Dithiafulvenyl functional pi-conjugated oligomers and polymers: synthesis, characterization, and applications

Khademabolfazli, Mohammadreza (2017) Dithiafulvenyl functional pi-conjugated oligomers and polymers: synthesis, characterization, and applications. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

This PhD thesis was aimed at design and synthesis of new functional organic polymers and macromolecules using 1,4-dithiafulvenes (DTFs) and tetrathiafulvalene vinylogues (TTFVs) as molecular building blocks. Despite enormous synthetic difficulties encountered at the initial stage of this work, reliable synthetic methodologies based on Suzuki coupling, phosphite-promoted olefination, and oxidative dithiafulvenyl dimerization reactions were successfully established, which led to the accomplishment of three research projects. The first project investigated a series of bis(DTF)-end-capped fluorene derivatives which were prepared and subjected to a one-pot iodine-promoted oxidative polymerization to yield π-conjugated co-oligomers containing tetrathiafulvalene vinylogue and fluorene repeat units. The resulting π-oligomers were characterized to take either acyclic or cyclic molecular structures, depending on the π-conjugation length of the monomer used for the polymerization. Electronic and electrochemical redox properties were examined by UV−vis spectroscopic and cyclic voltammetric analyses, while the supramolecular interactions of the π-oligomers with single-walled carbon nanotubes were investigated by UV−vis−NIR and Raman spectroscopy. In the second project, DTF end groups were linked to the 1 and 8 positions of a pyrene core directly or via phenylene bridges to afford redox-active pyrene derivatives. Upon oxidation, the 1,8-bis(DTF)pyrene underwent stepwise electron transfers to form radical cation and dication species, whereas the phenylene-extended bis(DTF)pyrene derivative was cyclized into a macrocyclic trimer through sequential DTF oxidative coupling reactions in solution and in the solid state. The structural, electronic, and supramolecular properties of the pyrene-based macrocycle were investigated using various spectroscopic techniques and molecular modeling studies. In the third and last project, redox-active DTF groups were attached to dendritic oligo(phenylene vinylene)s, which contain a non-planar, twisted anthraquinodimethane core. The ability of these π-electron rich molecules to bind with nitrobenzene and its derivatives was demonstrated, and their electrochemically generated polymer thin films were tested as efficient sensors for nitrobenzene.

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