title: Local electronic and chemical structure of oligo-acetylene derivatives formed through radical cyclizations at a surface.
abstract: Semiconducting π-conjugated polymers have attracted significant interest for applications in light-emitting diodes, field-effect transistors, photovoltaics, and nonlinear optoelectronic devices. Central to the success of these functional organic materials is the facile tunability of their electrical, optical, and magnetic properties along with easy processability and the outstanding mechanical properties associated with polymeric structures. In this work we characterize the chemical and electronic structure of individual chains of oligo-(E)-1,1'-bi(indenylidene), a polyacetylene derivative that we have obtained through cooperative C1-C5 thermal enediyne cyclizations on Au(111) surfaces followed by a step-growth polymerization of the (E)-1,1'-bi(indenylidene) diradical intermediates. We have determined the combined structural and electronic properties of this class of oligomers by characterizing the atomically precise chemical structure of individual monomer building blocks and oligomer chains (via noncontact atomic force microscopy (nc-AFM)), as well as by imaging their localized and extended molecular orbitals (via scanning tunneling microscopy and spectroscopy (STM/STS)). Our combined structural and electronic measurements reveal that the energy associated with extended π-conjugated states in these oligomers is significantly lower than the energy of the corresponding localized monomer orbitals, consistent with theoretical predictions.
authors.affiliation: Department of Physics, University of California , Berkeley, California 94720, United States.
authors.forename: Alexander
authors.initials: A
authors.lastname: Riss
authors.forename: Sebastian
authors.initials: S
authors.lastname: Wickenburg
authors.forename: Patrick
authors.initials: P
authors.lastname: Gorman
authors.forename: Liang Z
authors.initials: LZ
authors.lastname: Tan
authors.forename: Hsin-Zon
authors.initials: HZ
authors.lastname: Tsai
authors.forename: Dimas G
authors.initials: DG
authors.lastname: de Oteyza
authors.forename: Yen-Chia
authors.initials: YC
authors.lastname: Chen
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Bradley
authors.forename: Miguel M
authors.initials: MM
authors.lastname: Ugeda
authors.forename: Grisha
authors.initials: G
authors.lastname: Etkin
authors.forename: Steven G
authors.initials: SG
authors.lastname: Louie
authors.forename: Felix R
authors.initials: FR
authors.lastname: Fischer
authors.forename: Michael F
authors.initials: MF
authors.lastname: Crommie