Synthesis and Properties of π- Extended Phenoxyl Radicals.

Abstract

Phenoxyl radicals are a class of π-radicals synthesized by single-electron oxidation of phenols. The spin density from the unpaired electron of a phenoxyl radical is highest at the oxyl position, as well as at the ortho and para positions relative to the oxyl group. The stability of phenoxyl radicals can be improved by substituents at the ortho and para positions, including aromatic, O, N, S-alkyl, and sterically hindered alkyl groups, which compensate for electronic deficiency through resonance or inductive effects. In 2016, Lemaire group reported a crystal structure of the stable phenoxyl radical 2,6-bis(8-quinolylamino)-4-(tert-butyl)phenoxyl (BAQP), which lacks the commonly utilized tert-butyl groups at the ortho position relative to the oxyl group. Moreover, the BAQP radical also showed reversible π-dimerization in solution. This thesis describes the synthesis and characterization of two sets of phenoxyl radicals that lack ortho tert-butyl groups, similar to BAQP. The first set of phenoxyl radicals is ortho-substituted with amino derivatives of large aromatic π-systems, namely pyrene, naphthalene, and phenalenone. The second set is the halogenated derivatives of the BAQP radical. This thesis also explores the stability and the reversible π-dimerization of both of the above-described novel sets of phenoxyl radicals. Notably, one of the radicals synthesized during this work, 5-(tert-butyl)l-2-oxy-1,3,-bis(1- prenylamino)benzene, was proven to be stable as crystal structures were obtained from the pure compound. This particular radical, like BAQP, showed reversible π-dimerization in solution detected by spectroscopic methods such as EPR and 1H-NMR spectroscopy methods. The solid- state properties of this radical were also explored through DC susceptibility measurements and EPR spectroscopy

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This paper was published in Brock University Digital Repository.

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