Mechanism of Ferric Oxalate Photolysis

Abstract

Iron(III) oxalate, Fe 3+ (C 2 O 4) 3 3-, is a photoactive metal organic complex found in natural systems and used to quantify photon flux as a result of its high absorbance and reaction quantum yield. It also serves as a model complex to understand metal carboxylate complex photolysis because the mechanism of photolysis and eventual production of CO 2 is not well understood for any system. We employed pump/probe midinfrared transient absorption spectroscopy to study the photolysis reaction of the iron(III) oxalate ion in D 2 O and H 2 O up to 3 ns following photoexcitation. We find that intramolecular electron transfer from oxalate to iron occurs on a subpicosecond time scale, creating iron(II) complexed by one oxidized and two spectator oxalate ligands. Within 40 ps following electron transfer, the oxidized oxalate molecule dissociates to form free solvated CO 2(aq) and a species inferred to be CO 2 •-based on the appearance of a new vibrational absorption band and ab initio simulation. This work provides direct spectroscopic evidence for the first mechanistic steps in the photolysis reaction and presents a technique to analyze other environmentally relevant metal carboxylate photolysis reactions.

Slow thermal equilibration in methylammonium lead iodide revealed by transient mid-infrared spectroscopy

“…30 for a representative probe spectrum). Details of the experimental setup have been described elsewhere 57 . Samples were mounted in a liquid-nitrogen-cooled, cold-finger cryostat with a base pressure below 1 × 10 −6 Torr in all the optical measurements.…”

Surface chemistry of quantum-sized metal nanoparticles under light illumination

“…79,80 Transient infrared (IR) absorption spectroscopy provides an additional technique to probe the dynamics of transient states of adsorbate species that are responsible for IR absorption. 81 Although fully understanding the transient dynamics of hot electrons involved in hot-electrondriven photocatalytic reactions is signicantly challenging, researchers are continuously advancing the characterization techniques to enable the study on the relaxation processes of the high-energy hot electrons with high resolution in both spatial and temporal space. The foreseeable research activities will eventually bring useful information together to help understand the sequential quantum processes related to the relaxation and ow of hot electrons.…”

Application Limits of the Ferrioxalate Actinometer

“…[40] In subsequent studies, this theory was supported by molecular dynamics simulations and according spectroscopic findings. [46,47] Another effect that contributes to a lower quantum yield at intense radiation is a higher rate of the recombination of CO 2…”