Date of Award
Program or Major
Master of Science
Glen P Miller
Two new monosubstituted pentacene derivatives, 6-phenylthiopentacene, 26, and 6-acetylthiopentacene, 27, have been prepared using a dehydrogenative aromatization and elimination reaction that utilizes 1,8-diazabicycloundec-7-ene (DBU) as reagent. Although many disubstituted pentacenes have been synthesized and characterized, monosubstituted pentacenes have received much less attention. While studying the photodegradation of 26 under ambient light and air conditions, an unexpected transformation to 6,13-bis(phenylthio)pentacene, 32, was observed. The transformation requires short wavelength (254 nm) UV irradiation. Through a combined experimental and computational study, we have identified this transformation as a multi-step intramolecular process initiated by the photoexcitation of the endo anti dimer of 26. The photoexcited dimer undergoes an intramolecular acid-base reaction which involves two proton transfers and nucleophilic substitution to form the rearranged photodimer which upon dissociation yields bisadduct 32. Using 254 nm light and a quartz reaction vessel, bisadduct 32 has been isolated in 20% yield from monoadduct 26.
Chan, Julia Y K, "Synthesis of 6-thiosubstituted pentacenes and study of an unexpected photorearrangement of 6-phenylthiopentacene dimer" (2011). Master's Theses and Capstones. 678.