Synthetic studies on new teropyrenophanes and pyrenophanes

Ghasemabadi, Parisa Ghods (2019) Synthetic studies on new teropyrenophanes and pyrenophanes. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Cyclophane chemistry came into existence in the middle of 20th century with Brown and Farthing’s synthesis of [2.2]paracyclophane. During the six subsequent decades, interest in cyclophanes has grown significantly due to their interesting structural, spectroscopic, conformational, physical and chemical properties, especially with regards to highly-strained cyclophanes. 1,1,n,n-tetramethyl[n](2,11)teropyrenophanes are a remarkable class of cyclophanes, which have been successfully synthesized using two related strategies. The first chapter of this dissertation involves the seminal work on the cyclophane chemistry of ropyrene series including benzene, pyrene and teropyrene. Different general strategies and the chemical, spectral and photophysical properties of each series of cyclophanes have been discussed. The second chapter focuses on the application of these synthetic strategies and also the development of other approaches for the synthesis of 1,1,6,6-tetramethyl[6](2,11)teropyrenophane, which would become the smallest and most strained member of teropyrenophane series. Although all attempts to arrive at this highly challenging target were unsuccessful, several notable advances were made, and these may open new avenues of investigation. The third chapter studies a modified protocol for the key teropyrene-forming reaction (a valence isomerization/dehydrogenation (VID) reaction), which has enabled the construction of the teropyrenophanes on a gram-scale. This provided the opportunity to explore new aspects of their chemistry, i.e. through K-region oxidation and reaction with o-phenylenediamine, which resulted in the synthesis of larger bent PAHs; quinoxalinoteropyrenophanes. In the last chapter, some of the aliphatic bridge carbon atoms in teropyrenophane system were replaced with a small aromatic system (pyridine). Titration of this novel cyclophane (pyridinophane) with TFA was performed and a weak charge transfer band was observed in UV-Vis acid titration spectra due to the intramolecular transition between the teropyrene and pyridinium units, which did not exist in neutral pyridinophane. In addition, remarkable progress was made towards the synthesis of pyridine-containing pyrenophane, but more investigation is required in this area. These new types of compounds offer opportunities to investigate their host-guest chemistry and have the potential for application in the design of optoelectronic devices.

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