The role of buried hydrogen bonds in self-assembled mixed composition thiols on Au{111}

We have investigated the role of internal functionality in self-assembled m onolayers of a family of am amide-containing alkanethiol molecules on Auf{1 11} using scanning tunneling microscopy. In addition to van der Waals inter actions that are present within n-alkanethiol self-assembled monolayers, hy drogen bonding between adjacent buried amide groups contributes to the stab ility of the amide-containing molecules on the surface and causes spontaneo us phase separation upon coadsorption with an n-alkanethiol. A deposition s olution concentration dependence study reveals that this is an observed tre nd across a range of examined solution compositions. Additionally, hydrogen bonding affects the packing structure of the amide-containing alkanethiol self-assembled monolayers. Although they adopt the same (root 3x root3)R30 degrees base lattice as n-alkanethiolate self-assembled monolayers, the ami de-containing molecules form superlattice structures that are more linear t han n-alkanethiol monolayers due to the hydrogen bonds they form. The inter nal functionality of monolayers can be used to control their formation and stability.