Von Gold‐Clustern zu Gold‐Kolloiden

Abstract

Aurophilic interactions, attractive interactions between the gold atoms, play an important role in the structural chemistry of Au(I) complexes. This is also true for gold(I) clusters, where therefore bridging groups are often unnecessary to build up the cluster core. In „metalloid“ clusters, which may contain several hundreds of gold atoms, gold has an average oxidation number between zero and one. Such clusters consist of a ligand-free core and a ligand-containing shell of metal atoms. Having defined structures, they are model systems for gold colloids, where the size distribution of the metal particles is more or less broad. Gold colloids are colored, the colors depending on the particle size. Structurally defined clusters allow investigating at which size the nonmetallic-metallic transition occurs. It starts at about 150 gold atoms; at about 250 atoms the particles are metallic. The transitions from molecular coordination compounds via clusters and particles to metallic gold are smooth with regard to structures and properties.