We report the total structure of Au(38)(SC(2)H(4)Ph)(24) nanoparticles determined by single crystal X-ray crystallography. This nanoparticle is based upon a face-fused Au(23) biicosahedral core, which is further capped by three monomeric Au(SR)(2) staples at the waist of the Au(23) rod and six dimeric staples with three on the top icosahedron and other three on the bottom icosahedron. The six Au(2)(SR)(3) staples are arranged in a staggered configuration, and the Au(38)S(24) framework has a C(3) rotation axis.

We report a facile, high yielding synthetic method for preparing truly monodisperse Au(38)(SC(2)H(4)Ph)(24) nanoclusters. The synthetic approach involves two main steps: first, glutathionate (-SG) protected polydisperse Au(n) clusters (n ranging from 38 to approximately 102) are synthesized by reducing Au(I)-SG in acetone; subsequently, the size-mixed Au(n) clusters react with excess phenylethylthiol (PhC(2)H(4)SH) for approximately 40 h at 80 degrees C, which leads to Au(38)(SC(2)H(4)Ph)(24) clusters of molecular purity. Detailed studies by mass spectrometry and UV-vis spectroscopy explicitly show a gradual size-focusing process occurred in the thermal etching-induced growth process. The formula and molecular purity of Au(38)(SC(2)H(4)Ph)(24) clusters are confirmed by electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI) mass spectrometry, and size-exclusion chromatography. The optical and electrochemical properties of Au(38)(SC(2)H(4)Ph)(24) clusters show molecule-like behavior and the HOMO-LUMO gap of the cluster was determined to be approximately 0.9 eV. The size focusing growth process is particularly interesting and may be exploited to synthesize other robust gold thiolate clusters.

Since Faraday's pioneering work on gold colloids, tremendous scientific research on plasmonic gold nanoparticles has been carried out, but no atomically precise Au nanocrystals have been achieved. This work reports the first example of gold nanocrystal molecules. Mass spectrometry analysis has determined its formula to be Au 333 ðSRÞ 79 (R ¼ CH 2 CH 2 Ph). This magic sized nanocrystal molecule exhibits fcc-crystallinity and surface plasmon resonance at approximately 520 nm, hence, a metallic nanomolecule. Simulations have revealed that atomic shell closing largely contributes to the particular robustness of Au 333 ðSRÞ 79 , albeit the number of free electrons (i.e., 333 − 79 ¼ 254) is also consistent with electron shell closing based on calculations using a confined free electron model. Guided by the atomic shell closing growth mode, we have also found the next larger size of extraordinarily stability to be Au ∼530 ðSRÞ ∼100 after a size-focusing selection-which selects the robust size available in the starting polydisperse nanoparticles. This work clearly demonstrates that atomically precise nanocrystal molecules are achievable and that the factor of atomic shell closing contributes to their extraordinary stability compared to other sizes. Overall, this work opens up new opportunities for investigating many fundamental issues of nanocrystals, such as the formation of metallic state, and will have potential impact on condensed matter physics, nanochemistry, and catalysis as well.atomic precision | face-centered cubic | nanomolecule | plasmonic excitation N oble metal nanocrystals have attracted significant interest in both fundamental research and technological applications due primarily to their elegant surface plasmon resonance properties (1-6). Scientific studies on gold nanocrystals date back to Faraday's time in the nineteenth century (7). A classic procedure for the synthesis of gold nanocrystals is the citrate method, which produces quite uniform approximately 10-100 nm diameter nanocrystals with size tunable by controlling the ratio of sodium citrate to gold precursor (8, 9). Compared to the citrate-stabilized Au nanocrystals, thiolate-protected Au nanoparticles are more robust due to strong Au-SR bonds and have found important applications in biomedicine and many other fields (10-18). From the synthetic point of view, in all the previous synthetic works the obtained Au nanocrystals are more or less polydispersed, even the best quality Au nanocrystals achievable thus far-which still has a size dispersity of around 5-10%. Thus, it has long been a dream of nano-chemists to synthesize atomically precise, plasmonic nanocrystals for fundamental studies. Herein, we report the first example of atomically precise gold nanocrystals. Mass spectrometric analyses, in conjunction with other characterization, have determined its molecular formula to be Au 333 ðSRÞ 79 (where SR ¼ SCH 2 CH 2 Ph). This giant gold nanomolecule exhibits face-centered cubic (fcc) structure and surface plasmon resonance at approximately 520 ...

A golden opportunity: A mechanism has been proposed to account for the chemoselective hydrogenation of α,β‐unsaturated ketones (or aldehydes) to unsaturated alcohols catalyzed by monodisperse Au25(SR)18 particles (see picture). Now that the structure of these nanoparticles is known, structure–activity correlations can be drawn.