C-H···π interactions disrupt electrostatic interactions between non-aqueous electrolytes to increase solubility.

Area of Science:

• Electrochemistry
• Materials Science
• Organic Chemistry

Background:

• Grid-scale energy storage relies on soluble redox-active organic molecules, like those in redox flow batteries.
• Pyridinium salts offer stable redox properties but suffer from low solubility in non-aqueous solvents.
• Existing molecular design strategies to enhance solubility are limited.

Purpose of the Study:

• To investigate the role of C-H···π interactions in determining the solubility of N-substituted pyridinium salts.
• To establish a correlation between the number of C-H···π interactions and pyridinium salt solubility in acetonitrile.
• To demonstrate a practical molecular design approach for improving solubility in non-aqueous media.

Main Methods:

• Synthesized and characterized various N-substituted pyridinium salts.
• Quantified the number of C-H···π interactions for each pyridinium salt.
• Measured the solubility of pyridinium salts in acetonitrile.
• Correlated the number of C-H···π interactions with measured solubility data.

Main Results:

• A direct correlation was observed between the number of C-H···π interactions and pyridinium salt solubility in acetonitrile.
• Increased C-H···π interactions led to significantly higher solubility.
• This highlights the impact of weak dispersion interactions in overcoming strong electrostatic forces.

Conclusions:

• C-H···π interactions are a key factor governing the solubility of pyridinium salts in non-aqueous solvents.
• This finding provides a valuable molecular design principle for enhancing solubility in energy storage materials.
• Minimal structural modifications focusing on C-H···π interactions can dramatically improve pyridinium salt solubility.