Simulating Electron Transfer Reactions in Solution: Radical-Polar Crossover.

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Organic Chemistry

Background:

• Single-electron transfer (SET) reactions drive diverse chemical transformations.
• Accurate modeling of SET requires careful consideration of electronic and solvent effects.
• Existing methods may not fully capture the nuances of SET mechanisms.

Purpose of the Study:

• Introduce a novel computational tool for modeling SET-initiated reactions.
• Investigate reaction mechanisms of organic electron donors tetrakis(dimethylamino)ethylene (TDAE) and tetrathiafulvalene (TTF).
• Elucidate the role of solvent environments in SET kinetics and thermodynamics.

Main Methods:

• Development and application of a combined constrained density functional theory and molecular mechanics (CDFT/MM) approach.
• Mechanistic analysis of radical-polar crossover reactions involving TDAE and TTF.
• Examination of solvent effects on reaction pathways and energetics.

Main Results:

• Identification of an unexpected tertiary radical intermediate in the TDAE system.
• Explanation of structure-kinetics relationships in the TTF system.
• Quantification of significant solvent impact on SET reaction energetics (>20 kcal/mol free energy difference).

Conclusions:

• The new CDFT/MM tool provides valuable mechanistic insights into SET reactions.
• Solvent dynamics are critical for accurate quantification of SET kinetics and thermodynamics.
• The method is well-suited for studying condensed-phase SET reactions.