title: Importance of direct metal-π coupling in electronic transport through conjugated single-molecule junctions.
abstract: We study the effects of molecular structure on the electronic transport and mechanical stability of single-molecule junctions formed with Au point contacts. Two types of linear conjugated molecular wires are compared: those functionalized with methylsulfide or amine aurophilic groups at (1) both or (2) only one of its phenyl termini. Using scanning tunneling and atomic force microscope break-junction techniques, the conductance of mono- and difunctionalized molecular wires and its dependence on junction elongation and rupture forces were studied. Charge transport through monofunctionalized wires is observed when the molecular bridge is coupled through a S-Au donor-acceptor bond on one end and a relatively weak Au-π interaction on the other end. For monofunctionalized molecular wires, junctions can be mechanically stabilized by installing a second aurophilic group at the meta position that, however, does not in itself contribute to a new conduction pathway. These results reveal the important interplay between electronic coupling through metal-π interactions and quantum mechanical effects introduced by chemical substitution on the conjugated system. This study affords a strategy to deterministically tune the electrical and mechanical properties through molecular wires.
authors.affiliation: Department of Chemistry, Columbia University, New York, New York 10027, United States.
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Meisner
authors.forename: Seokhoon
authors.initials: S
authors.lastname: Ahn
authors.forename: Sriharsha V
authors.initials: SV
authors.lastname: Aradhya
authors.forename: Markrete
authors.initials: M
authors.lastname: Krikorian
authors.forename: Radha
authors.initials: R
authors.lastname: Parameswaran
authors.forename: Michael
authors.initials: M
authors.lastname: Steigerwald
authors.forename: Latha
authors.initials: L
authors.lastname: Venkataraman
authors.forename: Colin
authors.initials: C
authors.lastname: Nuckolls