Interpreting the physiochemical properties and structure-property correlations of ionic liquids (ILs) is a key to the enlargement of their optimized structures for specific applications. In this work, a series of ILs based on 1-alkyl-1,2,4-triazolium cation with trifluoromethanesulfonate anion were synthesized and the effect of cation and temperature on physiochemical properties such as density, viscosity, speed of sound, conductivity, and rheology was studied. Temperature dependence densities were correlated with the densities estimated by the Gardas and Coutinho model, whereas viscosity and molar conductivity have been found to satisfy the Vogel-Tammann-Fulcher (VTF) equation over the studied temperature range 293.15-343.15 K. Further, to explore the wide range of applications, ionicity has been tested by correlating the fluidity with molar conductivity and it was found that synthesized ILs can be referred to as "good ILs". Furthermore, the fluidity behavior describing the interactions between the cation and anion of ILs was investigated through their rheological properties, and the Newtonian behavior of ILs has been examined by varying the effect of shear rate on viscosity. Finally, the impact of structure variants in terms of the N-1 functionalized 1,2,4-triazole ring has been analyzed over the studied properties.

Performing biocatalysis in nonaqueous solvents is advantageous as it imparts enhanced solubility to hydrophobic substrates and an ability to increase the temperature for shifting reaction equilibrium in the forward direction. In this work, we show the design and development of another class of nonaqueous composite solvent obtained by mixing surface modified enzyme and neat ionic liquid (IL). We systematically probe the interaction and solubility of industrially relevant α-chymotrypsin in its native or surface-bound polymer–surfactant bioconjugated form, with neat protic (N-methyl-2-pyrrolidonium trifluoromethanesulfonate; [NMP]­[OTf]), or aprotic (1-methyl-3-(4-sulfobutyl)-1H-imidazol-3-ium trifluoromethanesulfonate; [HO 3 S­(CH 2 ) 4 MIm]­[OTf]), ILs. Polarized optical micrographs show that the lyophilized powder of native α-chymotrypsin, nCT, does not disperse in either of the neat ILs, however, its polymer surfactant (PS)-coated bioconjugate counterparts, PScCT, in the waterless state, can be well-dispersed and solubilized in the neat [HO 3 S­(CH 2 ) 4 MIm]­[OTf]. The solubilization of waterless bioconjugates of PScCT in neat aprotic IL provides a composite liquid, WL-ImPScCT (WL: waterless, Im: [HO 3 S­(CH 2 ) 4 MIm]­[OTf]), having a viscosity of 69.6 Pa·s at 25 °C with a shear-thinning behavior, ≈ 15 w/w % α-chymotrypsin, and ≈ 1.2 w/w % residual water content. Detailed secondary structural analysis using circular dichroism and Fourier self-deconvolution on the ATR-FTIR data of WL-ImPScCT liquid reveals retention of the near native secondary structure of α-chymotrypsin. Further, using a combination of fluorescence spectroscopy and electron spray ionization mass spectrometry, we show that scattering of dry and powdered bovine serum albumin (BSA) protein on the WL-ImPScCT composite liquid results in the solubilization of the former, followed by limited proteolysis of BSA by the α-chymotrypsin. Our results, therefore, show the stabilization of α-chymotrypsin in a neat aprotic IL environment to yield a composite liquid, which not only acts as a nonaqueous, nonvolatile, and environmentally benign solvent, but also provides a biocatalytic platform capable of carrying out reactions relevant for biotransformations, food processing, drug delivery, and various other applications.

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In search of better replacement for highly polar volatile organic solvents, ionic liquids (ILs) with high polarity and high polarizability were synthesized using N‐1 substituted 1,2,4‐triazolium‐based cation with trifluoromethanesulfonate as the counter anion. The temperature dependence polarity of the synthesized ILs has been investigated using solvatochromic dyes and expressed in terms of and Kamlet‐Taft parameters (dipolarity/polarizability (π*), hydrogen bond donor acidity (α), and hydrogen bond basicity (β) in the range of (293.15−353.15) K. The introduction of the –SO3H functional group and triazole ring on the cation has revealed high polarity (ETN >1.2) and high polarizability (π*> 3.2). Furthermore, to understand the extent of intermolecular interaction temperature dependence refractive indices have been measured in the temperature range (293.15−343.15) K and a positive correlation was observed with polarity parameter. Finally, the impact of structure variants in terms of the N‐1 functionalized 1,2,4‐triazole ring has been analyzed over the studied properties which is scrutinized to understand the solvation capability and intermolecular interaction in ILs.