Role of chain length on the surface chemistry of dienes studiedby scanning tunneling microscopy

The scanning tunneling microscope has been used to observe sites selection of diene molecules on Si(111) 7×7 as a function of their chain length. The molecules 1,6-heptadiene and 1,7-octadiene can chemisorb on either of three geometries on the surface. The different relative affinity of the molecules to these sites is explained by matching between the molecules length and the surface sites. For 1,13-tetradecadiene, each end of the molecule reacts with a different half of the unit cell.