Understanding Differential Interaction of Protic and Aprotic Ionic Liquids inside Molecular Confinement

Abstract

Considering the contemporary interests of water-free reverse micelles (RMs) in the field of organic reaction medium and potential drug delivery carrier, we synthesized two different classes of ionic liquids (ILs), protic N-methyl-2-pyrrolidonium hexanoate, [NMP][Hex], and aprotic choline hexanoate, [Chl][Hex], and subsequently incorporated them in a mixture of polyoxyethylene (20) sorbitan monooleate (Tween-80) and cyclohexane. In order to understand the differential nature of interinterionic interaction of two ILs, we performed DFT calculations on pure ILs to correlate with experimental results. The formation of IL-in-oil RMs was confirmed from phase behavior and DLS studies. Interestingly, [NMP][Hex]-based systems showed a larger monophasic region and droplet size along with higher shear viscosity compared to [Chl][Hex]-based systems. Stronger interaction between [NMP] and Tween-80 due to their protic nature might be the driving force for such observations which supported the resonance stabilization energy [E] and charge population analysis by NBO calculation. Smaller E values along with lesser NBO charges on atoms involved in H-bonding in pure [NMP][Hex] than [Chl][Hex] corroborated with the experimental observations. This primary hypothesis was further confirmed from FTIR and time-resolved fluorescence studies. These systems showed efficient thermal stability. Taking all of the results together, we anticipate that these RMs could be used as efficient delivery systems and for nanomaterial synthesis.

Environmental Aspects of Ionic Liquids in Enhanced Oil Recovery: An Overview

“…From another aspect, according to Bronsted's acid-base theory, PIL are produced from proton transfer from acid to base. [18] Usually, an IL is composed of an organic cation, which may include one or more substituted alkyl chains [R = [CH3(CH2)]nC (nC (carbon number)= 8-20)]; and an organic or inorganic anion. As an illustration, one has alkyl imidazolium [R 1 R 2 mim] + or tetraalkylammonium [NR4] + , associated with tetrafluoroborate (BF4)or chlorine (Cl) -(Fig.…”

Extended H-Bonding through Protic Ionic Liquids Facilitates the Growth and Stability of Water Domains in Hydrophobic Environment

“…Crosio et al showed that certain bimolecular nucleophilic substitution reactions (S N 2) can be promoted in the confined environment of EAN/benzyl- n -hexadecyl­dimethyl­ammonium chloride/toluene-based RM systems . Although Kusano et al and Panda et al have compared the properties of protic and aprotic IL-based water-in-IL and IL-in-oil microemulsions, respectively, the delicate microenvironment and the role of H-bonding in the observed superiority of the protic IL-based systems were overlooked.…”

“…33 Crosio et al showed that certain bimolecular nucleophilic substitution reactions (S N 2) can be promoted in the confined environment of EAN/benzyln-hexadecyldimethylammonium chloride/toluene-based RM systems. 34 Although Kusano et al 35 and Panda et al 36 Synthesis of Ionic Liquids (ILs) and Characterization. We have synthesized protic IL, 1,1,3,3-tetramethylguanidinium salicylate ([TMG][Sal]) and aprotic IL, cholinium salicylate [CHO][Sal] by neutralization of 1,1,3,3-tetramethylguanidine (TMG) and cholinium hydroxide (CHO), respectively, with salicylic acid (Figure S2).…”

A review on tribological performance of ionic liquids as additives to bio lubricants

“…They have the ability to accept and donate a proton and form an extended 3D structure. 73 Phosphonium and pyridinium based ionic liquids are referred as PIL’s. 71 PIL’s have comparatively low cost and are easy to synthesize according to the application.…”