Interfacial structures of self-assembled monolayers of 2-pyridinethiol on Au(111) studied by in situ scanning tunneling microscopy

In situ Scanning Tunneling Microscopy (STM) operating under electrochemical condition was used to study self-assembled monolayers of 2-pyridinethiol (2-PySH) on Au(111) in perchloric acid solution. Each molecule appeared as two spots, presumably originated from adsorption through S and N atoms of 2-pyridinethiolate with a vertical orientation on the Au(111) surface. The ordered 2-pyridinethiolate monolayers exhibited a p(4 x √7R-40.9deg) structure, which was constructed by alternative arrangements of two types of molecular rows with differently rotated molecules. In situ STM also revealed that the monolayer consisted of molecularly ordered domains with the p(4 x √7R-40.9deg) structure, its mirror structure defined as a p(4 x √7R-19.1deg), and their rotational structures. Detailed interfacial structures and molecularly ordered domains of the 2-pyridinethiolate monolayer have been elucidated by in situ STM imaging in aqueous solution. (author)