Collective Reactivity of Molecular Chains Self-Assembled on a Surface

Abstract

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 CH3S intermediates.

Inducing Nonlocal Reactions with a Local Probe

“…The emerging body of work describing nonlocal reactions induced by the STM suggests exciting new opportunities and directions that will enable improved understanding of organic/inorganic interfaces, with the possible consequence of enhanced device performance in the areas of organic electronics, photonics, and photovoltaics. Hotelectron injection has already been shown to initiate reactions of isolated molecules on metal surfaces, 33,35 in organic thin films, 36 and, now, at metal/organic interfaces formed in molecular monolayers. 34 In addition to providing new insight into the transport properties of metal/organic interfaces, this technique could address the problem of using the STM tip to react relatively large regions of molecules spontaneously and simultaneously.…”

“…This lateral extent can be augmented through the controlled use of a chain reaction. In their most recent work, Maksymovych et al 33 combined the nonlocal reactivity induced by hot electrons with the chemical chain reaction responsible for sequentially dissociating and re-forming CH 3 SSCH 3 molecules. By applying a voltage pulse to the bare substrate, they induced the chain reaction in molecular chains in the surrounding region.…”

“…A different type of linearly propagating chain reaction induced by the STM tip was recently demonstrated by Maksymovych and coworkers. 33 In this system, chains of dimethyldisulfide (CH 3 SSCH 3 ) mol- Figure 1). 34 After propagating laterally, some proportion of the hot electrons back-transfer into molecular orbitals, inducing chemical reactions at distances up to 12 nm from the STM tip.…”

Electron Transport through Cyclic Disulfide Molecular Junctions with Two Different Adsorption States at the Contact: A Density Functional Theory Study

“…[32][33][34][35] Indeed, the irreversible oxidation peak at 0.90 V observed for alkanetetrathiols is attributed to oxidation of thiol groups, leading to the formation of disulfide linkages. 36 It was also reported that dissociation of dimethyl disulfide (CH 3 SSCH 3 ) adsorbed on the Au(111) surface can be accomplished by applying a voltage of ∼1.4 V. 37 Existence of disulfide bonds has long been a controversy for alkanethiols and dialkyl disulfides adsorbed on gold surfaces. [37][38][39][40][41][42][43][44][45] Thus, we posed the following questions: What if the application of the bias voltage induces the formation or breakage of the disulfide bonds of 1?…”

Hydrogen Oxidation-Driven Hot Electron Flow Detected by Catalytic Nanodiodes

“…A few chemical processes on high work-function metal surfaces have been recently discovered that transfer a substantial fraction of the reaction heat to the kinetic energy of individual metal electrons [1][2][3][4][5][6][7][8][9][10][11][12] . There is growing evidence which indicates that these energetic electrons, often called hot electrons, influence surface reactivity 13,14 . These energetic subsurface electrons have been directly detected in metal/semiconductor Schottky diodes whose metal surface is subject to a chemical process 15, 16 , 17 .…”