Shruti Trivedi

Temperature-dependent solvatochromic probe behavior within ionic liquids and (ionic liquid + water) mixtures.

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.

Synthesis and properties of L-valine based chiral long alkyl chain appended 1,2,3-triazolium ionic liquids

The increasing importance of ionic liquids (ILs) in various strata of chemical sciences is largely due to the fact that modification in the architecture of the cation and/or the anion imparts favorable and specific properties to an IL. Consequently, there is a need to develop new ILs with different functionalities. A series of L-valine based alkyl chain-appended 1,2,3-triazolium ILs (alkyl = hexyl, octyl, dodecyl, cetyl and octadecyl) with iodide and hexafluorophosphate anions, respectively, are synthesized and characterized. These new ILs show optical activity and hence are termed chiral ILs (CILs). All ten CILs are room temperature ILs (RTILs) as their melting points, obtained from differential scanning calorimetry (DSC), are found to be below ambient temperature. Thermogravimetric analysis indicates these CILs to have adequate thermal stability. The longer alkyl chain containing CILs exhibit facile self-aggregation when dissolved in ethanol. There is a hint of pre-micellar aggregation by short alkyl chain possessing CILs along with the long alkyl chain containing ones. These CILs demonstrate weak absorbance and emission of UV-Vis radiation and hence can be considered ideal solvents for photochemical applications. These CILs, consisting of different functionalities, possess interesting properties and have potential to be used in many areas of chemistry.

Surfactant Self-Assembly Within Ionic-Liquid-Based Aqueous Systems

Ionic liquids (ILs) have received increased attention from both academic and industrial research communities all over the world due to their unusual properties and immense application potential in various fields of science and technology. During the past decade, ionic-liquid-based systems have become the subject of considerable interest as a promising media for extraction and purification of several macro-/biomolecules. ILs are attractive designer solvents with tunable physicochemical properties. Using IL-based systems as alternative solvents for forming surfactant self-assemblies has several advantages. For example, the properties of surfactant self-assemblies in these media can be easily modulated by tuning the structure of ILs; ILs can dissolve a large variety of organic and inorganic substances and their properties are designable to satisfy the requirements of various applications. This may enhance the application potential of both ILs and surfactants in many important fields. Consequently, the study on surfactant self-assemblies within IL-based aqueous systems has attracted considerable attention in recent years. This chapter overviews the investigation carried out on the formation of surfactant self-assemblies within IL-based aqueous systems and their applications in various fields.