School Of Basic And Applied Sciences

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    Ag-S Type Quantum Dots versus Superatom Nanocatalyst: A Single Sulfur Atom Modulated Decarboxylative Radical Cascade Reaction
    (American Chemical Society, 2023-04-06T00:00:00) Meena, Sangeeta; Dastider, Saptarshi G.; Nishad, Chandra Shekhar; Jangid, Dilip Kumar; Kumar, Pankaj; Khirid, Samreet; Bose, Shubhankar Kumar; Mondal, Krishnakanta; Banerjee, Biplab; Dhayal, Rajendra S.
    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 3,4-dihydroquinolinone in 92% via a decarboxylative radical cascade reaction of cinnamamide with ?-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, X-ray 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. � 2023 American Chemical Society.
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    [Ag20{S2P(OR)2}12]: A Superatom Complex with a Chiral Metallic Core and High Potential for Isomerism
    (Wiley-VCH Verlag, 2016) Dhayal, R.S.; Lin, Y.-R.; Liao, J.-H.; Chen, Y.-J.; Liu, Y.-C.; Chiang, M.-H.; Kahlal, S.; Saillard, J.-Y.; Liu, C.W.
    The synthesis and structural determination of a silver nanocluster [Ag20{S2P(OiPr)2}12] (2), which contains an intrinsic chiral metallic core, is produced by reduction of one silver ion from the eight-electron superatom complex [Ag21{S2P(OiPr)2}12](PF6) (1) by borohydrides. Single-crystal X-ray analysis displays an Ag20core of pseudo C3symmetry comprising a silver-centered Ag13icosahedron capped by seven silver atoms. Its n-propyl derivative, [Ag20{S2P(OnPr)2}12] (3), can also be prepared by the treatment of silver(I) salts and dithiophosphates in a stoichiometric ratio in the presence of excess amount of [BH4]?. Crystal structure analyses reveal that the capping silver-atom positions relative to their icosahedral core are distinctly different in 2 and 3 and generate isomeric, chiral Ag20cores. Both Ag20clusters display an emission maximum in the near IR region. DFT calculations are consistent with a description within the superatom model of an 8-electron [Ag13]5+core protected by a [Ag7{S2P(OR)2}12]5?external shell. Two additional structural variations are predicted by DFT, showing the potential for isomerism in such [Ag20{S2P(OR)2}12] species. ? 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim