# Do Dipolar Cosolvents Mitigate Microheterogeneity in Deep Eutectic Solvents? Solvation Dynamics and Solute Rotations in Glyceline/Methanol Solutions

## TL;DR

This study uses fluorescence techniques to explore how solutes behave in mixtures of methanol and glyceline, a deep eutectic solvent.

## Contribution

The study reveals solvation dynamics and rotational behavior of solutes in glyceline/methanol mixtures, highlighting preferential solvation effects.

## Key findings

- Solvation dynamics of C153 and C343 in glyceline/methanol mixtures are biexponential with similar integral solvation times.
- Solute rotational dynamics are single exponential but not viscosity-dependent, indicating preferential solvation by glyceline components.

## Abstract

Steady-state and
time-resolved fluorescence was used to investigate
the solvation and rotational dynamics of coumarin 153 (C153) and coumarin
343 (C343) in binary solutions of methanol and glyceline, a deep eutectic
solvent (DES) composed of a 1:2 molar ratio of choline chloride and
glycerol. Time-resolved Stokes shifts were used to quantify the solvation
dynamics and were found to be biexponential for both C153 and C343
with nearly identical integral solvation times. The solvation times
were also found to be weakly dependent upon solution viscosity, and
a power law exponent of p = 0.18 was found for mole
fractions of glyceline greater than x
DES = 0.2. Solute rotational dynamics were explored using time-resolved
fluorescence anisotropy. The reorientation times of C153 and C343
were found to be single exponential at all mixture compositions but
did not follow a power-law dependence on solution viscosity. Instead,
there was evidence for preferential solvation of the probes by components
of glyceline.