A versatile cross-coupling/cyclization methodology for the synthesis of fused polycyclic aromatics: Application to molecular and polymeric systems

The research reported herein describes synthetic and physical investigations into molecular and polymeric conjugated organic systems; more specifically fused polycyclic aromatic systems. Central to this work was the use of Pd catalyzed cross-coupling chemistry which allowed for the ready construction of a variety of conjugated frameworks. Also critical to this work was the development of an electrophile-induced cyclization reaction which utilizes electron-rich triple bonds. The cyclization, which often proceeds in very high to quantitative yields, constitutes one of only very few direct routes into fused polycyclic systems. Chapter 2 describes the development of this cyclization reaction and describes the all-carbon and heterocyclic systems which have been prepared using the reaction. In addition, the results of studies aimed at elucidating the mechanism will be discussed. The preparation of all-carbon fused polycyclic aromatic polymers or graphite ribbons, the ultimate goal of this research, is described in Chapter 3. Also described are the results of studies performed on substituted pentaphenylene systems which serve as more extended models of the polymer systems. The goal of these studies was to determine the degree to which the polymer or graphite ribbon systems contained structural irregularities. The use of photoluminesence spectroscopy proved invaluable in these studies and serves as a sensitive probe of structural defects. This sensitivity is derived from the extended conjugated nature of these systems which allows for energy migration over long distances and hence permits efficient sampling of the electronic systems of these materials. The conscious exploitation of this property by carefully choosing defect sites allows for the preparation of materials which may be used as sensory materials. Chapter 4 describes such a system which uses host-guest interactions to provide the structural irregularity. The synthesis and unusual photophysical properties of a calixarene functionalized poly(phenylenebithiophene) which selectively binds Na$\sp+$ over K$\sp+$ and Li$\sp+$ ions is described. The observation of a digital or on/off photoluminescent response is also described