60 Years of Betaine 30─From Solvatochromic Discovery to Future Frontiers.

Betaine-30 (B30) was reported by Karl Dimroth and Christian Reichardt et al. in 1963 as a solvatochromic probe that can be easily synthesized, shows good solubility, and remains stable in various organic solvents and solutions. Its strongly negatively solvatochromic behavior arises from differential solvation between its electronic ground and excited states, making it a valuable tool for assessing solvent polarity using the (30) polarity scale, also devised by Dimroth and Reichardt.

Unusual Hydration Properties of Choline Fluoride-Based Deep Eutectic Solvents.

The hydration properties of the fluoride-based deep eutectic solvent ethalineF [a solution of choline fluoride in ethylene glycol (EG) at a 1:2 molar ratio] are studied and compared to the most common deep eutectic solvent ethaline (the solution of choline chloride in EG at 1:2 molar ratio). The densities of the deep eutectic solvent (DES) based on choline fluoride in EG (ethalineF) and its mixtures with water as cosolvent are measured over the temperature range of 298-323 K. The excess properties, including excess molar volumes, excess partial molar volumes, and viscosity deviations from ideal behavior, are calculated for ethalineF/water and ethaline/water mixtures and compared.

Enhanced Dynamics and Charge Transport at the Eutectic Point: A New Paradigm for the Use of Deep Eutectic Solvent Systems.

Deep eutectic solvents (DESs) are a class of versatile solvents with promise for a wide range of applications, from separation processes to electrochemical energy storage technologies. A fundamental understanding of the correlation among the structure, thermodynamics, and dynamics of these materials necessary for targeted rational design for specific applications is still nascent. Here, we employ differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS), and femtosecond transient absorption spectroscopy (fs-TAS) to investigate the correlation among thermodynamics, dynamics, and charge transport in mixtures comprising a wide range of compositions of choline chloride (ChCl) and ethylene glycol (EG).

Redox-Active Eutectic Electrolyte with Viologen and Ferrocene Derivatives for Flow Batteries.

Nonflammable eutectic solvents show great potential to enhance the concentrations of the redox-active materials and the cell voltages for redox flow batteries (RFBs). Herein, we report a promising redox-active eutectic electrolyte (1.5 M total redox species) with viologen and ferrocene derivatives where both of the redox reactions are reversible with a maximum open-circuit voltage of 1.

Solvation Dynamics of Wet Ethaline: Water is the Magic Component.

The past two decades witnessed the development of a new type of solvent system, named deep eutectic solvents, which have become increasingly investigated because they offer new and potentially favorable properties, such as wide tunability in electrochemical, mechanical, and transport properties. Deep eutectic solvent (DES) systems are composed of at least one main solvent and an additional component that is meant to interrupt the original solvent/solvent interactions, thereby introducing lower melting points relative to each individual component. Ethaline (a 1:2 mol % mixture of choline chloride and ethylene glycol) is one of the most promising DES systems.

Structural Characterization of Thermochromic and Spin Equilibria in Solid-State Ni(detu)4Cl2 (detu = N,N'-Diethylthiourea).

Consecutive thermochromic lattice distortional and spin crossover equilibria in solid-state Ni(detu)4Cl2 (detu = N,N'-diethylthiourea) are investigated by variable-temperature X-ray crystallography (173-333 K), DFT calculations, and differential scanning calorimetry. Thermochromism and anomalous magnetism were reported previously (S. L.