The Role of the Density Response Kernel in the Protonation Process

Area of Science:

• Quantum Chemistry
• Theoretical Chemistry
• Chemical Reactivity

Background:

• Protonation of Lewis bases causes significant electron distribution changes.
• Perturbative models and density functional theory (DFT) are used to describe these electronic property shifts.
• Proton interactions, like the electric field of a bare nucleus, often require higher-order perturbative terms.

Purpose of the Study:

• To analyze the impact of protonation on the electronic structure of various Lewis bases.
• To identify the primary perturbative term governing protonation site selection.
• To correlate the protonation site with the inherent chemical nature of the Lewis base.

Main Methods:

• Utilizing density functional theory-based reactivity indices.
• Applying perturbative models to quantum mechanical descriptions.
• Analyzing electron density changes upon protonation.

Main Results:

• Protonation effects on Lewis base electronic structure were analyzed.
• The leading perturbative term influencing protonation site was identified.
• A relationship between the protonation site and Lewis base chemical nature was explored.
• Electron redistribution effects were found to be significant, particularly for highly polarizable species, even when electrostatics initially dominate.

Conclusions:

• Perturbative models, especially DFT reactivity indices, are valuable for predicting protonation-induced electronic changes.
• The leading term in perturbation theory helps determine protonation sites, linked to the Lewis base's chemical properties.
• Electron redistribution plays a crucial role in protonation, sometimes outweighing initial electrostatic interactions for polarizable bases.