p ® p* or n ® p* ?: The photophysical characterization of thieno[3,4-b]pyrazine and its 2,3-difunctionalized analogues

ORGN 318

Seth C. Rasmussen, Daniel J. Sattler, Kari A. Mitchell, and John Maxwell. Department of Chemistry, North Dakota State University, Fargo, ND 58105
In order for materials chemists to develop improved electronic materials, it is critically important to understand the various structure-function relationships involved. In polymeric products, this can only be accomplished by fully understanding the same relationships in the monomeric precursors. Unfortunately, there is often little reported electronic and spectroscopic data for the monomeric species making it difficult to predict general relationships. For example, while poly(isothianaphthene) has been extensively studied, the systematic photophysical characterization of the monomeric isothianaphthene is quite limited. In an attempt to better understand the structure-function relationships in polythieno[3,4-b]pyrazine systems, we report herein the photophysical study of thieno[3,4-b]pyrazine and its 2,3-difunctionalized analogues. Full characterization of the room temperature UV-vis and fluorescence spectra, including solvent and pH dependence, are presented and compared to the related species isothianaphthene and quinoxaline. In particular, the nature of the lowest energy transition is thoroughly discussed.