Kumar, M.; Kumar, A.; Pandey, S. Effective Recognition of Lithium Salt in (Choline Chloride: Glycerol) Deep Eutectic Solvent by Reichardt’s Betaine Dye 33. Liquids2023, 3, 393-401.
Kumar, M.; Kumar, A.; Pandey, S. Effective Recognition of Lithium Salt in (Choline Chloride: Glycerol) Deep Eutectic Solvent by Reichardt’s Betaine Dye 33. Liquids 2023, 3, 393-401.
Kumar, M.; Kumar, A.; Pandey, S. Effective Recognition of Lithium Salt in (Choline Chloride: Glycerol) Deep Eutectic Solvent by Reichardt’s Betaine Dye 33. Liquids2023, 3, 393-401.
Kumar, M.; Kumar, A.; Pandey, S. Effective Recognition of Lithium Salt in (Choline Chloride: Glycerol) Deep Eutectic Solvent by Reichardt’s Betaine Dye 33. Liquids 2023, 3, 393-401.
Abstract
Deep eutectic solvents (DESs) have emerged as novel alternatives to common solvents and VOCs. Their employment as electrolytes in battery has been an area of intense research. In this context, understanding changes in physicochemical properties of DESs in the presence of Li salts becomes of utmost importance. Solvatochromic probes have potential to gauze such changes. It is reported herein that one such uv-vis molecular absorbance probe, Reichardt’s betaine dye 33, effectively manifests changes taking place in a DES Glyceline, composed of H-bond accepting salt choline chloride and H-bond donor glycerol in 1 : 2 molar ratio, as salt LiCl is added. Lowest energy intramolecular charge-transfer absorbance band of this dye exhibits 17 nm hypsochromic shift as up to 3.0 molal LiCl is added to Glyceline. The estimated ETN parameter shows linear increase with LiCl mole fraction. Spectroscopic responses of betaine dye 33, N,N-diethyl-4-nitroaniline and 4-nitroaniline are used to assess empirical Kamlet-Taft parameters of dipolarity/polarizability (π*), H-bond donating acidity (α) and H-bond accepting basicity (β) as a function of LiCl concentration in Glyceline. LiCl addition to Glyceline results in increase in α and no change in π*and β. It is proposed that added lithium interacts with oxygen of the –OH functionalities on the glycerol rendering the solvent with increased H-bond donating acidity. It is observed that pyrene, a popular fluorescence probe of solvent polarity, does respond to the addition of LiCl to Glyceline, however, the change in pyrene response starts to become noticeable only at higher LiCl concentration (mLiCl ≥ 1.5 m). Reichardt’s betaine dye is found to be highly sensitive and versatile in gauzing physicochemical properties of DESs in the presence of LiCl.
Chemistry and Materials Science, Physical Chemistry
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