Polymorphic, Porous, and Host–Guest Nanostructures Directed by Monolayer–Substrate Interactions: Epitaxial Self-Assembly Study of Cyclic Trinuclear Au(I) Complexes on HOPG at the Solution–Solid Interface

Abstract

Synthesis, crystallographic characterization, and molecular self-assembly of two novel cyclotrimeric gold(I) complexes, Au3[3,5-(COOEt)2Pz]3 (Au3Pz3) and Au3[(n-Pr–O)C═N(Me)]3 (Au3Cb3) was studied. Single crystal X-ray crystallography data reveal that both gold(I) complexes have one-dimensional stacking patterns caused by intermolecular Au(I)···Au(I) aurophilic interactions. The Au3Pz3 trimer units stack with two alternate and symmetrical Au(I)···Au(I) interactions while the Au3Cb3 units have three alternating and nonsymmetrical Au(I)···Au(I) interactions. Molecular self-assembly of the gold(I) complexes on the 1-phenyloctane/highly ordered pyrolytic graphite (HOPG) (0001) solution–solid interface is studied with scanning tunneling microscopy (STM). The gold(I) cyclotrimers form epitaxial nanostructures on the HOPG surface. At a concentration of ∼1 × 10–4 M, Au3Pz3 complexes exhibit a single morphology, while Au3Cb3 complexes exhibit polymorphology. Two polymorphs, one nonporous and the other porous, are ...