This award in the Chemical Synthesis (SYN) program supports work by Professor Jeffrey M. Zaleski at Indiana University to probe the geometric and electronic factors that control metal-catalyzed and photochemical diradical generation by Bergman cyclization. The unusual diyne-ene chemical functionality undergoes cyclization to form a highly reactive diradical intermediate that can trigger and participate in polymerization reactions, as well as undergo radical reactions with chemical substrates. The reactions can be controlled by choice of metal catalyst and structure of the bound enediyne motif, or by the nature of the chromophore used to trigger the reaction with light. Four chemical systems that span different architectural classes of molecules from large porphyrin chromophores to small inorganic molecules and coated nanoparticles will be prepared and their reactivities examined. The structures of complexes and their electronic properties will be correlated with the activation energy required to generate potent diradicals. Parameters from the most facile systems will then be used to screen their reactivities against chemical substrates.
The results may ultimately contribute to applications of radicals in synthetic chemistry as well as advanced chemical reagents for magneto- or phototherapy in hypoxic environments. The project is also multifaceted in synthesis and spectroscopy, and thus develops undergraduate and graduate students on both preparative and mechanistic chemical foundations.
Our research interests lie in developing a better fundamental understanding of the factors that control reactions metal-triggered chemical radicals. Radical chemistry of this type is relevant to biological processes, new therapeutics, and fundamental reactions in the environment. The intellectual merit of our work involves the development and analysis of metal-controlled radical reactions triggered by light or heat in order to predict and control the pathway to new chemical species. The broader impacts of the proposed work are centered in the potential use of these radicals for new therapeutics for cancer and plaques (arterial and neuronal), novel nano-scale materials for ultra-light electronics, as well as new plastic materials in tunable structures. Additionally, our work trains undergraduate, graduate, and postdoctoral students for future careers in chemical, biological, and physical sciences. Such a multifaceted project in preparation and measurement educates students on all aspects of chemical sciences and insures a supply of trained scientists and engineers for the future. Graduates from the PI's group work in water purification, pharmaceuticals, naval weapons, scientific writing for the public, as well as multidisciplinary companies like 3M in all aspects involving new materials and polymers. Numerous undergraduates have also gone on to graduate programs at top science departments around the country (Wisconsin, Minnesota, Illinois, Caltech etc.).
