Solvent Organization and Electrostatics Tuned by Solute Electronic Structure: Amide versus Non-Amide Carbonyls

Area of Science:

• Physical Chemistry
• Chemical Physics
• Spectroscopy

Background:

• Vibrational Stark effect uses carbonyl groups to measure electric fields in reactive environments.
• Previous research focused on solvent's role in tuning electric fields on solutes.

Purpose of the Study:

• To investigate the role of solute electronic structure in modifying local solvent organization and electric fields.
• To understand how amides and other carbonyl-containing molecules interact with solvents.

Main Methods:

• Infrared absorption spectroscopy of amide and non-amide carbonyls in various solvents.
• Vibrational Stark spectroscopy.
• Molecular dynamics simulations.
• Electronic structure calculations.

Main Results:

• Amide-containing molecules show distinct frequency shifts in polar solvents compared to non-amide carbonyls.
• Larger frequency shifts in amides are due to stronger p-π conjugation, increasing C═O bond dipole moments and inducing solvent organization.
• Both first solvation shell and bulk solvent contributions significantly impact electric fields, increasing with solute conjugation.

Conclusions:

• Solute structure is crucial for tuning solvent organization and the local electrostatic environment.
• A solute-centric approach is vital for designing electrostatic environments in condensed-phase chemical processes.