[Zurück]

A. Sels, G. Salassa, S. Pollitt, C. Guglieri, G. Rupprechter, N. Barrabés-Rabanal, T. Bürgi:
"Structural Investigation of the Ligand Exchange Reaction with Rigid Dithiol on Doped (Pt, Pd) Au₂₅ Clusters";
The Journal of Physical Chemistry C, 121 (2017), x; S. 10919 - 10926.

The ligand exchange reaction between heteroatom
doped (Pd, Pt) Au25(2-PET)18 (2-PET = 2-phenylethylthiolate)
clusters and enantiopure 1,1′-binaphthyl-2,2′-
dithiol (BINAS) was monitored in situ using chiral highperformance
liquid chromatography (HPLC). During the ligand
exchange reactions, replacement of two protecting thiols (2-
PET) with one new entering BINAS ligand on the cluster surface
occurs. The rigid dithiol BINAS adsorbs in a specific mode that
bridges the apex and one core site of two adjacent S(R)−Au−
S(R)−Au−S(R) units. This is the most favorable binding mode
and theoretically preserves the original structure. A kinetic
investigation on these in situ ligand exchange reactions revealed a decrease in reactivity after multiple exchange. A comparison of
relative rate constants demonstrates a similar exchange rate toward BINAS for both (Pd, Pt) systems. The possible structural
deformation after incorporation of BINAS was investigated by X-ray absorption spectroscopy (XAS) at the S K-edge and Au L3-
edge. First, a thorough assignment of all sulfur contributions to the XANES spectrum was performed, distinguishing for the first
time long and short staple motifs. Following that, a structural comparison of doped systems using XANES and EXAFS confirmed
the unaltered Au25 structure, except for some slight influence on the Au−S bonds. Additionally, an intact staple motif was
confirmed after incorporation of rigid dithiol BINAS by both XANES and EXAFS. This finding agrees with a BINAS interstaple
binding mode predicted by calculation, which does not perturb the cluster structure.

http://dx.doi.org/10.1021/acs.jpcc.6b12066

http://publik.tuwien.ac.at/files/publik_258623.pdf