With this award, the Organic and Macromolecular Chemistry Program supports Professor Gudmundsdottir of the University of Cincinnati whose research will focus on selectively forming, detecting and investigating the reactivities of vinyl nitrene intermediates in solution and in the solid state. Direct irradiation of vinyl azides yields azirine products that can be attributed to formation of singlet vinyl nitrenes or can come from concerted rearrangement of the singlet excited state of the vinyl azides. Similarly, direct photolysis of 2H-azirine derivatives forms singlet biradicals. In order to bypass the singlet reactivity of the vinyl azide and 2H azirine precursors, vinyl azide and 2H-azirine derivatives with build-in triplet sensitizers have been prepared. The triplet vinyl nitrene intermediates that are expected to form by photolysis of these vinyl azides and 2H-azirines will be characterized using laser flash photolysis and matrix isolation. A detailed picture of the reactivities and kinetics of triplet vinyl nitrenes in solution will be obtained. Preliminary results imply that laser flash photolysis of 2H-azirine derivatives that have a built-in triplet sensitizer permit direct detection of triplet vinyl nitrene intermediates. These results have opened up a new field in nitrene chemistry and intermediates that have not previously been characterized can now be investigated. The solid state reactivity of these vinyl nitrene precursors will be studied in order to understand how their reactivity is affected by surrounding crystal lattices. The long term goal is to render these intermediates stable to explore their physical properties. The investigations that are proposed will lead to full characterization of triplet vinyl nitrenes in argon matrices and in solutions. Since the chemical reaction pathways for these intermediates in solution and in the solid state are largely unknown, they will be studied and identified. Molecular modeling will be performed to aid in the characterization of these compounds and to explain the reactivity of these intermediates. Better insight into the reactivity of triplet vinyl nitrenes will allow for the design of stable triplet nitrenes.

With this award, the Organic and Macromolecular Chemistry Program supports Professor Gudmundsdottir of the University of Cincinnati whose research will study triplet nitrene intermediates that have high spin properties and are therefore potential candidates for organic magnets. The quest for new organic materials with magnetic properties arises from their potential to provide new technological advantages for applications such as magnetic shielding, magneto-optical switching, and 'smart' materials. The proposed research will train graduate students to do fundamental research in physical organic chemistry. These graduate students will in turn train undergraduate students to do research and expose high school students to scientific research. Emphasis will be placed on attracting minority high school students to work on the proposed research.

Project Report

Fundamental research in chemistry has laid the foundations for the discovery and design of new materials with fascinating magnetic, electrical and optical properties, prompting inventions anywhere from "leak proof diapers", and faster computers to lighter long-range planes, which simplify and enhance our daily lives. Magnets have been used by humans for the last thousand years. The earliest magnets were used for compasses and were made from a lodestone, a mineral rich in iron ore. Currently, commercial magnets are still mainly based on transition-metal and their oxides. Recently, however, magnets have been reported that are based on unpaired electrons in organic molecules. The quest for new organic materials with magnetic properties arises from them being potentially both more cost effective and lighter than the more traditional metal and ceramic magnets, and thus be valuable in applications such as magnetic shielding and quantum computing. Furthermore, biocompatibility of organic magnets may potentially lead to interesting biological applications, such as magnetic imaging of medical implants. The pursuit of organic magnetic materials has sparked renewed interest in triplet nitrenes, which are ideal candidates because of their high spin properties. However, before we can intelligently construct high spin nitrene molecules, the subunits needs to be characterized, and thus we done fundamental studies on triplet alkyl- and vinylnitrene intermediates. We have characterized these intermediates using laser flash photolysis, time resolved IR spectroscopy, matrix isolation and ESR spectroscopy. We have also identified the reactivity of these intermediates in solution and in the solid state. We have shown that triplet alkylnitrenes are long lived intermediates that decay by dimerization whereas triplet vinylnitrene are shorter lived and their reactivity is limited by intersystem crossing. This research has also made it possible to train several graduate and undergraduate students to use state of the art instrumentation and learn critical thinking. Thus, these students have entered the workforce with more experience and better qualification.

National Science Foundation (NSF)
Division of Chemistry (CHE)
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Tyrone D. Mitchell
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University of Cincinnati
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