Preferential Ion Microsolvation in Mixed-Modifier Environments Observed Using Differential Mobility Spectrometry.

Area of Science:

• Physical Chemistry
• Chemical Physics
• Analytical Chemistry

Background:

• Understanding preferential solvation is crucial for interpreting ion-molecule interactions in complex gas-phase environments.
• Differential Mobility Spectrometry coupled with Mass Spectrometry (DMS-MS) is a powerful tool for studying these interactions.
• Protonated quinoline derivatives serve as model systems for investigating cation solvation.

Purpose of the Study:

• To measure the preferential solvation behavior of eight protonated quinoline derivatives.
• To investigate the influence of binary solvent mixtures on ion-solvent cluster formation.
• To correlate experimental observations with theoretical calculations of ion-solvent binding energies.

Main Methods:

• Tandem differential mobility spectrometer mass spectrometer (DMS-MS) was employed to study ion-solvent interactions.
• Ion-solvent cluster formation was induced by introducing solvent vapors (water, acetonitrile, isopropyl alcohol) into the N2 buffer gas.
• Density Functional Theory (DFT) calculations were performed to determine ion-solvent binding energies.

Main Results:

• Doping the buffer gas with binary solvent mixtures resulted in preferential binding of quinolinium ions to one modifier over another.
• Experimental data indicated that quinolinium ions exclusively bind to the solvent with which they exhibit the strongest interaction.
• DFT calculations confirmed that acetonitrile had the strongest binding energy, followed by isopropyl alcohol, and then water.

Conclusions:

• The binding of protonated quinoline ions in mixed solvent vapors is governed by the intrinsic ion-solvent binding strength.
• The presence of other solvent modifiers does not alter the exclusive binding preference of the ions.
• These findings provide fundamental insights into selective solvation phenomena in complex chemical systems.