Electron transfer controlled by hydrogen bond donor/acceptor exchange in [H2O]6

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Quantum Dynamics

Background:

• Anionic water clusters are crucial in atmospheric and condensed-phase chemistry.
• Understanding charge localization and transfer is key to describing reactivity.
• The H2O6- cluster presents a model system for studying excess electron behavior.

Purpose of the Study:

• To investigate the dynamics of hydrogen bond exchange in the H2O6- cluster.
• To characterize the role of quantum fluctuations and proton tunneling.
• To analyze the spatial distribution of the excess electron during the reaction.

Main Methods:

• Path Integral Molecular Dynamics (PIMD) simulations.
• Cryogenic conditions to stabilize the cluster.
• Analysis of reactive pathways, charge localization, and free-energy profiles.

Main Results:

• Geared rotations of water molecules drive charge reorganization.
• Excess electron delocalizes across both water molecules at transition states.
• Quantum fluctuations introduce a plateau in the free-energy profile, indicating proton tunneling.
• Reduced vertical detachment energies at reactant/product states and increased at transition states due to quantum effects.

Conclusions:

• Proton tunneling significantly impacts the H2O6- reaction dynamics and electron solvation.
• Quantum nuclear effects are essential for accurately describing the electron's behavior and the reaction energetics.
• The study provides insights into electron-proton-nuclear coupling in anionic water clusters.