Racemization of a chiral nanoparticle evidences the flexibility of the gold-thiolate interface.
Thiolate-protected gold nanoparticles and clusters combine size-dependent physical properties with the ability to introduce (bio)chemical functionality within their ligand shell. The engineering of the latter with molecular precision is an important prerequisite for future applications. A key question in this respect concerns the flexibility of the gold-sulfur interface. Here we report the first study on racemization of an intrinsically chiral gold nanocluster, Au38(SCH2CH2Ph)24, which goes along with a drastic rearrangement of its surface involving place exchange of several thiolates. This racemization takes place at modest temperatures (40-80 °C) without significant decomposition. The experimentally determined activation energy for the inversion reaction is ca. 28 kcal/mol, which is surprisingly low considering the large rearrangement. The activation parameters furthermore indicate that the process occurs without complete Au-S bond breaking.
Department of Physical Chemistry, University of Geneva , 30 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland.
Stefan
S
Knoppe
Igor
I
Dolamic
Thomas
T
Bürgi
D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D006046:Gold / Q000737:chemistry*; D007536:Isomerism; D053768:Metal Nanoparticles / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013438:Sulfhydryl Compounds / Q000138:chemical synthesis / Q000737:chemistry*
D013438:Sulfhydryl Compounds; D006046:Gold