Structural Information on the Au–S Interface of Thiolate-Protected Gold Clusters: A Raman Spectroscopy Study

Abstract

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 ...

Fine structure of gold nanoparticles stabilized by buthyldithiol: Species identified by Mössbauer spectroscopy

“…The third component can be assigned to surface gold [29] in good correspondence with the quadrupole splitting values shown in Table 1. The fourth component can probably be originated from the middle of the mentioned bridging "staples", namely from gold atoms removed from the metallic surface and located in between two sulphurs, in good correspondence with data reported earlier for this S Au(I) S component [3,4,21,23,29]. It is worth noticing that the fraction of the surface components extracted from the relative intensity values shown in Table 1 is 53%.…”

“…5B). Appearance of an intense band at 285 cm −1 clearly attests for the presence of Au S bonds in good correspondence with [4]. Other characteristic bands also appear, namely symmetrical skeleton vibration at 1035 cm −1 , bending and valence vibrations for CH 2 at 1452 and 2926-2853 cm −1 , respectively.…”

“…Beside the Au S linear bonds additional monomeric (Au metal -SRAu(I)-SR-Au metal ) and dimeric (Au metal -SR-Au(I)-SR-Au(I)-SRAu metal ) "staples" can be formed in large molecular complexes, containing only a few dozens of core gold atoms. These structures are dominant at small thiolate encapped Au m (10 < m < 45) molecular clusters [2,4,21,22] and they can be observed on the sur face of larger particles as well [3,23]. On well-developed crystal faces of larger particles thiol molecules may form self-assembled monolayers [24].…”

“…In the low size range there are certain x values for Au x clusters at which their stabilization is preferred (25, 38, 55, 144, etc. ) [2][3][4][5]. Transition from these large molecular complexes (exhibiting separate valence bands) to metallic particles is around at Au 55 , i.e.…”

Raman spectra from ab initio molecular dynamics and its application to liquid S-methyloxirane

“…KS-DFT was used as the electronic structure method in the framework of the Gaussian and plane waves formalism. We tested three different density functionals: BP86, 48,49 that has been found to perform well in static frequency calculations within the doubleharmonic approximation, [50][51][52][53][54][55][56][57][58][59][60][61][62][63] 73,74 for comparing purposes. BLYP-Goedecker-Teter-Hutter (GTH) (in case of PBE the PBE-GTH) pseudopotentials [75][76][77] and the TZVP-GTH and DZVP-GTH basis sets were applied.…”