New organic π-conjugated system using dithiafulvenes and tetrathiafulvalenes and building blocks

Younes, Eyad Ahmad (2017) New organic π-conjugated system using dithiafulvenes and tetrathiafulvalenes and building blocks. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

This thesis describes a systematic study of new functional π-conjugated organic materials. The detailed investigations can be summarized in two research themes. The first theme deals with the design and synthesis of redox-active conjugated co-polymers using tetrathiafulvalene vinylogue (TTFV) and pyrene as repeat units. TTFV has been known to be an excellent π-electron donor and shows intriguing conformational switching properties associated with its redox reactions. Pyrene is a widely used organic chromophore with rich photophysical and supramolecular properties. The newly designed TTFV-pyrene co-polymers have been found to show redox-activity and stimuli-responsive aggregation behaviour in organic solvents. Their electronic and supramolecular properties have been elucidated by various spectroscopic and microscopic analyses (e.g., CV, UV-Vis, GPC, and DLS). In addition, the conformational properties of the co-polymers were modeled by molecular mechanics (MM) simulations to provide theoretical explanations for the obtained experimental data. In the second research theme, efforts have been dedicated to the development of new π-extended analogues based on pentacene-5,7,12,14-tetraone. By introducing redox-active 1,3-dithiole groups via Wittig-type olefination, a highly π-extended TTF analogue was created, and its structural, electronic, and redox properties were investigated by NMR, UV-Vis absorption and electrochemical analyses in conjunction with density functional theory (DFT) calculations. Pentacene-5,7,12,14-tetraone was also subjected to selective olefination and cross-coupling reactions to yield a new class of pentacene-based π-conjugated systems functionalized with geminal enediyne and 1,3-dithiole groups. The electron-donating and accepting effects exerted by the enediyne and dithiole units deliver intriguing structural and electronic properties, as well as redox activities which were systematically investigated by experimental and theoretical analyses. The bis(enediyne) substituents also provided synthetic access to novel carbon-rich cross-linked polymers and polycyclic aromatic hydrocarbons (PAHs) through transition metal-catalyzed cross-coupling and cyclization reactions.

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