The Raman spectra of a series of monolayer-protected gold clusters were investigated with special emphasis on the Au-S modes below 400 cm(-1). These clusters contain monomeric (SR-Au-SR) and dimeric (SR-Au-SR-Au-SR) gold-thiolate staples in their surface. In particular, the Raman spectra of Au-25(2-PET)(18)](0/-), Au-38(2-PET)(24), Au-40(2-PET)(24), and Au-144(2-PET)(60) (2-PET = 2-phenylethylthiol) were measured in order to study the influence of the cluster size and therefore the composition with respect to the monomeric and dimeric staples. Additionally, spectra of Au-25(2-PET)(18-2x) (S-/rac-BINAS)(x) (BINAS = 1,1'-binaphthy1-2,2'-dithiol), Au-25(CamS)(18) (CamS = 1R,4S-camphorthiol), and Au(n)BINAS(m) were measured to identify the influence of the thiolate ligand on the Au-S vibrations. The vibrational spectrum of Au-38(SCH3)(24) was calculated which allows the assignment of bands to vibrational modes of the different staple motifs. The spectra are sensitive to the size of the cluster and the nature of the ligand. Au-S-C bending around 200 cm(-1) shifts to slightly higher wavenumbers for the dimeric as compared to the monomeric staples. Radial Au-S modes (250-325 cm(-1)) seem to be sensitive toward the staple composition and the bulkiness of the ligand, having higher intensities for long staples and shifting to higher wavenumbers for sterically more demanding ligands. The introduction of only one BINAS dithiol has a dramatic influence on the Au-S vibrations because the molecule bridges two staples which changes their vibrational properties completely. Just Accepted "Just Accepted" manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides "Just Accepted" as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. "Just Accepted" manuscripts appear in full in PDF format accompanied by an HTML abstract. "Just Accepted" manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). "Just Accepted" is an optional service offered to authors. Therefore, the "Just Accepted" Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the "Just Accepted" Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these "Just Accepted" manuscripts. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 ...

The transfer of chirality from one set of molecules to another is fundamental for applications in chiral technology and has likely played a crucial role for establishing homochirality on earth. Here we show that an intrinsically chiral gold cluster can transfer its handedness to an achiral molecule adsorbed on its surface. Solutions of chiral Au38(2-PET)24 (2-PET=2-phenylethylthiolate) cluster enantiomers show strong vibrational circular dichroism (VCD) signals in vibrations of the achiral adsorbate. Density functional theory (DFT) calculations reveal that 2-PET molecules adopt a chiral conformation. Chirality transfer from the cluster to the achiral adsorbate is responsible for the preference of one of the two mirror images. Intermolecular interactions between the adsorbed molecules on the crowded cluster surface seem to play a dominant role for the phenomena. Such chirality transfer from metals to adsorbates likely plays an important role in heterogeneous enantioselective catalysis.

The far infrared spectra of a series of well-defined gold clusters covered with 2-phenylethanethiolate were studied. The spectra of the clusters are different but the differences are subtle. The Au-S stretching vibrations give rise to bands around 300 cm(-1) and below. The relative intensity of these bands changes but they shift only slightly for different clusters. A low-frequency band was identified, which is sensitive to the conformation (trans/gauche) of the 2-phenylethanethiolate ligand.

The two enantiomers of the Au40(2-PET)24 cluster were collected using HPLC and analyzed by MALDI-TOF mass spectrometry, UV-vis- and CD-spectroscopy. The flexibility of the cluster surface allows racemization of the intrinsically chiral cluster at elevated temperatures (80-130 °C) which was monitored following the optical activity. The determined activation energy (25 kcal mol(-1)) lies in the range of previously reported values for Au38 nanoclusters whereas the activation entropy deviates significantly from the one in Au38. The latter may indicate that the racemization can take place via different mechanisms.

We have studied, both experimentally and theoretically, the Raman vibrational spectra of a series of n-alkanethiolate protected Au25(SC n H2n+1)18 clusters, with n = 2, 3, 4, 5, 6, 8, 10, 12, and 14. The C–H stretching region of the infrared spectra reveals that, while shorter chains are flexible, longer chains are more ordered with a propensity toward extended all-trans conformation. The different behavior of long and short chains is also reflected in the low-frequency Raman spectra of the clusters, which are broadened for the longer chains due to interchain interactions and formation of bundles. The experimental low-frequency modes in the Raman spectra, associated with Au–S stretching vibrations, change drastically and in an apparently unsystematic way as a function of chain length. For example, a band around 320 cm–1 associated with tangential Au–S stretching character shifts up in frequency, then down and then up again as the carbon chain is increased. DFT calculations reveal that this behavior is due to a nonlinear coupling of this mode to torsional and bending modes of the alkyl chain. The frequencies of these modes strongly depend on the chain length and, as a consequence, also their coupling with the Au–S stretching modes, which explains the erratic behavior of this band in the spectra. This behavior is well described by calculations on a mimic cluster model that considers only one staple motif. For the ethanethiolate-protected cluster, the entire cluster was included in the calculation of the Raman spectrum, and this allowed for the first time to compare directly experimental and calculated Raman spectra of the same cluster. Furthermore, our study shows that the entire ligand has to be considered for the calculation of the low frequency vibrations of the Au–S interface, as this spectral region is sensitive to coupling with low-frequency ligand modes.