Isomerization-assisted proton transfers in MeOH-(H2O)2H.

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Chemical Physics

Background:

• Proton transfer in small clusters is fundamental to many chemical and biological processes.
• Understanding isomerization dynamics is key to elucidating reaction mechanisms.

Purpose of the Study:

• To investigate the microscopic properties and free energy landscapes of two isomerization processes in the MeOH(H2O)2H+ trimer.
• To characterize the role of proton migration and its impact on cluster topology and dynamics.

Main Methods:

• Path Integral Molecular Dynamics (PIMD) simulations at T = 50 K.
• Calculation of free energies along reversible paths using order parameters.
• Analysis of proton behavior and potential energy surface characteristics.

Main Results:

• Two distinct isomerization pathways were identified, one altering cluster topology from branched to chain-like.
• Concomitant migration of the excess proton was observed in both isomerizations.
• Compact, stable structures of the proton were found, suggesting no significant tunneling contributions.

Conclusions:

• Proton transfer in this system is governed by isomerization dynamics rather than tunneling.
• The observed proton behavior influences the structural evolution of the water-methanol cluster.
• Isomerization rates were estimated, providing insights into the kinetics of these processes.