UC Santa Barbara

Thiolates are a widely used ligand class for the stabilization of M(0)-containing gold and silver nanoclusters. Curiously, though, very few thiolate-stabilized Cu nanoclusters are known. Herein, we report an examination of the reactivity of RSH (R = CH₂CH₂Ph, n-Bu, n-C₁₂H₂₅) with Cu²⁺ under anhydrous conditions. These reactions result in the formation of fluorescent "Atlas-sphere"-type copper thiolate nanoclusters, including [Cu₁₂(SR')₆Cl₁₂][(Cu(R'SH))₆] (2, R' = ⁿBu) and [H(THF)₂]₂[Cu₁₇(SR'')₆Cl₁₃(THF)₂(R''SH)₃] (3, R'' = CH₂CH₂Ph), which were characterized by X-ray crystallography, electrospray ionization mass spectrometry, NMR spectroscopy, as well as X-ray absorption near-edge structure and extended X-ray absorption fine structure (EXAFS) spectroscopies. Consistent with our X-ray crystallographic results, the edge energies of 2 and 3 suggest they are constructed exclusively with Cu(I) ions. Similarly, EXAFS of 2 and 3 reveals long Cu-Cu pathlengths, which is also consistent with their X-ray crystal structures. Given these results, as well as past work on Cu²⁺/thiol reactivity, we suggest that Cu(0) is unlikely to be formed by the reaction of Cu²⁺ with a thiol and that previous reports of Cu(0)-containing nanoclusters synthesized by reaction of Cu²⁺ with thiols are likely erroneous.