Interaction of 2-mercaptopyrimidine and 4,4 '-bipyridine and competition experiments between bipyridines and 1,10 '-phenanthroline for the thiol layer on Au(111) by STM

STM was employed to study the coadsorption of 4.4'-bipyridine (4bipy) and 2 -mercaptopyrimidine (2MPy) on Au(1 1 1). The adsorption of 4bipy as a singl e layer was also analyzed. For the single layer STM reveals a molecular str ucture made of parallel periodic chains with a repeat distance of 11.5-11.7 Angstrom. The mixed layer is formed with a ratio of two molecules of 2Mpy to one of 4bipy. 4bipy assumes two different positions in relation to the 2 MPy dimer. Competition between 4bipy, 2,2'-bipyridine and 1,10'-phenanthrol ine was investigated to obtain a qualitative view of the preference of the: 2MPy assembly for these molecules. The mixed layers were grown on Au(1 1 1 ) from ternary molecular solutions containing either 2MPy + 4bipy + 2bipy o r 2MPy + 4bipy + phen. STM shows that the resulting layers are made of the 2MPy dimeric assembly plus one of the oligopyridines. A split of the 2MPy d imer or the formation of mixed domains with the: three molecules present in the stock solution was not found. (C) 2001 Elsevier Science B.V. All right s reserved.