Toward the Proactive Design of Sustainable Chemicals: Ionic Liquids as a Prime Example

The tailorable and often unique properties of ionic liquids (ILs) drive their implementation into a broad variety of seminal technologies. The modular design of ILs allows in this context a proactive selection of structures that favor environmental sustainability─ideally without compromising their technological performance. To achieve this objective, the whole life cycle must be taken into account and various aspects considered simultaneously. In this review, we discuss how the structural design of ILs affects their environmental impacts throughout all stages of their life cycles and scrutinize the available data in order to point out knowledge gaps that need further research activities. The design of more sustainable ILs starts with the selection of the most beneficial precursors and synthesis routes, takes their technical properties and application specific performance into due account, and considers its environmental fate particularly in terms of their (eco)toxicity, biotic and abiotic degradability, mobility, and bioaccumulation potential. Special emphasis is placed on reported structure-activity relationships and suggested mechanisms on a molecular level that might rationalize the empirically found design criteria.

Facile Synthesis of Tetra-Branched Tetraimidazolium and Tetrapyrrolidinium Ionic Liquids

A facile synthetic route for tetra-branched tetraimidazolium and tetrapyrrolidinium ionic liquids was developed. In contrast to the previous synthetic scheme, the new synthetic route requires only three reaction steps instead of seven. The total yield of tetracation was also improved from 17-21 to 39-41%. Using the new synthetic scheme, four kinds of tetracations were synthesized from the combination of two cationic units (imidazolium and pyrrolidinium) and two counteranions [bis(fluorosulfonyl)imide (FSI) and bis(trifluoromethanesulfonyl)imide (TFSI)]. Basic physical properties including glass transition temperature, thermal decomposition temperature, density, viscosity, and ionic conductivity were determined. The counterion exchange from TFSI to FSI resulted in lower glass transition temperature and higher ionic conductivity. Tetrapyrrolidinium exhibited higher viscosity and lower ionic conductivity than tetraimidazolium. The counterion exchange from TFSI to FSI resulted in lower viscosity in the case of tetraimidazolium, while the opposite result was obtained in the case of tetrapyrrolidinium. Tetracations composed of ethyl imidazolium units, diethylene glycol spacers, and FSI counterions exhibited the highest ionic conductivity of 3.5 × 10^-4 S cm^-1 at 25 °C under anhydrous conditions. This is the best ionic conductivity in the tetracations ever reported.

Expanding the Chemical Space of Benzimidazole Dicationic Ionic Liquids

Benzimidazole dicationic ionic liquids (BDILs) have not yet been widely explored in spite of their potential. Therefore, two structurally related families of BDILs, paired with either bromide or bistriflimide anions and bearing alkyl spacers ranging from C3 to C6, have been prepared. Their thermal properties have been studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), while their electrical properties have been assessed by cyclic voltammetry (CV). TG analysis confirmed the higher stability of the bistriflimide BDILs over the bromide BDILs, with minor variation within the two families. Conversely, DSC and CV allowed for ascertaining the role played by the spacer length. In particular, the thermal behavior changed dramatically among the members of the bistriflimide family, and all three possible thermal behavior types of ILs were observed. Furthermore, cyclic voltammetry showed different electrochemical window (C3(C1BenzIm)2/2Tf2N < C4(C1BenzIm)2/2Tf2N, C5(C1BenzIm)2/2Tf2N < C6(C1BenzIm)2/2Tf2N) as well as a reduction peak potential, shape, and intensity as a function of the spacer length. The results obtained highlight the benefit of accessing a more structurally diverse pool of compounds offered by dicationic ILs when compared to the parent monocationic ILs. In particular, gains are to be found in the ease of fine-tuning their properties, which translates in facilitating further investigations toward BDILs as designer solvents and catalysts.

Synthesis, Characterization, and Computational Chemical Study of Aliphatic Tricationic Surfactants as Corrosion Inhibitors for Metallic Equipment in Oil Fields

Aliphatic tricationic surfactants were prepared by the esterification reaction, followed by a quaternization reaction to protect oil well facilities from corrosion problems. Microelemental analysis and Fourier transform infrared and ¹H NMR spectroscopic techniques were performed to explore the obtained motifs. The performance of these amphiphiles as inhibitors for metallic S90 steel corrosion in formation water was investigated through electrochemical tests (potentiodynamic polarization and electrochemical impedance spectroscopy). The results revealed significant inhibition effectiveness improvement with increasing concentrations of these amphiphiles. Its maximum inhibition efficiency reaches 93.07% at 250 ppm for the compound (AED). Potentiodynamic polarization graphs demonstrated that tricationic amphiphiles behave as mixed-type inhibitors. In addition, the adsorption of the tricationic surfactant at the S90 steel surface followed Langmuir isotherm. Atomic force microscopy revealed that a protective layer formed at the surface of S90 steel caused the inhibition of corrosion. During the inhibition procedure of S90 steel corrosion, theoretical research has been performed to validate electrochemical experiments and to clearly demonstrate the mechanism of these amphiphiles. Finally, quantum chemical calculations were calculated to achieve the justification for the obtained empirical results.

Metal-Free Synthesis of Benzimidazoles via Oxidative Cyclization of d-Glucose with o-Phenylenediamines in Water

d-Glucose has been identified as an efficient C1 synthon in the synthesis of benzimidazoles from o-phenylenediamines via an oxidative cyclization strategy. Isotopic studies with ¹³C₆-d-glucose and D₂O unambiguously confirmed the source of methine. The notable features of this method include the following: broad functional group tolerance, a biorenewable methine source, excellent reaction yields, a short reaction time, water as an environmentally benign solvent, and the synthesis of vitamin B₁₂ component on the gram scale.

Ionic magnetic core–shell nanoparticles for DNA extraction

The fabrication ionic magnetic core-shell nanoparticles were simple synthesize with a super-ferromagnetic and small particle size properties, which enabled sufficient DNA particle loading with easy isolation based on an external magnetic field.

Environmental Impact of Ionic Liquids: Recent Advances in (Eco)toxicology and (Bio)degradability

This Review aims to integrate the most recent and pertinent data available on the (bio)degradability and toxicity of ionic liquids for global and critical analysis and on the conscious use of these compounds on a large scale thereafter. The integrated data will enable focus on the recognition of toxicophores and on the way the community has been dealing with them, with the aim to obtain greener and safer ionic liquids. Also, an update of the most recent biotic and abiotic methods developed to overcome some of these challenging issues will be presented. The review structure aims to present a potential sequence of events that can occur upon discharging ionic liquids into the environment and the potential long-term consequences.

Sustainable oleic and stearic acid based biodegradable surfactants

Renewable ester functionalized fatty acid based imidazolium surfactant.

Ionic Liquid Crystals: Versatile Materials

This Review covers the recent developments (2005-2015) in the design, synthesis, characterization, and application of thermotropic ionic liquid crystals. It was designed to give a comprehensive overview of the "state-of-the-art" in the field. The discussion is focused on low molar mass and dendrimeric thermotropic ionic mesogens, as well as selected metal-containing compounds (metallomesogens), but some references to polymeric and/or lyotropic ionic liquid crystals and particularly to ionic liquids will also be provided. Although zwitterionic and mesoionic mesogens are also treated to some extent, emphasis will be directed toward liquid-crystalline materials consisting of organic cations and organic/inorganic anions that are not covalently bound but interact via electrostatic and other noncovalent interactions.

Biodegradation of ionic liquids – a critical review

The importance of biodegradation data as part of the design of safer chemicals is presented using ionic liquids (ILs) as a model study.

Bis-imidazolium and benzimidazolium based gemini-type ionic liquids structure: synthesis and antibacterial evaluation

The incorporated benzenesulfonamide moiety and the active side substituents in di-imidazolium and benzimidazolium cations enhanced both antibacterial activity and miscibility for the synthesized gemini type ILs.