Borylated Bisphenol and Bisphenoxyl Mono-radicals: Synthesis, Magnetic Properties and Stability Studies
Date Issued
2016
Date
2016
Author(s)
Chung, Ming-Han
Abstract
Phenols and phenolates have been known as natural antioxidants and their oxidation products are generally the phenoxyl radicals; however, the studies of the decomposition pathway of phenoxyl radicals are relatively rare. In this work, a series of bisphenoxyboryl monoradicals have been prepared and their ESR measurements confirm the delocalization of the unpaired electron to the boron center with hyperfine-coupling constants of 4.8 G and 1.6 G to the 11B (I = 3/2) and 10B (I = 3) nuclei, respectively. Interestingly, compared to the persistent dimesitylboryl phenoxyl radical, the bisphenoxyboryl mono-radicals are unstable at room temperature and decompose to yield the carbon-carbon coupling product.The decomposition process of the reported mono-radicals is postulated to proceed through an ESR-silent radical dimer, which features a longer lifetime in non-coordinating solvent. On the other hand, two-electron oxidation of the borylated bisphenoxides results in a complex mixture, which is proposed to arise from the formation of the unstable singlet borylated bisphenoxydiradicals.
Subjects
phenol
phenolate
phenoxyl radical
SDGs
Type
thesis
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