motifmediatedau25sph5pph310x2nanorodswithconjugatedelectrondelocalization

We developed a general and effective strategy to afford rod-like Au-25(SPh)(5)(PPh3)(10)X-2X-2 (X = Cl/Br) nanoclusters, capped by conjugated delocalized p electron mediated ligands. The detailed atomic structure of these materials was resolved by synchrotron radiation X-ray diffraction (SRXRD) combined with electrospray ionization mass spectrometry (ESI-MS) and UV-vis analyses. The Au-17(SR)(3)(PPh3)(6)X(2)minimum asymmetric unit, with exposed Au atoms at the center, can serve as an important model to understand the transformation of homogold nanoclusters into alloy nanoclusters. The conjugated delocalized p electrons of the thiolate ligands can effectively tune the electronic properties of the Au-25 kernel, as qualitatively evidenced by the energy gaps measured by UV-vis experiments and density functional theory (DFT) calculations. The delocalized electrons distinctly flow to the orbitals of the Au-25 kernel via the S atoms of the aromatic thiolates. The ESI-MS analysis indicates that Au-3 clusters are formed during the etching reactions, which provide an opportunity to gain insight into the intriguing conversion pathway of the Au-n(PPh3)(m)X-y precursor to the final Au-25 nanorods. Finally, the thiophenol-protected Au-25 nanorods, immobilized on activated carbon, show good catalytic activity in the aerobic oxidation of glucose to gluconic acid (74% glucose conversion and 100% selectivity for gluconic acid), much higher than that of the aliphatic Au-25 analogue. The Au-25(SPh)(5)(PPh3)(10)X-2 catalyst yields a turnover frequency (TOF) of 13.5 s(-1), higher than that of commercial catalysts such as Pd/activated carbon (AC) and Pd-Bi/AC. The insight obtained from this study will support the development and design of efficient nanogold catalysts for special oxidation reactions