Reactions of Hydrated Electrons (H₂O)_n⁻ with Carbon Dioxide and Molecular Oxygen: Hydration of the CO₂⁻ and O₂⁻ Ions

Abstract

The gas-phase reactions of hydrated electrons with carbon dioxide and molecular oxygen were studied by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Both CO2 and O2 react efficiently with (H2O)n- because they possess low-lying empty pi* orbitals. The molecular CO2- and O2- anions are concurrently solvated and stabilized by the water ligands to form CO2(-)(H2O)n and O2(-)(H2O)n. Core exchange reactions are also observed, in which CO2(-)(H2O)n is transformed into O2(-)(H2O)n upon collision with O2. This is in agreement with the prediction based on density functional theory calculations that O2(-)(H2O)n clusters are thermodynamically favored with respect to CO2(-)(H2O)n. Electron detachment from the product species is only observed for CO2(-)(H2O)2, in agreement with the calculated electron affinities and solvation energies.

Reduction of Acetonitrile by Hydrated Magnesium Cations Mg+(H2O)n (n≈20–60) in the Gas Phase

“…As shown previously for HCl, O 2 , and CO 2 , [10,22,23,39] this reflects the reactivity of the hydrated electron (H 2 O) n À , which in collisions with acetonitrile reacts to form OH À (H 2 O) m . [25] In principle, uptake of CH 3 CN could also trigger the formation and elimination of a hydrogen atom, but the required selective evaporation of CH 3 CN to rationalize the exclusive formation of MgOH + (H 2 O) m is, in view of the high efficiency of reaction (2), highly improbable.…”

“…[7] Quantum chemical calculations corroborate the interpretation of the experiments [7,9] that for n > 14, Mg + (H 2 O) n consist of a doubly charged magnesium ion and a hydrated electron, with the spin density of the system distributed in a site remote from the metal center. [13,21,22] In a combined experimental and theoretical study, we were able to show that Mg + (H 2 O) n also exhibit the chemistry of the hydrated electron [23,24] in reactions with O 2 and CO 2 , albeit with significantly reduced reaction efficiencies. [22] In the uptake of O 2 or CO 2 , the hydrated electron is scavenged by the reactant, and formation of MgOH + does not occur.…”

Collision-Induced Dissociation Study of Strong Hydrogen-Bonded Cluster Ions Y⁻(HF)<i>_n</i> (Y=F, O₂) Using Atmospheric Pressure Corona Discharge Ionization Mass Spectrometry Combined with a HF Generator

“…e peak corresponding to the uoride ion F − was also absent in the CID spectrum of F − (HF) 3 (Fig. 3c), suggesting an insu cient internal energy of the precursor ion F − (HF) 3 . With regard to this, the internal energy deposited in the precursor ions can be roughly estimated from the E CM .…”

“…e estimated energy was consistent with the E CM value of 1.99 eV reported by Wenthold and Squires. 6) On the other hand, the E CM data for F − (HF) 2 and F − (HF) 3 showed that the rst loss of HF from these precursor ions occurred at 1 eV/E CM or lower to form the product ions F − (HF) and F − (HF) 2 , respectively (Figs. 4b and 4c).…”

“…Mass spectrometry (MS) provides data on the hydrogen bond dissociation characteristics of complex gaseous ions such as hydrated cluster ions H 3 O + (H 2 O) n and Y − (H 2 O) n (Y=OH, O 2 , CO 2 ), [1][2][3] and it also gives experimental evidence of the thermodynamic stabilities of small clusters. 4,5) Although it is di cult to apply the collision-induced dissociation (CID) method to weakly bound hydrogen-bonded systems, it is possible to use it to examine strong hydrogenbonded systems such as the uoride ion complex F − (HF).…”