Twisted Eigen Can Induce Proton Transfer at a Hydrophobic-Hydrophilic Interface

Area of Science:

• Chemical Science
• Materials Science
• Physical Chemistry

Background:

• Proton localization at interfaces is crucial for chemical and materials science.
• Understanding interfacial proton transfer mechanisms is essential for various applications.

Purpose of the Study:

• To investigate proton localization and transfer at hydrophobic-hydrophilic interfaces.
• To model protonated benzene (benzenium ion) and water clusters [BZH+Wn, n=1-6].
• To elucidate the role of noncovalent interactions in stabilizing these protonated species.

Main Methods:

• Utilized *ab initio* (MP2) and density functional theory (B3LYP) methods.
• Calculated geometries, energetics, and spectral signatures of protonated species.
• Analyzed interfacial interactions and proton transfer mechanisms.

Main Results:

• Identified novel low-lying isomers of protonated species at interfaces.
• Proton localization in hydrophilic environments is more stable than on hydrophobic benzene π-clouds.
• O-H+···π hydrogen bonds significantly influence O-H+···O interactions and vibrational modes of the Eigen cation.
• Aromatic π-clouds stabilize the Eigen cation, and twisted forms enhance Grotthuss-type proton transfer.
• Vibrational spectra show significant red-shifted frequencies for O-H+···O, O-H+···π, and O-H···π interactions.

Conclusions:

• Proton localization at hydrophobic-hydrophilic interfaces is governed by a balance of interactions.
• Aromatic π-clouds play a dual role in stabilizing protonated species and facilitating proton transfer.
• Computational methods (B3LYP) provide results in good agreement with higher-level methods (MP2) and experimental data.