Gas-Phase Studies of Organic Biradicals

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With this Renewal award, the Organic and Macromolecular Chemistry Program in the Chemistry Division supports the work of Dr. Hilkka I. Kenttamaa of the Department of Chemistry at Purdue University. This research provides long-sought-after reactivity information for elusive aromatic biradicals. Reactivity studies on organic biradicals are hindered by their high reactivity and short lifetime in solution. Very little is currently known, for example, about reaction kinetics and selectivity of many aromatic biradicals, and even less about the factors that control this reactivity. However, it is highly desirable to obtain such information since aromatic biradicals play a key role in many reactions, ranging from organic synthesis to the biological effects of antitumor antibiotics. In the past, the PI and her research group have developed gas- phase methodology for the characterization of organic radicals. This methodology is now adapted for the examination of biradicals. Kinetic reactivity studies are carried out on isolated biradicals in the gas phase by using FT-ICR mass spectrometry. The radicals are manipulated in the mass spectrometer via a chemically inert charged group attached to the radical (distonic ion approach). Identification of reaction products and determination of reaction rate constants for many different reaction systems yields new information on the fundamental factors that control organic biradicals reactivity. The specific effects of the charged group are independently explored. Thermochemical information is obtained using a flowing-afterglow quadrupole-octopole-quadrupole apparatus. This instrument is also used to study in detail some of the novel triply- charged addition products formed in the biradical reactions. Molecular orbital calculations are carried out to theoretically examine the systems in collaboration with two experts, Dr. John Nash (Purdue) and Professor Chris Cramer (U.Minnesota).The Organic and Macromolecular Chemistry Program in the Chemistry Division supports Dr. Hilkka I. Kenttamaa of the Department of Chemistry at Purdue University who will develop new experimental methodologies for characterization of elusive reaction intermediates that will have an impact on experimental physical organic chemistry. Fundamental knowledge obtained on the properties of poorly understood organic biradicals will facilitate the rational design of biradicals with properties tailored for use, for example, in organic synthesis and in new cancer treatments. Professor Kenttamaa will continue her excellent track record in promoting the integration of research and education. Previous accomplishments have seen more than 20 graduate and undergraduate students carry out all the aspects of the research and disseminate the results under Professor Kenttamaa's supervision. Ten PhD's graduated and each secured an excellent job in industry, national laboratories or academia during the last grant period. About half of the participating students are female or belong to underrepresented groups (mostly African-American). Geographic diversity includes, students from South Africa, Ghana, Nigeria, India, China, Belize, Canada and the US. Professor Kenttamaa's results will continue to be published in peer reviewed chemistry journals and disseminated via seminars given by Professor Kenttamaa and her students at national and international conferences on organic, biological and analytical chemistry, mass spectrometry and gas-phase ion chemistry, and in undergraduate and graduate colleges. Industrial collaborations and visits currently with Lilly, Lubrizol, Exxon, will continue.