Effects of -NO2 substitution on charge addition and reorganization energies in phenylene ethynylene oligomers
Abstract
Reports of non-linear transport in molecular-scale junctions have stimulated suggestions for computing and switching applications based on molecular electronics. One of the most widely referenced results is reported negative differential resistance (NDR) behavior in -NO2 substituted oligo- phenylene ethynylenes (OPE). Theoretical work has invoked the importance of charge addition effects on conformation and electronic structure and polaronic effects to provide potential explanations for this behavior. We have investigated charge addition effects for pristine versus -NO2 substituted OPE self-assembled monolayers using photoelectron spectroscopy in combination with ``doping'' with K. Results are consistent with differences arising from filling of levels associated with the - NO2 group. We have investigated polaronic effects using photoelectron spectroscopy and optical absorption to guide calculations of reorganization energies for pristine versus -NO2 substituted OPE's. We find theoretical evidence for increased reorganization energy with -NO2 substitution for anionic species by about 33 percent, with experimental values of the reorganization energy ranging from about 0.2 eV to 0.4 eV and theoretical values about 0.2 eV.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 2007
- Bibcode:
- 2007APS..MARB44007R