Novel conjugated materials via zirconocene coupling and palladium-catalyzed cross-coupling.

摘要

Organic electronic materials are viable competitors for next-generation solar cells, display technology, and sensors. Progress in this field is driven by collaborative feedback between chemists, who make materials, and engineers, who optimize device performance. This dissertation focuses on two methods for synthesizing new conjugated materials: zirconocene coupling and palladium-catalyzed cross-coupling. Chapters 1 and 2 investigate the synthesis and reactivity of an electron-deficient building block for n-type organic semiconductors. Chapter 3 explores beta-directing groups for zirconocene coupling, while Chapter 4 describes the diastereoselective macrocyclization of 1,4-bis[(trimethylsilyl)ethynyl]acenes.;In Chapter 1, 9,10-dichlorooctafluoroanthracene is synthesized from commercially available tetrafluorophthalic acid by an optimized solution-phase route. Stirring 9,10-dichlorooctafluoroanthracene with phenylboronic acid under modified Suzuki-Miyaura coupling conditions generates octafluoro-9,10-diphenylanthracene in high yield. Cyclic voltammetry and X-ray crystallography indicate that octafluoro-9,10-diphenylanthracene has a stabilized LUMO energy level and extended pi stacking, which should lead to efficient electron transport in solid-state devices.;Further coupling chemistry with 9,10-dichlorooctafluoroanthracene is examined in Chapter 2. It reacts with aryl boronic acids and terminal alkynes under palladium-catalyzed cross-coupling conditions to afford 9,10-diaryloctafluoroanthracenes and 9,10-dialkynyloctafluoroanthracenes, respectively. Optical spectroscopy and cyclic voltammetry indicate that octafluoro-9,10-di(thiophen-2-yl)anthracene exhibits donor-acceptor character and a LUMO energy level of --3.27 eV relative to vacuum. X-ray crystallographic analysis of octafluoro-9,10-bis[(trimethylsilyl)ethynyl]anthracene reveals a solid-state structure that mimics the packing of columnar liquid crystals, with a pi stacking distance of 3.39 A between the octafluoroanthracene cores. In addition, octafluoro-9,10-bis(mesitylethynyl)anthracene displays a LUMO energy level of --3.50 eV, which approaches the value of --3.65 eV measured for perfluoropentacene, making 9,10-dialkynyloctafluoroanthracenes a promising new class of n-type organic semiconductors.;Chapter 3 investigates the zirconocene-mediated coupling of o-methyl-substituted (phenylethynyl)benzenes. Coupling of 1,3,5-trimethy1-2-(phenylethynyl)benzene and 1,3-dimethy1-2-(phenylethynyl)benzene is completely regioselective, giving the betabeta stereoisomer in excellent yield. The regioselectivity appears to be directed by steric bulk at the alkyne, as 1-methyl-2-(phenylethynyl)benzene affords 88% conversion to the betabeta product, while zirconocene coupling of 1,3-dimethy1-5-(phenylethynyl)benzene and 1-methyl-3-(phenylethynyl)benzene display no selectivity. Zirconocene coupling of the mesityl-containing alkyne, 1,3,5-trimethy1-2-(phenylethynyl)benzene, is readily reversible, and the zirconacyclopentadiene product undergoes substitution reactions with 3-hexyne and diphenylacetylene. Furthermore, the mesityl-substituted zirconacycle can be transformed into a butadiene or thiophene oxide by reaction with benzoic acid or sulfur dioxide, respectively. These conjugated units are difficult to synthesize by other methods, making the regioselective and reversible zirconocene-mediated coupling of mesityl-substituted alkynes a viable route to new materials.;Finally, Chapter 4 centers on the synthesis of novel macrocycles and cyclophanes. Although there are two possible diastereomeric products, zirconocene-mediated trimerization of 1,4-bis[(trimethylsilyl)ethynyl]acenes is stereoselective, generating only the energetically-favored "2 up, 1 down" isomer. Improved understanding of the factors governing stereoselective macrocyclizations will enable new supramolecular building blocks for a variety of applications.