Neighboring Alkali Cations as an Efficient Strategy for N₂ Activation: A DFT Analysis

Area of Science:

• Inorganic Chemistry
• Computational Chemistry
• Catalysis

Background:

• Nitrogen gas (N2) is abundant but challenging to activate, limiting its industrial and biological applications.
• Microbial nitrogen fixation is efficient but difficult to replicate synthetically.
• Metal-organic approaches are explored, with increasing interest in non-covalent interactions for catalysis.

Purpose of the Study:

• To investigate the influence of alkali and alkaline-earth cations on dinitrogen (N2) activation.
• To understand the role of ionic interactions in enhancing N2 activation mechanisms.
• To identify specific cations and conditions that promote efficient N2 activation.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• The effect of various cations (M^n+) on N2 was studied at distances from 2 to 10 Å.
• Analysis focused on polarization, electrostatic interactions, and electron delocalization.

Main Results:

• Three distinct activity regimes were identified based on cation-N2 interactions.
• Regime I: Polarization of N2 is dominant.
• Regime III: Electrostatic interactions and electron delocalization are key, with Group II-A cations showing high potential.
• Magnesium ion (Mg2+) exhibited exceptional activity at a distance of 2.7 Å.

Conclusions:

• Ionic interactions, particularly from Group II-A cations like Mg2+, significantly enhance dinitrogen activation.
• DFT calculations reveal distinct mechanisms governing N2 activation by cations.
• These findings provide a theoretical basis for designing synergistic catalysts combining covalent and non-covalent interactions for efficient N2 activation.