How Adsorbate Alignment Leads to Selective Reaction

Abstract

There has been much interest in the effect of adsorbate alignment in a surface reaction. Here we show its significance for an electron-induced reaction occurring along preferred axes of the asymmetric Cu(110) surface, characterized by directional copper rows. By scanning tunneling microscopy (STM), we found that the heterocyclic aromatic reagent, physisorbed meta-iodopyridine, lay with its carbon-iodine either along the rows of Cu(110), "A", or perpendicular, "P". Electron-induced dissociative attachment with the C-I bond initially along "A" gave a chemisorbed I atom and chemisorbed vertical pyridyl, singly surface-bound, whereas that with C-I along "P" gave a chemisorbed I atom and a horizontal pyridyl, doubly bound. An impulsive two-state model, involving a short-lived antibonding state of C-I, accounted for the different product surface binding in terms of closer Cu···Cu atomic spacing along "A" accommodating only one binding site of the pyridyl ring recoiling from I and wider spacing along "P" accommodating simultaneously both binding sites, N-Cu and C-Cu, in the meta-position on the recoiling pyridyl ring. STM studies combined with dynamical modeling can be seen as a way to improve understanding of the role of surface alignment in determining reactive outcomes in induced reaction at asymmetric crystalline surfaces.

Correlation of interfacial bonding mechanism and equilibrium conductance of molecular junctions

“…We speculate that these two bonding configurations are switchable between each other by changing the local chemical environment, e.g. local geometry [37], at the interface, so that the electric conductance is thus, most likely, tunable by the interfacial environment. Our investigation reveals how the interfacial geometry correlates with the interfacial bonding configuration and could drastically influence transport properties.…”

Halogen and structure sensitivity of halobenzene adsorption on copper surfaces

“…1 Predicting reaction efficiencies in the two-dimensional confinement on surfaces thus demands a thorough knowledge about the adsorption orientations of the participating molecules. 2,3 This should be particularly true for the emerging field of on-surface synthesis on metal surfaces, which investigates individually synthesised molecules by scanning tunneling microscopy. 4,5 The first 6,7 and still most prominently employed 8,9 path in on-surface synthesis uses Ullmann-like coupling, 10 a C-C-coupling from halogenated molecules on the coinage metal surfaces.…”

Benzene derivatives adsorbed to the Ag(111) surface: Binding sites and electronic structure

“…Moreover, it has recently been shown that the relative alignment of the substrate and adsorbate atoms can influence reaction pathways and products. 40 Thus, a number of design parameters can be utilized to engineer structures with specific properties.…”