From Local Covalent Bonding to Extended Electric Field Interactions in Proton Hydration. Issue 46 (25th October 2022)

• Record Type: Journal Article
• Authors: Ekimova, Maria; Kleine, Carlo; Ludwig, Jan; Ochmann, Miguel; Agrenius, Thomas E. G.; Kozari, Eve; Pines, Dina; Pines, Ehud; Huse, Nils; Wernet, Philippe; Odelius, Michael; Nibbering, Erik T. J.
• Is Part Of: Angewandte Chemie international edition. Volume 61:Issue 46(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-10-25
• Subjects: Eigen Cation -- Electronic Structure -- Hydrated Proton -- Soft X-Ray Absorption Spectroscopy -- Zundel Cation; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.202211066
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Seemingly simple yet surprisingly difficult to probe, excess protons in water constitute complex quantum objects with strong interactions with the extended and dynamically changing hydrogen‐bonding network of the liquid. Proton hydration plays pivotal roles in energy transport in hydrogen fuel cells and signal transduction in transmembrane proteins. While geometries and stoichiometry have been widely addressed in both experiment and theory, the electronic structure of these specific hydrated proton complexes has remained elusive. Here we show, layer by layer, how utilizing novel flatjet technology for accurate x‐ray spectroscopic measurements and combining infrared spectral analysis and calculations, we find orbital‐specific markers that distinguish two main electronic‐structure effects: Local orbital interactions determine covalent bonding between the proton and neigbouring water molecules, while orbital‐energy shifts measure the strength of the extended electric field of the proton. Abstract : Oxygen K‐edge spectroscopy of hydrated proton complexes in solution provides compelling evidence of the pronounced impact on the electronic structure of the water molecules participating in the hydration, with a hierarchy in coupling strengths of the proton with profoundly strong orbital interactions for the inner three water molecules, and Coulombic field effects of the proton positive charge with the first hydration shell water molecules.