Ultrafast photoelectron spectroscopy of photoexcited aqueous ferrioxalate

The photochemistry of metal-organic compounds in solution is determined by both intra- and inter-molecular relaxation processes after photoexcitation. Understanding its prime mechanisms is crucial to optimise the reactive paths and control their outcome. Here we investigate the photoinduced dynamics of aqueous ferrioxalate ([Fe-III(C2O4)(3)](3-)) upon 263 nm excitation using ultrafast liquid phase photoelectron spectroscopy (PES). The initial step is found to be a ligand-to-metal electron transfer, occuring on a time scale faster than our time resolution (less than or similar to 30 fs). Furthermore, we observe that about 25% of the initially formed ferrous species population are lost in similar to 2 ps. Cast in the contest of previous ultrafast infrared and X-ray spectroscopic studies, we suggest that upon prompt photoreduction of the metal centre, the excited molecules dissociate in <140 fs into the pair of CO2 and [(CO2)Fe-II(C2O4)(2)](3-) fragments, with unity quantum yield. About 25% of these pairs geminately recombine in similar to 2 ps, due to interaction with the solvent molecules, reforming the ground state of the parent ferric molecule.

Automated summary

The study reveals that upon 263 nm excitation, aqueous ferrioxalate undergoes a ligand-to-metal electron transfer, followed by dissociation of excited molecules into CO2 and [(CO2)Fe-II(C2O4)(2)](3-) fragments, with approximately 25% recombining to reform the ground state of the parent ferric molecule.