1 research outputs found
Local Electronic and Chemical Structure of Oligo-acetylene Derivatives Formed Through Radical Cyclizations at a Surface
Semiconducting
Ï€-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-(<i>E</i>)-1,1′-biÂ(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
(<i>E</i>)-1,1′-biÂ(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