# Preferential Solvation of Zwitterionic Benzo-[f]-Quinolinium Ylids in Binary Solvent Mixtures: Spectral Study and Quantum Chemical Calculations

## TL;DR

This study explores how zwitterionic compounds interact with mixed solvents using spectral analysis and quantum calculations.

## Contribution

The paper introduces a new method to analyze solvent-solute interactions using benzo-[f]-quinolinium ylids in binary solvent mixtures.

## Key findings

- The solute was preferentially solvated by polar protic solvent in the mixture.
- Specific solute-solvent interactions led to progressive occupation of the solvation microsphere by protic solvent.
- Binding energy calculations showed the energetic favorability of solute-coordinating solvent complexes.

## Abstract

Three derivatives of benzo-[f]-quinolinium ylids, which all underwent an intermolecular charge transfer process, were used as solvatochromic indicators to study the specific solvent–solute interactions in binary mixtures of protic–aprotic solvents with different molar ratios. The microenvironment around the solute molecules was observed via electronic absorption spectroscopy and was analyzed by employing solvation models and quantum chemical calculations. The spectral analysis suggested that the solute was preferentially solvated by the polar protic solvent, indicating a lack of synergy between the two solvents. The solvation microsphere was progressively occupied by the protic solvent, on the basis of specific solute–solvent interactions. By modeling the 1:2 (solute-coordinating solvent) complexes with explicit solvents, the binding energy for complex formation was estimated.