Functional organic fluorophores based on 1,3-dithiafulvene and pyrene

Shahrokhi, Farshid (2020) Functional organic fluorophores based on 1,3-dithiafulvene and pyrene. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

This thesis demonstrates the design, synthesis, and application of fluorene and pyrene-based organic π-systems, in which redox-active 1,3-dithiafulvenyl (DTF) groups are incorporated. The detailed studies encompass three classes of novel redox-active organic fluorophores. The first project deals with fluorene-cored π- conjugated phenylene vinylene dendrimers with DTF end groups attached to the peripheral positions. The oxidative coupling reactivity of the DTF group allowed these dendrimers to undergo facile electropolymerization on conductive substrates. By means of multi-cycle cyclic voltammetric scans, redox-active microporous polymer thin films were successfully generated. The redox-active polymer prepared through a double-layer strategy, in which a polymer thin film prepared from a dithiafulvenylsubstituted phenylacetylene precursor was surface-modified with a fluorene-cored phenylene vinylene dendrimer carrying dithiafulvenyl end groups. The experimental results indicated that the polymers can act as highly sensitive and selective electrochemical sensors for 2,4,6-trinitrotoluene (TNT), one of the most important nitroaromatic explosives. In the second project, a group of DTF-functionalized pyrene derivatives was prepared and investigated. The redox activities and electrochemical properties of these compounds were examined by voltammetric analysis. Polymer films generated through electropolymerization of these redox-active pyrenes have been found to show responsiveness to nitromethane. In addition, one of the derivatives shows an unusually high efficiency in terms of hydrogen/deuterium exchange, which can be potentially used for trapping deuterium isotope. The third project focuses on a comparative study of a series of new Kregion functionalized pyrene derivatives. Three new K-region functionalized pyrene derivatives were synthesized using pyrene-4,5-dione as the starting material. The Xray single crystal structures of three compounds were determined and examined by the Hirshfeld surface analysis. The molecular geometries of these pyrene derivatives were found to strongly affect the intramolecular noncovalent interactions in the solid state. Moreover, the electronic and electrochemical redox properties of these pyrene derivatives were characterized. Among the three pyrene derivatives, a dithiafulvenyl substituted derivative presents an intriguing D{A conjugated system with a small bandgap (Eg) and amphoteric redox behavior, making this compound a potentially useful organic semiconductor. The findings disclosed in this work show promise for the development of pyrene-based organic solid materials for advanced optoelectronic applications. The fourth and last project investigates a new class of pyreno/phenanthroannulated 1,3-diaza-4-azulenones, which could be readily synthesized through a straightforward one-pot condensation approach. The molecular properties of these compounds were analyzed by single-crystal X-ray crystallography, UV-vis absorption, and fluorescence spectroscopy. Our results showed that the emission behavior of these compounds is highly sensitive to solvent polarity and acidity, rendering them novel fluorosolvatochromic and acidochromic dyes that can be potentially utilized in chemosensing and bioimaging applications.

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