Epitaxial Supramolecular Assembly of Fullerenes Formed by Using a Coronene Template on a Au(111) Surface in Solution

Characteristic properties of the coronene layer formed on Au(111) for the epitaxial growth of various fullerenes are described. The electrochemical behavior of the coronene adlayer prepared by immersing a Au(111) substrate into a benzene solution containing coronene was investigated in 0.1 M HClO₄. The as-prepared coronene adlayer on Au(111) revealed a well-defined (4 × 4) structure. Structural changes of the array of coronene molecules induced by potential manipulation were clearly observed by in situ scanning tunneling microscopy (STM). Supramolecularly assembled layers of fullerenes such as C₆₀, C₇₀, C₆₀−C₆₀ dumbbell dimer (C₁₂₀), C₆₀−C₇₀ cross-dimer (C₁₃₀), and C₆₀ triangle trimer (C₁₈₀) were formed on the well-defined coronene adlayer on the Au(111) surface by immersing the coronene-adsorbed Au(111) substrate into benzene solutions containing those molecules. The adlayers thus prepared were characterized by comparison with those which were directly attached to the Au(111) surface. The C₆₀ molecules formed a honeycomb array with an internal structure in each C₆₀ cage on the coronene adlayer, whereas C₇₀ molecules were one-dimensionally arranged with the same orientations. The dimers, C₁₂₀ and C₁₃₀ molecules, formed an identical structure with c(11 × 4√3)rect symmetry. For the C₁₃₀ cross-dimer molecule, C₆₀ and C₇₀ cages were clearly recognized at the molecular level. It was difficult to identify the adlayer of the C₁₈₀ molecule directly attached to Au(111); however, individual C₁₈₀ molecules could be recognized on the coronene-modified Au(111) surface. Thus, the adlayer structures of those fullerenes were strongly influenced by the underlying coronene adlayer, suggesting that the insertion of a coronene adlayer plays an important role in the formation of supramolecular assemblies of fullerenes.