Substituent-Dependent Ordering of Adlayer Structures of Fullerene Derivatives Adsorbed on Au(111): A Scanning Tunneling Microscopy Study

Abstract

The adsorption of four fullerene derivatives, including Re(C60Me5)(CO)3, Ru(C60Ph5)Cp, C60(C6H4C6H4−COOH)5Me, and C60(C6H4−CC−SiMe2C12H25)5Me, on a Au(111) surface has been investigated by scanning tunneling microscopy (STM) and cyclic voltammetry. High-resolution STM images reveal that Re(C60Me5)(CO)3 forms a well-ordered (2√3 × 2√3)R30° structure. Different from C60 on Au(111), the so-called “in-phase” structure is not found with the attachment of methyl and Re(CO)3 groups. With the increase of substituent size, disordered adlayers have been observed for Ru(C60Ph5)Cp and C60(C6H4C6H4−COOH)5Me. However, the individual molecules could be distinguished in STM images, suggesting that the two molecules interact strongly with the Au(111) surface. When the substituent size is further increased, a multilayered structure is formed for C60(C6H4−CC−SiMe2C12H25)5Me. This is because of molecular aggregation in the bulk solution, which occurs at very low concentration. These results indicate that the structures of fu...