Gas-Phase Studies of Substituted Aromatic Radicals, Biradicals and Polyradicals

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With the support of the Organic Dynamics Program and the Office of Multidisciplinary Activities of the Mathematical and Physical Sciences Directorate, Professor Hilkka I. Kenttamaa, of the Department of Chemistry at Purdue University, carries out gas-phase studies of substituted aromatic radicals, biradicals, and polyradicals. By generating aromatic radicals which incorporate a positively charged group, Professor Kenttamaa is able to employ Fourier-transform ion cyclotron resonance mass spectrometry to examine their intrinsic or solvent-free reactivity under clean conditions, permitting the assessment of reaction rate constants, product branching ratios, and thermochemical parameters such as bond dissociation energies. Substituent effects are explored for phenyl, benzyl, and other aromatic mono- and polyradicals carrying neutral substituents in addition to the remote charged groups, and radical traps are employed to probe the importance of polar effects in different types of radical reactions. For biradicals, the relationship between reactivity and predicted ground state multiplicity is examined, and this information is used to search for spin-selective gas-phase reactions. Professor Hilkka I. Kenttamaa, of the Department of Chemistry at Purdue University, with the support of the Organic Dynamics Program and the Office of Multidisciplinary Activities of the Mathematical and Physical Sciences Directorate, studies the chemistry of molecules containing one or more unpaired electrons (`radicals`). By appropriate choice of radicals, Professor Kenttamaa is able to employ gas-phase techniques to study their formation and reactivity, permitting an assessment of their intrinsic properties in the absence of the complicating influences of solvents or other potentially reactive species. Through these studies is gained fundamental knowledge regarding the chemistry of electron-deficient molecules, advancing the understanding of the roles of substituent effects and polar effects in governing their reactivity and offering potential advances in the areas of radical-based organic synthesis and organic materials research.