CAS: Ultrafast Spectroscopy and Photoisomerization of Iron Sulfoxide Complexes

With support from the Chemical Structure, Dynamics & Mechanisms-B (CSDM-B) Program of the Chemistry Division (CHE), and the Established Program to Stimulate Competitive Research (EPSCoR), Professor Jeffrey Rack of the University of New Mexico is developing new classes of iron complexes with interesting spectroscopic and magneto-optical properties. The goal of this research is to design new photoactive iron complexes with sulfoxide ligands. The project lies at the interface of organic, inorganic, and physical chemistry, and is appropriate for education of scientists at all levels of experience. The University of New Mexico is a majority minority institution and the Rack research group is works to provide the highest level of education and training for students underrepresented in science and will continue to do so under this award. Outreach activities involving the training of high school and middle chemistry teachers is part of the research project. The proposed work details a research plan to create photoactive iron polypyridine sulfoxide complexes. The goal of this work is to discover if phototriggered sulfoxide isomerization can be supported on iron centers in a fashion similar to that on related ruthenium complexes. In ruthenium complexes, 3MLCT excitation prompts transient Ru3+ formation, which induces excited state isomerization of the sulfoxide from S-bonded to O-bonded. Professor Rack and his research team aim to reproduce this photochemistry on iron with the objective of stabilizing high or intermediate spin states with the O-bonded coordination mode. There are two major challenges that must be met to observe this chemistry on iron: 3MCLT (metal-to-ligand charge-transfer) states on iron are rare due to the primogenic effect and sulfoxide isomerization on iron has not been reported. Preliminary results provide evidence that these challenges can be overcome and that the goal of achieving S- to O-sulfoxide bonding on iron can be achieved. If successful, the ability to achieve such intermediate to high spin state Fe-sulfoxide complexes would be a significant advance for the field as this would bring this chemistry into the realm of earth abundant transition metal space, and open up an important new avenue of exploration for organometallic chemists. 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.