Investigating conformational switching using scanning tunneling microscopy

CHED 188

Christopher M. Pochas, cmp294@psu.edu1, Sanjini U. Nanayakkara, sun110@psu.edu1, Meaghan M. Blake, mmb278@psu.edu1, Paul S. Weiss, stm@psu.edu1, James M. Tour, tour@rice.edu2, Christine McGuiness, clm279@psu.edu3, Orlando Cabarcos, omc2@psu.edu3, Austin Flatt3, and David L. Allara, dla3@psu.edu3. (1) Departments of Chemistry and Physics, The Pennsylvania State University, 104 Davey Laboratory, University Park, PA 16802, (2) Department of Chemistry and Center for Nanoscale Science and Technology, Rice University, 6100 Main, Houston, TX 77005, (3) Department of Chemistry and Materials Research Institute, The Pennsylvania State University, 206 Chemistry Building, University Park, PA 16802
We have observed conductance switching for individual 4-{methyl-[4-(methyl-phenyl-amino)-phenyl]-amino}-benzenethiol (PAPAB) molecules inserted into octanethiolate self-assembled monolayers on Au {111} using scanning tunneling microscopy. Individual PAPAB molecules exhibited an intermediate conductance state between the maximum and minimum states, and showed preferential switch activity at negative tip bias voltages. The bias polarity preference is discussed in terms of the direction of the molecular dipole. Previously, we have shown that conductance switching is a result of a hybridization change at the molecule-substrate interface. In the case of PAPAB molecules, we hypothesize that the intermediate state may be a result of low energy barriers between conformational isomers of the molecule, which are attained by a hybridization change at the tertiary amino groups linking the aromatic rings.
 

Undergraduate Research Poster Session: Analytical Chemistry
2:30 PM-4:30 PM, Monday, 11 September 2006 Moscone Center -- Hall D, Poster

Division of Chemical Education

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006