[Fe-Fe]-Hydrogenase Model Photochemistry

Fe-Fe Hydrogenases are organometallic enzymes capable of catalyzing the reversible oxidation of the molecular hydrogen. The enzyme’s active site is a di-iron complex with an azadithiolate bridge and CO and CN- ligands. The design of the active site has inspired the synthesis of numerous structural and functional models of the Fe-Fe hydrogenase, in an effort to better understand its catalytic activity and other physical/chemical properties. Interestingly, previous studies have shown that the hydrogenase enzyme’s activity is inhibited in the presence of CO and that this inhibition is reversible in the presence of light. Later studies have demonstrated that hydrogenase model complexes, such as (μ-1,3-propanedithiolate)-hexacarbonyldiiron ((μ-pdt)[Fe(CO)3]2), are photochemically active. Our interest is in synthesizing structural and functional models of the [FeFe] hydrogenase active site in order to study their thermal and photochemical reactivity. The focus of this poster is to showcase our synthetic strategies of  structural models with different bridgehead ligands in order to study the effect of electronic factors on the photochemical properties of the complexes, and thermal reactivity of the photoproducts. Photochemistry experiments are carried out in different solvents which act as reactants with the photoproduct.   Experiments are performed to quantify the efficiency of the photochemical reaction and qualitatively to understand spectral profiles of reactants and products. This poster will showcase our understanding of both qualitative and quantitative photochemistry of structural models of Fe-Fe hydrogenase and implications for making catalysts for hydrogen activation.