Gas-phase studies on the reactivity of charged, aromatic σ,σ,σ-triradicals by using distonic ion approach and Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry

Bartlomiej J Jankiewicz, Purdue University

Abstract

Reactive intermediates with unpaired electrons, such as organic monoradicals and polyradicals, play an important role in organic synthesis, development of new organic materials, and the biological activity of organic compounds. While the chemical properties of various mono- and biradicals have been examined theoretically and experimentally, no reactivity studies have appeared previously on related triradicals. The research on these species was limited to the generation of three such species, and theoretical investigations of their and other triradicals' electronic states and structures. This thesis describes the first reactivity study on a σ,σ,σ–triradicals. The Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR) and “distonic ion approach” were employed to characterize the reactivity of σ,σ,σ–triradicals. The understanding of the reactivity of triradicals cannot be achieved without knowledge of related mono- and biradicals. Therefore, the discussion about the reactivities of the σ,σ,σ–triradicals is preceded by description of chemical behavior of related σ–mono- and σ,σ–biradicals. The examination of the reactivities of a new pyridine-based monoradicals toward selected neutral reagents extends knowledge about chemical behavior of these species. Similarly to previously reported studies, the observed reaction efficiency ordering in most cases correlates well with ordering of the monoradicals electron affinities. The characterization of the chemical properties of the six unsubstituted didehydropyridinium ions and examination of the effect of the substitution on the reactivity of meta-isomers provides valuable data to biradicals reactivity controlling factors studies. The reactivity of the all biradicals is controlled by electron affinity and singlet-triplet gap. The reactivity of the meta-biradicals is additionally controlled by dehydrocarbon atom separation. The first reactivity studies on a σ,σ,σ–triradicals, tridehydropyridinium ions, not only provide information about the chemical properties of the triradicals but also advance our understanding of the spin/spin interactions within the polyradicals. Additionally, the effect of the substitution on the reactivity of one of the isomeric tridehydropyridinium ions is described.

Degree

Ph.D.

Advisors

Kenttamaa, Purdue University.

Subject Area

Organic chemistry|Physical chemistry

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