Photochemistry of Fe:H2O Adducts in Argon Matrixes: A Combined Experimental and Theoretical Study in the Mid-IR and UV-Visible Regions.

Abstract

The photochemistry of Fe:H2O adducts is of interest in fields as diverse as catalysis and astrochemistry. Industrially, iron can be used as a catalyst to convert H2O to H2, whereas in the interstellar medium it may be an important component of dust grains, influencing the chemistry on their icy surfaces. This study consisted of the deposition and spectral characterization of binary systems of atomic iron with H2O in cryogenic argon matrixes. In this way, we were able to obtain information about the interaction of the two species; we observed the formation of adducts of iron monomers and dimers with water molecules in the mid-IR and UV-visible spectral domains. Upon irradiation with a UV radiation source, the iron species were inserted into the water molecules to form HFeOH and HFe2OH, leading in some cases to the formation of FeO possibly accompanied by the production of H2. DFT and correlated multireference wave function calculations confirmed our attributions. This combination of IR and UV-visible spectroscopy with theoretical calculations allowed us to determine, for the first time, the spectral characteristics of iron adducts and their photoproducts in the UV-visible and in the OH stretching region of the mid-IR domain.