Ted Pappenfus (Chemistry), and UMM students, Nate Williams, Will Stegner, Jared Johnson, and Brett Edlund. "Optical, Redox, and NLO Properties of Tricyanovinyl Oligothiophenes: Comparisons between Symmetric and Asymmetric Substitution Patterns." In Chemistry - A European Journal , Volume #12 (2006) pp 5358-5470. Wiley, 2006
Abstract: A series of tricyanovinyl (TCV)-substituted oligothiophenes was synthesized and investigated with a number of physical methods including UV/Vis, IR, and Raman spectroscopy, nonlinear optical (NLO) measurements, X-ray diffraction, and cyclic voltammetry. The comparative effects of the symmetric and asymmetric substitutions in the electronic and molecular properties were addressed. To the general reader, this paper combines physical methods with modern theoretical approaches to better understand advanced molecules and materials, which will play a prominent role in many future technologies. This research was a collaborative effort between several institutions. William Stegner and Nathaniel Williams began the project during the Introduction to Research course required of UMM's chemistry majors. Jared Johnson and Brett Edlund participated in this research the summer after their sophomore years. Jared is completing his Spanish major at UMM and Brett is employed in industry. This research was supported through a Grant-in-Aid of Research, Artistry and Scholarship from the Office of the Dean of the Graduate School of the University of Minnesota.
Link(if available): http://www3.interscience.wiley.com/cgi-bin/abstract/112596599/ABSTRACT
Ted Pappenfus, "Exploration of Ground and Excited Electronic States of Aromatic and Quinoid S,S-Dioxide Terthiophenes. Complementary Systems for Enhanced Electronic Organic Materials." In Journal of the American Chemical Society, Volume 128, pp 10134-10144:ACS Publications, 2006
Abstract: Electronic and molecular structures for the ground and excited electronic states of aromatic and quinoid-type oligothiophene sulfones were analyzed. These represent extremes of electron rich and deficient ground states, often exhibiting complementary properties. Oxidizing the central sulfur atom affects the molecular structure, electron affinity, and photophysics of both pi-systems. The consequences for 3T include de-aromatization of the central thiophene, red-shifting of the electronic absorption spectrum, and lowering of the reduction potential. The electron deficient quinoid shows an enhancement of electron affinity from reducing the electron-donor ability of sulfur, and a blue-shifting of its electronic absorption spectrum was seen. A combined theoretical/experimental investigation was presented.
Link(if available): http://pubs.acs.org/cgi-bin/abstract.cgi/jacsat/2006/128/i31/abs/ja061372w.html
Ted Pappenfus, "N- and P-Channel Transport Behavior in Thin Film Transistors Based on Tricyanovinyl-Capped Oligothiophenes," In Journal of Physical Chemistry B, Volume 110, pp 14590-14597: ACS Publications, 2006.
Abstract: Structural and electrical characterization of thin films of organic semiconductor molecules consisting of an oligothiophene core capped with electron-withdrawing tricyanovinyl (TCV) groups are presented. X-ray diffraction and atomic force microscopy of evaporated films of three different TCV-capped oligothiophenes showed that the films were highly crystalline. Electrical transport was measured in thin film transistors employing silver source and drain contacts and channel probes to correct for contact resistance. Overall, these results confirm that substitution of oligothiophene cores with electron-withdrawing groups is a useful strategy to achieve electron-transporting materials.
Link(if available): http://pubs.acs.org/cgi-bin/abstract.cgi/jpcbfk/2006/110/i30/abs/jp061168v.html
Additional publications can be found on the homepage of Ted Pappenfus: http://cda.morris.umn.edu/~pappe001/