Spectral study of specific interactions between zwitterionic compounds and protic solvents.

Area of Science:

• Physical Chemistry
• Spectroscopy
• Supramolecular Chemistry

Background:

• Zwitterionic compounds, such as ylids, exhibit unique interactions with protic solvents via universal and specific forces.
• Ylids possess a visible electronic absorption band associated with intramolecular charge transfer (ICT), which is sensitive to solvent properties and indicative of stability.
• Understanding these solute-solvent interactions is crucial for predicting and controlling the behavior of zwitterionic compounds.

Purpose of the Study:

• To investigate the solvatochromic properties of pyridinium dicarbethoxy methylid and iso-quinolinium dicarbethoxy methylid.
• To quantify the contribution of specific solute-solvent interactions to the spectral shift of the visible ICT band in these ylids.
• To estimate differences in interaction energies between ylids and protic versus aprotic solvents using a cell model.

Main Methods:

• Solvatochromic analysis of two specific zwitterionic compounds (ylids).
• Spectroscopic study of the visible intramolecular charge transfer (ICT) band.
• Application of a cell model for ternary solutions to analyze solute-solvent interactions.

Main Results:

• The study established the contribution of specific solute-solvent interactions to the spectral shift of the visible ICT band for the studied ylids.
• Differences in interaction energies between ylid-protic solvent and ylid-aprotic solvent molecular pairs were estimated.
• The solvatochromic behavior provides a method for assessing ylid stability and interaction profiles.

Conclusions:

• Specific solute-solvent interactions significantly influence the spectral properties of zwitterionic compounds.
• The ICT band's sensitivity to solvent polarity can be utilized to probe ylid stability.
• The cell model effectively estimates interaction energy differences in multi-component ylid solutions.