Studies of the halogen bond and electron transfer in prototypical donor-acceptor halogen-bonded complexes

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In this project supported by the Chemical Structure, Dynamics and Mechanisms Program of the Division of Chemistry, Professor Scott Reid of Marquette University will study non-covalent interactions involving halogen atoms, which are fundamentally important in diverse areas in chemistry and biochemistry from protein-ligand interactions and drug discovery to molecular recognition and self-assembly to electron transfer and organic synthesis. The strength of halogen bonds can rival or exceed that of hydrogen bonds, and just as our ever-evolving understanding of the hydrogen bond has been aided to a great degree by the study of model systems, the study of halogen bonding requires fundamental probes of interactions in prototypical systems, which is the focus of this proposal. In particular, the need exists to systematically correlate properties of the donor/acceptor with structural characteristics of halogen bonding. Prof. Reid and co-workers will probe the structure, properties, reactivity and electron transfer dynamics of prototypical halogen bonded systems, using matrix isolation methodologies in combination with spectroscopic probes from the far-IR to UV region, with assistance from high level ab initio theory. A key aspect of this work is the combination of experimental and computational methods that will be brought to bear on this important problem. The charge transfer character of donor-acceptor complexes and the dynamics of electron transfer in these systems are key issues that underpin much of organic reactivity, and the photochemical studies described herein will provide valuable information on the dynamics associated with photoinduced electron transfer across halogen bonds. Through the study of model complexes in the key classes of halogen bonded interactions (à-systems, O and S atom donors, N and P atom donors), fundamental new insights will be provided into the nature of halogen bonding, which will aid the development and refinement of theoretical methods. The project results will be disseminated by publication in high quality journals and participation at national and international scientific meetings such as the International Symposium on Molecular Spectroscopy, for which the PI currently serves as Chair of the International Advisory committee. The PI will also use this project to broaden the participation of underrepresented groups in research.