title: Single-electron induces double-reaction by charge delocalization.
abstract: Injecting an electron by scanning tunneling microscope into a molecule physisorbed at a surface can induce dissociative reaction of one adsorbate bond. Here we show experimentally that a single low-energy electron incident on ortho-diiodobenzene physisorbed on Cu(110) preferentially induces reaction of both of the C-I bonds in the adsorbate, with an order-of-magnitude greater efficiency than for comparable cases of single bond breaking. A two-electronic-state model was used to follow the dynamics, first on an anionic potential-energy surface (pes*) and subsequently on the ground state pes. The model led to the conclusion that the two-bond reaction was due to the delocalization of added charge between adjacent halogen-atoms of ortho-diiodobenzene through overlapping antibonding orbitals, in contrast to the cases of para-dihalobenzenes, studied earlier, for which electron-induced reaction severed exclusively a single carbon-halogen bond. The finding that charge delocalization within a single molecule can readily cause concerted two-bond breaking suggests the more general possibility of intra- and also intermolecular charge delocalization resulting in multisite reaction. Intermolecular charge delocalization has recently been proposed by this laboratory to account for reaction in physisorbed molecular chains (Ning, Z.; Polanyi, J. C. Angew. Chem., Int. Ed. 2013, 52, 320-324).
authors.affiliation: Lash Miller Chemical Laboratories, Department of Chemistry and Institute of Optical Sciences, University of Toronto, 80 St. George Street, Toronto, Ontario, M5S 3H6 Canada.
authors.forename: Kai
authors.initials: K
authors.lastname: Huang
authors.forename: Lydie
authors.initials: L
authors.lastname: Leung
authors.forename: Tingbin
authors.initials: T
authors.lastname: Lim
authors.forename: Zhanyu
authors.initials: Z
authors.lastname: Ning
authors.forename: John C
authors.initials: JC
authors.lastname: Polanyi