Temperature-Dependent Solvatochromic Probe Behavior within Ionic Liquids and (Ionic Liquid + Water) Mixtures

Abstract

Spectroscopic responses of absorbance probes, betaine dye 33, N,N-diethyl-4-nitroaniline, and 4-nitroaniline, and fluorescence dipolarity probes, pyrene (Py) and pyrene-1-carboxaldehyde (PyCHO) within ionic liquids (ILs) 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), and aqueous mixtures of [bmim][BF4] are used to assess the changes in important physicochemical properties with temperature in the range 10-90 degrees C. ETN obtained from betaine dye 33, indicating dipolarity/polarizability and/or hydrogen bond donating (HBD) acidity, decreases linearly with increasing temperature within the two ILs. Changes in Kamlet-Taft parameters dipolarity/polarizability (pi*), HBD acidity (alpha), and HB accepting (HBA) basicity (beta) with temperature show interesting trends. While pi* and alpha decrease linearly with increasing temperature within the two ILs, beta appears to be independent of the temperature. Similar to ETNand pi*, the first-to-third band intensity ratio of probe Py also decreases linearly with increasing temperature within the ILs. The lowest energy fluorescence maxima of PyCHO, though it decreases significantly within water as the temperature is increased from 10 to 90 degrees C, it does not change within the two ILs investigated. The temperature dependence of the dipolarity/polarizability as manifested via betaine dye 33 behavior is found to be more within the aqueous mixtures of [bmim][BF4] as compared to that within neat [bmim][BF4] or neat water. The sensitivity of pi* toward temperature increases as IL is added to water and that of alpha decreases. The temperature dependent Py behavior shows no clear-cut trend within aqueous mixtures of [bmim][BF4]; insensitivity of the PyCHO response toward temperature change is reasserted within aqueous IL mixtures. All-in-all, the temperature-dependent behavior of solvatochromic probes within [bmim][PF6], [bmim][BF4], and aqueous mixtures of [bmim][BF4] is found to depend on the identity of the probe.

Temperature‐Responsive Low Molecular Weight Ionic Liquid Based Gelator: An Approach to Fabricate an Anti‐Cancer Drug‐Loaded Hybrid Ionogel

“…The self-assembly behaviour of CetPySal in aqueous medium was performed using multi technique approach. [32][33][34][35][36]48] Surface active and micellization parameters derived from the surface tension and conductivity measurements are reported in Table 1 and are compared with precursor surfactant CPCl. [48] Plots of surface tension and specific conductivity (k) versus [CetPySal] are shown in Figure 1.…”

“…Our group is engaged in designing various amphiphilic molecules for their tailor made interfacial and micellar properties, ionic liquid based surfactants (ILBS) with better surface active and micellar properties than the traditional surfactants are one of them. [30][31][32][33][34][35][36] Herein we had designed salicylate based IL (Figure 1a), cetylpyridinium salicylate (CetPySal) that show better surface active and micellar properties than its precursor surfactant cetylpyridinium chloride (CPCl) and exhibited temperature responsive gel-to-gel phase transition. The cationic precursors of the CetPySal, CPCl is known for the antiseptic and antibacterial activity as well as have applications in various fields including mouthwashes, toothpastes and in various pharmaceutical formulations among others.…”

Room temperature ionic liquids as emerging solvents for the pretreatment of lignocellulosic biomass

“…The Kamlet-Taft parameters (a, b, and p à ) are temperature-dependent solvent polarity scales (Lee and Prausnitz, 2010;Trivedi et al, 2010) and similar as described for Abraham equation. For RTILs, Kamlet-Taft parameters can be easily measured by uv/vis spectroscopy in the presence of solvatochromic dyes; the most common being Reichardt's dye (RD), N,N-diethyl-4-nitroaniline (DENA), and 4-nitroaniline (4NA).…”

Interaction Between Ionic Liquids and Gemini Surfactant: A Detailed Investigation into the Role of Ionic Liquids in Modifying Properties of Aqueous Gemini Surfactant

“…Comprehensive studies on the interactions between mixtures of gemini and conventional single chain surfactants of different charge classes to form mixed micellar aggregates have been reported [31][32][33][34]. In recent decades, studies on the interactions between single chain surfactants and IL have been reported and the results obtained are discussed at length [35][36][37][38][39][40][41][42][43][44][45][46]. Pandey et al [35][36][37][38] reported the dual behavior of IL in aqueous solutions of single chain surfactants.…”