Binding between Carbon and the Au(111) Surface and What Makes It Different from the S-Au(111) Bond

In contrast with the case of thiols, molecular level information regarding the binding of carbon to metals is very scarce. Motivated by the growing interest in the grafting of conducting surfaces and seeking a rationale to explain the differences in electron transfer rates measured in recent experiments, we apply density functional theory to shed light on the binding of carbon to gold. A comparative study between the C-Au(111) and the S-Au(111) bonds allows us to establish a thermodynamic, structural, and electronic description of the aromatic and aliphatic chemisorption. Enlightening insight emerges from the projected density of states, which delivers a natural interpretation of the difference in conductance observed for the two kind of linkages.