Aurophilicity

In chemistry, aurophilicity refers to the apparent tendency of gold complexes to aggregate via formation of weak gold-gold bonds. The phenomenon is most commonly observed crystallographically for Au(I) compounds. The aurophilic bond has a length of about 3.0 Å and a strength of about 7-12 kcal/mol, which is comparable to the strength of a hydrogen bond. The aurophilic interaction is considered to result from electron correlation of the closed-shell components, somewhat similar to van der Waals interactions, but unusually strong due to relativistic effects. Other heavy metals display a similar tendency to aggregate, especially in the solid state.