Electrons are transported through phenylene-ethynylene oligomer monolayers via localized molecular orbitals.
We report excellent correlations between the first negative threshold potentials (V(TH)s) for electric conduction, electrochemical potentials, and computed lowest unoccupied molecular orbital energies in a series of phenylene-ethynylene oligomers bearing a sulfur-based anchoring unit and different electroactive substituents on the central benzene ring. The theoretical and electrochemical results strongly suggest that the peaks observed in the i-V curves have a true molecular origin and are associated with distinct unoccupied molecular levels of the compounds that are strongly localized on the central ring (except for compound I). This localization might account for the existence of a long-lived radical-anion state that permits lateral electron hopping and leads to charge trapping and storage.
Department of Chemistry and Biochemistry and Center for Nano- and Molecular Science, The University of Texas at Austin, Austin, Texas 78712, uSA.
Fu-Ren F
FR
Fan
Rebecca Y
RY
Lai
Jérôme
J
Cornil
Yasser
Y
Karzazi
Jean-Luc
JL
Brédas
Lintao
L
Cai
Long
L
Cheng
Yuxing
Y
Yao
David W
DW
Price
Shawn M
SM
Dirk
James M
JM
Tour
Allen J
AJ
Bard