Ag-S Type Quantum Dots versus Superatom Nanocatalyst: A Single Sulfur Atom Modulated Decarboxylative Radical Cascade Reaction

The preparation of high-nuclearity silver nanoclusters in quantitative yield remains exclusive and their potential applications in the catalysis of organic reactions are still undeveloped. Here, we have synthesized a quantum dot (QD)-based catalyst, [Ag62S13(SBut)32](PF6)4 (denoted as Ag62S12-S) in excellent yield that enables the direct synthesis of pharmaceutically precious 3,4dihydroquinolinone in 92% via a decarboxylative radical cascade reaction of cinnamamide with alpha-oxocarboxylic acid under mild reaction conditions. In comparison, a superatom [Ag62S12(SBut)32]- (PF6)2 (denoted as Ag62S12) with identical surface anatomy and size, but without a central S2- atom in the core, gives an improved yield (95%) in a short time and exhibits higher reactivity. Multiple characterization techniques (single-crystal X-ray diffraction, nuclear magnetic resonance (1H and 31P), electrospray ionization mass spectrometry, energy dispersive X-ray spectroscopy, Brunauer-Emmett-Teller (BET), Fourier-transform infrared spectroscopy, Xray photoelectron spectroscopy, and thermogravimetric analysis) confirm the formation of Ag62S12-S. The BET results expose the total active surface area in supporting a single e- transfer reaction mechanism. Density functional theory reveals that leaving the central S atom of Ag62S12-S leads to higher charge transfer from Ag62S12 to the reactant, accelerates the decarboxylation process, and correlates the catalytic properties with the structure of the nanocatalyst.

Automated summary

In this study, a quantum dot-based catalyst with high quantum yield was successfully synthesized for the catalysis of organic reactions in the synthesis of pharmaceutically precious compounds. Compared to a superatom without a central S2- atom, the catalyst showed higher catalytic activity in terms of yield and reaction time.