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New Magic Au₂₄ Cluster Stabilized by PVP: Selective Formation, Atomic Structure, and Oxidation Catalysis.

ABSTRACT: An unprecedented magic number cluster, Au₂₄Cl _x (x = 0-3), was selectively synthesized by the kinetically controlled reduction of the Au precursor ions in a microfluidic mixer in the presence of a large excess of poly(N-vinyl-2-pyrrolidone) (PVP). The atomic structure of the PVP-stabilized Au₂₄Cl _x was investigated by means of aberration-corrected transmission electron microscopy (ACTEM) and density functional theory (DFT) calculations. ACTEM video imaging revealed that the Au₂₄Cl _x clusters were stable against dissociation but fluctuated during the observation period. Some of the high-resolution ACTEM snapshots were explained by DFT-optimized isomeric structures in which all the constituent atoms were located on the surface. This observation suggests that the featureless optical spectrum of Au₂₄Cl _x is associated with the coexistence of distinctive isomers. X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy of CO adsorbates revealed the electron-rich nature of Au₂₄Cl _x clusters due to the interaction with PVP. The Au₂₄Cl _x :PVP clusters catalyzed the aerobic oxidation of benzyl alcohol derivatives without degradation. Hammett analysis and the kinetic isotope effect indicated that the hydride elimination by Au₂₄Cl _x was the rate-limiting step with an apparent activation energy of 56 ± 3 kJ/mol, whereas the oxygen pressure dependence of the reaction kinetics suggested the involvement of hydrogen abstraction by coadsorbed O₂ as a faster process.

SUBMITTER: Hasegawa S

PROVIDER: S-EPMC8395683 | biostudies-literature |

REPOSITORIES: biostudies-literature

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