Salami, Fatemeh (2025) Exploration of π-fused polycyclic aromatic systems as Redox-active materials and fluorescence sensing probes. Doctoral (PhD) thesis, Memorial University of Newfoundland.
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Abstract
This thesis presents a comprehensive investigation into the synthesis and application of novel chromophores and fluorophores exhibiting internal charge transfer (ICT) properties. The research employs efficient synthetic methodologies, including Suzuki coupling, olefination reactions, and one-pot condensation reactions, to construct well-designed small molecules with distinct donor and acceptor moieties. Subsequently, the study explores the practical applications of these newly synthesized ICT compounds in environmental sensing and pollutant capture, focusing on the detection and sequestration of persistent organic pollutants such as perand polyfluoroalkyl substances (PFAS) and cyclo-di-bisphenol A diglycidyl ether (cyclo-di-BADGE) employing both experimental and computational studies. The thesis, organized into four chapters, comprehensively explores the design, synthesis, characterization, and application of novel organic compounds for environmental remediation and sensing technologies. The first project focuses on the synthesis and characterization of novel donoracceptor (D/A) conjugated systems featuring dithiafulvenyl (DTF) end groups linked to fluorenones or fluorenylidene-1,3-dithioles through phenylene bridges. The compounds, with linear or wedge-shaped structures, were analyzed using X-ray diffraction, UV-vis spectroscopy, and DFT calculations. Cyclic voltammetry revealed that DTF groups undergo oxidative coupling to form polymers with varied redox activities. The study demonstrates how structural variations influence the electronic and electrochemical properties of these D/A systems. The second project investigates a new class of organic π-chromophores which contain an electron-donating 1,4-dithiafulvenyl group in conjugation with an electronwithdrawing 8H-benzo[e][1,2,4]triazolo[3,4-b][1,3,4]thiadiazin-8-one (BTTD) core in their molecular structures. The synthesis of these compounds used a phosphitepromoted olefination reaction as a key step, through which 1,3-dithiole-2-thione was reacted with corresponding benzotriazolothiadiazinone counterparts to form a flat polycyclic π-framework, allowing electron push-pull effects to occur. The resulting donor-acceptor chromophores were found to exhibit significant ICT properties, giving strong absorption in the visible region of the spectrum. The triazolyl unit in these molecules can be protonated by strong acids to show enhanced ICT effects, while electrochemical analysis revealed that these compounds possess amphoteric behavior with tunable band gaps and are potentially useful organic semiconductors. We also demonstrated that this type of chromophore can be readily functionalized on the surface TiO₂ nanoparticles without losing absorption performance. Finally, the dithiafulvenyl group incorporated in the molecular structure was found to enhance antibacterial activity, rendering the chromophores potential application in antibacterial/antimicrobial coatings. The third project presents a new class of benzothiadiazole (BTD)-centered donor–acceptor–donor (D–A–D) organic fluorophores, where the central BTD core is symmetrically flanked by π-fused phenanthroimidazolyl or pyrenoimidazolyl donor groups. This design promotes bidirectional electron delocalization, enhancing ICT properties and enabling dual fluorescence emission. The synthesized fluorophores exhibit pronounced solvatofluorochromic effects, with emission properties highly sensitive to microenvironmental changes. We further demonstrated their application as effective probes for per- and polyfluoroalkyl substances (PFAS), showcasing distinct fluorescence responses based on PFAS chain lengths. Notably, phenanthroimidazolederived fluorophores exhibit significant blueshifts upon interaction with shorter-chain PFAS, while longer-chain PFAS induce quenching effects. These findings highlight the potential of our BTD-centered D-A-D fluorophores for developing advanced sensor arrays capable of rapidly discriminating PFAS in complex mixtures and further expand the toolbox for molecule-based luminescent sensing and molecular recognition. The fourth and last project presents the first comprehensive characterization of cyclo-di-BADGE, a macrocyclic compound previously known only as a by-product in bisphenol A (BPA) and bisphenol A diglycidyl ether (BADGE) co-polymerization. Using NMR, X-ray diffraction, and computational methods, this research project explored its molecular structure and conformations. The study also investigated cyclo-di-BADGE’s aggregation behavior in various media through experimental and simulation techniques. Additionally, its interaction with bovine serum albumin (BSA) was examined, providing insights into the compound’s potential environmental and biological impacts.
| Item Type: | Thesis (Doctoral (PhD)) |
|---|---|
| URI: | http://research.library.mun.ca/id/eprint/16998 |
| Item ID: | 16998 |
| Additional Information: | Includes bibliographical references (pages 190-233) -- Restricted until May 5, 2026 |
| Keywords: | PFAS, polycyclic aromatic, fluorescence sensing probes, DTF, redox-active materials |
| Department(s): | Science, Faculty of > Chemistry |
| Date: | May 2025 |
| Date Type: | Submission |
| Library of Congress Subject Heading: | Polycyclic aromatic compounds; Fluorescence, Sensitized; Oxidation-reduction reaction |
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