[Aspuru-Guzik Group List] Group meeting, Thu Mar 22, 3:30 PM, Div Room

Hi all, Tomorrow Dennis will speak at group meeting. See below for his title and abstract. Best, Ian ----------------- Title: Charge π-Delocalization in Oligofurans Abstract: I will present my previous work in the field of organic electronics that was done in Weizmann Institute of Science, Israel. The group of Michael Bendikov introduced a new family of conjugated organic electronic materials, a-oligofurans. Oligofurans exhibit higher fluorescence, better packing, greater rigidity, and higher solubility than the corresponding oligothiophenes. Additionally, oligofurans display good electronic properties, e.g., field effect mobilities and on-off ratios, similar to those of the corresponding oligothiophene analogues. One-electron oxidation of the oligofurans produces well-defined cation radicals, which can serve as a model for the lightly–moderately doped state of the corresponding conjugated polymers. I will present an experimental (EPR, Vis-UV-NIR) and computational (DFT, ab-initio) study of the cation radicals of long oligofurans. I will present results on a charge π-delocalization (i.e., polaron) from experiment and calculations. Several experimental techniques were employed to study the delocalization of polaron in conjugated oligomers and polymers and to estimate its delocalization length. However, these methods are indirect and use complicated analysis and assumptions. Here we perform a direct study of the π-delocalization by EPR spectroscopy on oligofuran cation radicals with increasing chain length as a model for π-conjugated 5-member-heterocycle based polymers (e.g., polythiophene). EPR spectroscopy can provide us with direct estimation of spin density on each atom (from which we can learn about delocalization length) through hyperfine coupling constants (HFCC).