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 x 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 C-60, C-70, C-60-C-60 dumbbell dimer (C-120), C-60-C-70 cross-dimer (C-130), and C-60 triangle trimer (C-180) 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 C-60 molecules formed a honeycomb array with an internal structure in each C-60 cage on the coronene adlayer, whereas C-70 molecules were one-dimensionally arranged with the same orientations. The dimers, C-120 and C-130 molecules, formed an identical structure with c(11 x 4 root 3)rect symmetry. For the C-130 cross-dimer molecule, C-60 and C-70 cages were clearly recognized at the molecular level. It was difficult to identify the adlayer of the C-180 molecule directly attached to Au(111); however, individual C-180 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.