Hydrogen is one of the fuels of the future due to its characteristics, photocatalytic production of hydrogen from the water-splitting under sunlight as the main source of energy is a promising technology1. Hydrogenases are natural enzymes that catalyse the production of H2 in the photosynthesis process 2 Among all the hydrogenases Fe-Fe complexes present higher catalytic activity with turn over frequencies (TOF) up to 6000-9000 s-1 for H2 production in water in comparison to other hydrogenases, making them a competitive substitute of platinum as a catalyst for hydrogen production3–5. This work presents the intrinsic photophysics and photoreactivity of the complexes Fe2(bdt)(CO)6 and Fe2(dpet)(CO)6 (Figure 1) for its application in the photocatalytic H2 production under solar light, determined by Transient Absorption (TA), Time-resolved infrared spectroscopy (TRIR) (Figure 2), Cyclic voltammetry, IR Spectroelectrochemistry (FTIR-SEC) and their photostability. The calculated values for the redox potentials are Ered -1.26 V and Eox -1.18 V for Fe2(bdt)(CO)6, and Ered -1.39 V and Eox - 1.26 V for Fe2(dpet)(CO)6 vs Fc-/Fc+ both reversible associate to a one-electron Fe1Fe1 to Fe1Fe0 redox process. From the FTIR-SEC we concluded that Fe2(dpet)(CO)6 is reversible to the reduction processes and photostable under visible light, we adjusted to two lifetimes 12 ps from the internal conversion processes and vibrational cooling and 250 ps from the Fe-CO vibrational relaxation.

Photophysics of the Fe=Fe hydrogenase mimics complexes

ACS Fall 2021

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