Hydrogenation of nanostructured carbon, synthesis of organic semiconductors and progress towards synthesis of fullerenes and nanoribbons from polyaromatic hydrocarbons
The hydrogenation of carbon allotropes including fullerenes, nanotubes and graphene was investigated using polyamines as hydrogenation reagents. In each case, a rapid, scalable and reversible hydrogenation was observed. The mechanism of hydrogenation was explored using several different polyamines. It was shown that a two-carbon spacer between amine groups is critical for efficient hydrogenation, as well as the presence of at least two adjacent amines that are not tertiary. The extent of hydrogenation on the fullerenes is a function of reaction temperature. C3nuC 60H18 forms preferentially at approximately 200 °C whereas C60H36 species are preferentially formed at approximately 340 °C and above. S6C60H24 was found to be produced in small quantities whenever fulleranes were produced. Despite attempts to isolate S6C 60H24 by HPLC chromatography, only a few milligrams could be obtained. The material was shown to be particularly insoluble in its purified form making detailed spectroscopic analysis difficult. The synthesis of acenes, bisacenes and periacenes was accomplished. Unsubstituted bipentacene was successfully synthesized for the first time and showed improved solubility compared to pentacene. Peripentacenequinone was also synthesized, a stable organic semiconductor that exhibits poor solubility. A new type of organic semiconductor, trithiapentacenone (TTPO), was also synthesized. TTPO exhibits superior thermal and photooxidative stability, and is in fact stable in air at 400 °C. The distribution of charge in TTPO promotes crystallization with a head-to-tail stacking arrangement that promotes parallel displaced columnar stacks. TTPO shows variable temperature transistor behavior with higher mobilities at higher temperatures. Exploration into the formation of graphene nanoribbons from small molecules (bottom-up synthesis) was explored. By thermal annealing of substituted and unsubstituted pentacenes, large polymeric systems akin to nanoribbons were produced. Using similar methods, a bottom-up synthesis of [60]fullerene was explored and the rapid, efficient synthesis of several precursors including decacyclene was accomplished.
Chemistry, Organic, Nanoscience, Engineering, Materials Science
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