The synthesis of larger acene-like molecules (heteroacenes) is planned. In the heteroacenes, some of the aromatic C-H groups are substituted by pyridine-type nitrogens. The groups will probe the influence of an increasing number of nitrogen ring atoms on the optical, electrochemical and electrical properties of the heteroacenes. To increase the solubility (of the proposed acene-types) and enforce mutual overlap of the aromatic molecules in the solid state,they will install (trialkylsilyl)ethynyl groups as substituents. The trialkylsilyl groups facilitate the solution-phase processing of the heteroacenes. The synthesis part will be expanded towards halogenated azapentacenes as these are of great current interest as electron transport materials and can be made readily by intermediates that are prepared en route. A broad investigation of the thin film formation of the heteroacenes on solid supports is planned. These thin films will be examined by microscopy and spectroscopic methods; the groups plan to modify the underlying surfaces by organic ligands to control the stacking and packing of the proposed heteroacenes to optimize their electric properties parallel and perpendicular to the surface and envision potential applications in organic electronics. The proposed heteroacenes are electron conducting materials for n-channel thin film transistors. The heteroacenes should have similar electric properties to pentacene (the most important organic semiconductor). They can transport electrons instead of positive charges (holes). Heteroacenes potentially allow the construction of organic electronic devices with reverse polarity and reverse flow of current. Such reversed-polarity thin film transistors are of broad importance as drivers in advanced light emitting diodes and solid-state lighting devices. The PI has established a track record for working with minority high schools and has taught an advanced organic chemistry class at an HBCU (Clark Atlanta). It is planned to continue these activities during this grant period.
