Understanding the Photochemistry Of Iron Complexes Using Time-Resolved X-ray Spectroscopy

Iron is an earth abundant transition metal found in numerous natural and synthetic chemical processes making it an archetype for exploring and understanding new areas of chemistry and physics. Iron has been shown to be a viable substitute as a far less expensive and toxic alternative to ruthenium and osmium metal complexes, but with the risk of altering the chemical reaction dynamics. Therefore, it is paramount to understand and characterize the reaction dynamics and possible intermediate species in order to control the iron based chemical reactions. In this work we explore the interesting photochemistry of a bistable spin-crossover iron complex, which can be reversibly switched by light irradiation. The attractive use of light to change the spin-state of the system for potential applications in molecular electronics and spintronics. The system uses a photochromic ligand that isomerizes upon light absorption, and in turn induces a modification in the ligand field resulting in a change of the spin-state that is stable at room temperatures. Due to their novelty, these systems have been scarcely studied, and the mechanism behind the ligand field modification is still unclear. Therefore, to elucidate the ligand-driven light-induced spin change mechanism we utilize hard x-ray absorption and x-ray emission spectroscopy techniques at the liquid-jet endstation of the Advanced Photon Source (APS), where we can take advantage of the high-repetition-rate, ultra-stable, and widely tunable x-ray pulses.