Iron(III) halide complexes as sustainable photocatalysts for radical-mediated reactions: mechanism, wavelength tunability and applications

In this project, Professor Dave Martin of the Department of Chemistry at The University of Iowa is investigating iron catalysts to perform new chemical reactions driven by light energy. Iron is a cheap, abundant and environmentally friendly metal, and iron catalysts have been shown to offer unique properties such as enabling different reactions depending on the color (wavelength) of visible light used to promote the reaction. New catalysts will be investigated and studies will be carried out to understand the origins of their unique behavior. This research will develop sustainable, practical and mechanistically understood methods to accomplish a variety of new reactions using inexpensive iron catalysts. In addition, the pursuit of this research will provide student training, research exposure to undergraduate students and opportunities for outreach and engagement with the community, promoting excitement and curiosity for the sciences. The development of inexpensive, earth-abundant and selective catalysts that can directly convert simple starting materials to value-added products is a major goal in organic synthesis. Iron catalysts are an attractive solution to address this challenge, and the goal of this research is to develop iron-based catalysts that enable a wide range of open shell transformations involving carbon-centered radicals. Prior work has shown that certain iron(III) halide catalysts are activated by visible light (up to 525 nm) and can selectively produce chlorine or bromine radicals in a catalyst- and wavelength-dependent manner, allowing several radical pathways to occur in a selective fashion. The Martin group will establish new methods for the conversion of C–H to C–C and C–X bonds including ring-forming reactions via acyl radicals and difunctionalizations of alkenes. Methodology development will be complemented by mechanistic studies to clarify ambiguity between competing mechanisms and new catalysts will be evaluated using experimental approaches combined with state-of-the-art computational methods. These studies will provide insight into the fundamental aspects of iron photochemistry and expand the range of visible light-promoted chemistry (including with wavelengths > 525 nm) with inexpensive, earth-abundant and environmentally benign metal catalysts. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.