Collective reactivity of molecular chains self-assembled on a surface

Self-assembly of molecules on surfaces is a route toward not only creating structures, but also engineering chemical reactivity afforded by the intermolecular interactions. Dimethyldisulfide (CH₃SSCH₃) molecules self-assemble into linear chains on single-crystal gold surfaces. Injecting low-energy electrons into individual molecules in the self-assembled structures with the tip of a scanning tunneling microscope led to a propagating chemical reaction along the molecular chain as sulfur-sulfur bonds were broken and then reformed to produce new CH₃SSCH₃ molecules. Theoretical and experimental evidence supports a mechanism involving electron attachment followed by dissociation of a CH₃SSCH₃ molecule and initiation of a chain reaction by one or both of the resulting CH ₃S intermediates.