Self-assembled monolayers of aromatic thiols stabilized by parallel-displaced pi-pi stacking interactions.
Parallel-displaced pi-pi stacking interactions have been known to be the dominant force in stabilizing the double helical structure of DNA and the tertiary structure of proteins. However, little is known about their roles in self-assembled monolayers of other large pi molecules such as aromatic thiols. Here we report on a systematic study of the self-assembled monolayers of four kinds of anthracene-based thiols, 9-mercaptoanthracene (MA), (4-mercaptophenyl) (9-anthryl) acetylene (MPAA), (4-mercaptophenyl) (10-nitro-9-anthryl) acetylene (MPNAA), and (4-mercaptophenyl) (10-carboxyl-9-anthryl) acetylene (MPCAA) on Au(111), in which a spacer and different functional groups (NO2 and COOH) are intentionally designed to introduce and thus allow the investigation of various intermolecular interactions, in addition to pi-pi interactions in the base molecules. We find that all molecules form long-range-ordered monolayers and, more interestingly, that these assembled monolayers exhibit essentially the same fundamental packing structure. On the basis of high-resolution scanning tunneling microscopy observations, we propose the space-filling models for the observed superstructures and demonstrate that all superstructures can be understood in terms of the parallel-displaced pi-pi stacking interactions, despite the presence of competing dipole-dipole and H-bonding interactions associated with these specially designed functional groups.
Dou
Rui-Fen
RF
Department of Physics and Materials Science and Technology Research Centre, The Chinese University of Hong Kong, Shatin, Hong Kong, China.
Ma
Xu-Cun
XC
Xi
Luan
L
Yip
Hin Lap
HL
Wong
King Young
KY
Lau
Woon Ming
WM
Jia
Jin-Feng
JF
Xue
Qi-Kun
QK
Yang
Wei-Sheng
WS
Ma
Hong
H
Jen
Alex K-Y
AK