Exploring self-assembly in functionalized acenes

Silylethyne substitution is a versatile approach to control solubility and crystalline order in high aspect ratio chromophores such as acenes. We have developed some simple rules to predict crystal packing in such substituted systems, and these rules were more recently refined by careful computational analysis. We also found that trialkylgermylethynyl-substituted acenes and heteroacenes followed nearly identical rules to the silyl derivatives. Due to their lower cost and more versatile synthetic variability, we have now begun to prepare trialkyl-carbon substituted alkynes to use in the crystal engineering of acenes and heteroacenes. We were rather surprised to discover that these carbon-based systems did not follow the same rules for packing as the silyl or germyl alkynes. We will present a systematic study of acene crystal packing in relation to several classes of carbon-based alkyne systems, the low-cost, scalable syntheses of these alkynes, computational assessment of the resulting crystal packings, and FET studies of select materials. We have also expanded the dimensionality of the backbones under study by incorporating pyrene units - the impact of pyrene insertion on the electronic structure of acenes will be covered in detail.