pK_a Scale for Cyclopropenium Ions with Applications in CO₂ Capture

Area of Science:

• Physical Organic Chemistry
• Computational Chemistry
• Materials Science

Background:

• Molecular acid-base properties are fundamental to chemical reactivity prediction.
• Cyclopropenium ions are versatile compounds used as catalysts, ligands, and in redox-flow batteries and materials science.
• Understanding the acidity of cyclopropenium ions is crucial for optimizing their applications.

Purpose of the Study:

• To conduct the first comprehensive computational investigation of pKa values for a diverse set of cyclopropenium ions.
• To explore the application of a cyclopropenium-based platform for carbon dioxide (CO2) capture and light-triggered release.

Main Methods:

• Utilized density functional computations to determine pKa values for 70 structurally distinct cyclopropenium derivatives.
• Employed Hammett linear free-energy relationships to analyze structure-acidity correlations.
• Investigated a cyclopropenium-cyclopropenylidene coupled system for CO2 capture.

Main Results:

• Established a comprehensive dataset of computed pKa values for a wide range of cyclopropenium ions.
• Demonstrated the utility of Hammett relationships in understanding the acidity of these systems.
• Showcased a novel platform for effective CO2 capture and controlled release.

Conclusions:

• The computational study provides critical insights into the acid-base properties of cyclopropenium ions.
• The findings facilitate the rational design of cyclopropenium derivatives for various applications.
• The developed platform offers a promising approach for greenhouse gas management.