site (center or edge) depends on the metal source (Cd II (SC 2 H 4 Ph) 2 complex or Cd(NO 3 ) 2 ).…”