Coadsorption of 2-mercaptopyrimidine and 2,2 '-bipyridine on Au(111) studied by scanning tunneling microscopy

Scanning tunneling microscopy (STM) was employed to study the self-assembly of a single layer of 2,2'-bipyridine (22bpy) and also its coadsorption wit h 2-mercaptopyrimidine (2MPy) on Au(111). STM shows that 22bpy binds on Au( 111) vertically through the nitrogen atoms. There is adsorbate-adsorbate in teraction in the form of pi-stacking. This interaction leads to the formati on of long molecular chains on the surface. The mixed layer of 2MPy and 22b py on Au(111) is a planar structure. The adsorption mode is very similar to the single layer of 2MPy. The 22bpy molecules lie flat and are attached to one edge of the 2MPy dimer. The 2MPy-22bpy mixed layer is compared to the 2MPy-phen layer. (C) 1999 Published by Elsevier Science B.V. All rights res erved.