Unveiling the Formation Mechanism for Binary Semiconductor Nanoclusters: a Two-Step Pathway to a Double-Shell Structured Copper Sulfide Nanocluster

This work represents an important step in the quest to
unveil the
formation mechanism of atomically precise binary semiconductor nanoclusters.
In this study, we develop an acid-assisted C–S bond cleavage
approach, wherein the C–S bonds in the metal thiolate precursor
can be readily cleaved to release S2– with the assistance
of a suitable acid in the presence of Cu2O as the catalyst.
This process spontaneously fosters the formation of a [−Cu–S–Cu−]
framework and promotes the structural growth into a high nuclearity
assembly. Specifically, by employing Cu(I) tert-butyl
thiolate ([CuStBu]∞)
and carboxylate acid CH2CHCOOH as the copper/sulfur
precursor and C–S bond “scissor”, a high-nuclearity
nanocluster [S–Cu56] (Cu56S12(OOCCHCH2)12(SC(CH3)3)20) featuring a double-shell configuration has
been effectively prepared in high yield. Importantly, the [CuStBu]∞ precursor and the
intermediate [S–Cu14] (Cu14(StBu)8(OOCCHCH2)6) cluster have also been successfully isolated and structurally
characterized, which ultimately enables the establishment of a two-step
formation pathway for the [S–Cu56] nanocluster.
Furthermore, in contrast to conventional reduction synthetic routes
for metal nanoclusters containing Cu(0) or Cu(I), the acid-assisted
C–S bond cleavage approach represents an oxidation process
with respect to the constituent metals, yielding highly charged Cu(II)
cations in the copper sulfide nanocluster.