From a localized H3O radical to a delocalized H3O+···e- solvent-separated pair by sequential hydration

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Quantum Chemistry

Background:

• The H(3)O moiety exists as a radical in the gas phase, prone to decomposition.
• Understanding microhydration effects is crucial for solvation studies.

Purpose of the Study:

• To investigate the impact of microhydration on H(3)O's electronic structure and reactivity.
• To elucidate the transition from radical to ion-pair behavior upon solvation.

Main Methods:

• Ab initio calculations were employed to model the H(3)O system.
• Electronic structure and spin density distribution were analyzed.

Main Results:

• Gas-phase H(3)O is a kinetically stable radical with localized spin density.
• Solvation by one water molecule retains radical character.
• Solvation by two or three water molecules shifts spin density, forming a hydronium cation and hydrated electron pair.

Conclusions:

• Microhydration dramatically influences H(3)O's electronic properties and reactivity.
• The H(3)O system transitions to a solvent-separated ion pair with increasing solvation.
• This behavior resembles proton-electron pairing in bulk water.