Small gold clusters (approximately 1 nm) protected by molecules of a tripeptide, glutathione (GSH), were prepared by reductive decomposition of Au(I)-SG polymers at a low temperature and separated into a number of fractions by polyacrylamide gel electrophoresis (PAGE). Chemical compositions of the fractionated clusters determined previously by electrospray ionization (ESI) mass spectrometry (Negishi, Y. et al. J.Am. Chem. Soc. 2004, 126, 6518) were reassessed by taking advantage of freshly prepared samples, higher mass resolution, and more accurate mass calibration; the nine smallest components are reassigned to Au10(SG)10, Au15(SG)13, Au18(SG)14, Au22(SG)16, Au22(SG)17, Au25(SG)18, Au29(SG)20, Au33(SG)22, and Au39(SG)24. These assignments were further confirmed by measuring the mass spectra of the isolated Au:S(h-G) clusters, where h-GSH is a homoglutathione. It is proposed that a series of the isolated Au:SG clusters corresponds to kinetically trapped intermediates of the growing Au cores. The relative abundance of the isolated clusters was correlated well with the thermodynamic stabilities against unimolecular decomposition. The electronic structures of the isolated Au:SG clusters were probed by X-ray photoelectron spectroscopy (XPS) and optical spectroscopy. The Au(4f) XPS spectra illustrate substantial electron donation from the gold cores to the GS ligands in the Au:SG clusters. The optical absorption and photoluminescence spectra indicate that the electronic structures of the Au:SG clusters are well quantized; embryos of the sp band of the bulk gold evolve remarkably depending on the number of the gold atoms and GS ligands. The comparison of these spectral data with those of sodium Au(I) thiomalate and 1.8 nm Au:SG nanocrystals (NCs) reveals that the subnanometer-sized Au clusters thiolated constitute a distinct class of binary system which lies between the Au(I)-thiolate complexes and thiolate-protected Au NCs.

Solving the total structures of gold nanoclusters is of critical importance for understanding their electronic, optical and catalytic properties. Herein, we report the X-ray structure of a charge-neutral Au24(SCH2Ph-(t)Bu)20 nanocluster. This structure features a bi-tetrahedral Au8 kernel protected by four tetrameric staple-like motifs. Electronic structure analysis is further carried out and the optical absorption spectrum is interpreted. The Au24(SCH2Ph-(t)Bu)20, Au23(S-c-C6H11)16 and Au25(SCH2CH2Ph)18 nanoclusters constitute the first crystallographically characterized "trio".

A dodecanethiolate-protected Pd(1)Au(24)(SC(12)H(25))(18) cluster, which is a mono-Pd-doped cluster of the well understood magic gold cluster Au(25)(SR)(18), was isolated in high purity using solvent fractionation and high-performance liquid chromatography (HPLC) after the preparation of dodecanethiolate-protected palladium-gold bimetal clusters. The cluster thus isolated was identified as the neutral [Pd(1)Au(24)(SC(12)H(25))(18)](0) from the retention time in reverse phase columns and by elemental analyses. The LDI mass spectrum of [Pd(1)Au(24)(SC(12)H(25))(18)](0) indicates that [Pd(1)Au(24)(SC(12)H(25))(18)](0) adopts a similar framework structure to Au(25)(SR)(18), in which an icosahedral Au(13) core is protected by six [-S-Au-S-Au-S-] oligomers. The optical absorption spectrum of [Pd(1)Au(24)(SC(12)H(25))(18)](0) exhibits peaks at approximately 690 and approximately 620 nm, which is consistent with calculated results on [Pd(1)@Au(24)(SC(1)H(3))(18)](0) in which the central gold atom of Au(25)(SC(1)H(3))(18) is replaced with Pd. These results strongly indicate that the isolated [Pd(1)Au(24)(SC(12)H(25))(18)](0) has a core-shell [Pd(1)@Au(24)(SC(12)H(25))(18)](0) structure in which the central Pd atom is surrounded by a frame of Au(24)(SC(12)H(25))(18). Experiments on the stability of the cluster showed that Pd(1)@Au(24)(SC(12)H(25))(18) is more stable against degradation in solution and laser dissociation than Au(25)(SC(12)H(25))(18). These results indicate that the doping of a central atom is a powerful method to increase the stability beyond the Au(25)(SR)(18) cluster.

Several recent studies have attempted to impart [Au 25 (SR) 18 ] − with new properties by doping with foreign atoms. In this study, we studied the effect of copper doping on the electronic structure, geometric structure, and stability of [Au 25 (SR) 18 ] − with the aim of investigating the effect of foreign atom doping of [Au 25 (SR) 18 ] − . Cu n Au 25−n (SC 2 H 4 Ph) 18 was synthesized by reducing complexes formed by the reaction between metal salts (copper and gold salts) and PhC 2 H 4 SH with NaBH 4 . Mass analysis revealed that the products contained Cu n Au 25−n (SC 2 H 4 Ph) 18 (n = 1−5) in high purity. Experimental and theoretical analysis of the synthesized clusters revealed that copper doping alters the optical properties and redox potentials of the cluster, greatly distorts its geometric structure, and reduces the cluster stability in solution. These findings are expected to be useful for developing design guidelines for functionalizing [Au 25 (SR) 18 ] − through doping with foreign atoms.

Revealing the size-dependent periodicities (including formula, growth pattern, and property evolution) is an important task in metal nanocluster research. However, investigation on this major issue has been complicated, as the size change is often accompanied by a structural change. Herein, with the successful determination of the Au44(TBBT)28 structure, where TBBT = 4-tert-butylbenzenethiolate, the missing size in the family of Au28(TBBT)20, Au36(TBBT)24, and Au52(TBBT)32 nanoclusters is filled, and a neat "magic series" with a unified formula of Au8n+4(TBBT)4n+8 (n = 3-6) is identified. Such a periodicity in magic numbers is a reflection of the uniform anisotropic growth patterns in this magic series, and the n value is correlated with the number of (001) layers in the face-centered cubic lattice. The size-dependent quantum confinement nature of this magic series is further understood by empirical scaling law, classical "particle in a box" model, and the density functional theory calculations.

We report the X-ray structure of a cyclohexanethiolate-capped [Au23(SR)16](-) nanocluster (counterion: tetraoctylammonium, TOA(+)). The structure comprises a cuboctahedron-based bipyramidal Au15 kernel, which is protected by two staple-like trimeric Au3(SR)4 motifs, two monomeric Au(SR)2 and four plain bridging SR ligands. Electronic structure analysis reveals nonsuperatomic feature of [Au23(SR)16](-) and confirms the Au15 kernel and surface motifs. The Au15 kernel and trimeric staple motif are unprecedented and offer new insight in understanding the structure evolution of gold nanoclusters.

Structures of gold clusters resemble the benzene and DNA molecules and reveal a “supermolecule” origin of the magic-sized clusters.

We report the synthesis and total structure determination of a Au(24) nanocluster protected by mixed ligands of phosphine and thiolate. Single crystal X-ray crystallography and electrospray ionization mass spectrometry (ESI-MS) unequivocally determined the cluster formula to be [Au(24)(PPh(3))(10)(SC(2)H(4)Ph)(5)X(2)](+), where X = Cl and/or Br. The structure consists of two incomplete (i.e., one vertex missing) icosahedral Au(12) units joined by five thiolate linkages. This structure shows interesting differences from the previously reported vertex-sharing biicosahedral [Au(25)(PPh(3))(10)(SC(2)H(4)Ph)(5)X(2)](2+) nanocluster protected by the same type and number of phosphine and thiolate ligands. The optical absorption spectrum of Au(24) nanocluster was theoretically reproduced and interpreted.