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Ionic liquids (ILs) have emerged as a new class of materials, displaying a unique capability to self-assemble into micelles, liposomes, liquid crystals, and microemulsions. Despite evident interest, advancements in the controlled formation of amphiphilic ILs remain in the early stages. Taking inspiration from nature, we introduced the concept of lipid-like (or lipid-inspired) ILs more than a decade ago, aiming to create very low-melting, highly lipophilic ILs that are potentially bio-innocuous – a combination of attributes that is frequently antithetical but highly desirable from several application-specific standpoints. Lipid-like ILs are a subclass of functional organic liquid salts that include a range of lipidic side chains such as saturated, unsaturated, linear, branched, and thioether while retaining melting points below room temperature. It was observed in several homologous series of [Cnmim] ILs that elongation of N-appended alkyl chains to greater than seven carbons leads to a substantial increase in melting point (Tm) – which is the most characteristic feature of ILs. Accordingly, it is challenging to develop ILs with low Tm values while preserving their hydrophobicity and self-organizing properties. We found that two alternative Tm depressive approaches are useful. One of these is the replacement of the double bonds with thioether moieties in the alkyl chains, as detailed in several published papers detailing the chemistry of these ILs. Employing thiol–ene and thiol–yne click reactions is a facile, robust, and orthogonal method to overcome the challenges associated with the synthesis of alkyl thioether-functionalized ILs. The second approach involves replacing the double bonds with the cisoid cyclopropyl motif, mimicking the strategy used by certain organisms to modulate cell membrane fluidity. This discovery has the potential to greatly impact the utilization of lipid-like ILs in various applications, including gene delivery, lubricants, heat transfer fluids, and haloalkane separations, among others. This feature article presents a concise, historical overview, highlighting key findings from our work while offering speculation about the future trajectory of this de novo class of soft organic-ion materials. [ABSTRACT FROM AUTHOR]

The serendipitous discovery of an unorthodox ionic cocrystallization system using 2-mercaptothiazolium-based ionic liquids as a crystallization milieu paves the way for the first report of crystal structures of long-chain 1-bromoalkanes. We used single crystal X-ray diffraction to determine the structures of 1-bromo-hexadecane and 1-octadecane with the aid of ionic liquids with alkyl side chains of equivalent length to the bromoalkane at room temperature. Long alkyl chains in combination with σ-hole interactions from strategically placed sulfur motifs synergistically function to crystallize the 1-bromoalkanes. [ABSTRACT FROM AUTHOR]

In this work, we investigated the effects of a single covalent link between hydrogen bond donor species on the behavior of deep eutectic solvents (DESs) and shed light on the resulting interactions at molecular scale that influence the overall physical nature of the DES system. We have compared sugar-based DES mixtures, 1:2 choline chloride/glucose [DES(g)] and 1:1 choline chloride/trehalose [DES(t)]. Trehalose is a disaccharide composed of two glucose units that are connected by an α-1,4-glycosidic bond, thus making it an ideal candidate for comparison with glucose containing DES(g). The differential scanning calorimetric analysis of these chemically close DES systems revealed significant difference in their phase transition behavior. The DES(g) exhibited a glass transition temperature of −58 °C and behaved like a fluid at higher temperatures, whereas DES(t) exhibited marginal phase change behavior at −11 °C and no change in the phase behavior at higher temperatures. The simulations revealed that the presence of the glycosidic bond between sugar units in DES(t) hindered free movement of sugar units in trehalose, thus reducing the number of interactions with choline chloride compared to free glucose molecules in DES(g). This was further confirmed using quantum theory of atoms in molecule analysis that involved determination of bond critical points (BCPs) using Laplacian of electron density. The analysis revealed a significantly higher number of BCPs between choline chloride and sugar in DES(g) compared to DES(t). The DES(g) exhibited a higher amount of charge transfer between the choline cation and sugar, and better interaction energy and enthalpy of formation compared to DES(t). This is a result of the ability of free glucose molecules to completely surround choline chloride in DES(g) and form a higher number of interactions. The entropy of formation for DES(t) was slightly higher than that for DES(g), which is a result of fewer interactions between trehalose and choline chloride. In summary, the presence of the glycosidic bond between the sugar units in trehalose limited their movement, thus resulting in fewer interactions with choline chloride. This limited movement in turn diminishes the ability of the hydrogen bond donor to disrupt the molecular packing within the lattice structure of the hydrogen bond acceptor (and vice versa), a crucial factor that lowers the melting point of DES mixtures. This inability to move due to the presence of the glycosidic bond in trehalose significantly influences the physical state of the DES(t) system, making it behave like a semi-solid material, whereas DES(g) behaves like a liquid material at room temperature. [ABSTRACT FROM AUTHOR]

A heteroaryl sulfonyl(VI) fluoride, 4‐chloro‐7‐fluorosulfonyl‐2,1,3‐benzoxadiazole, was synthesized from its chloride counterpart (4‐chloro‐7‐chlorosulfonyl‐2,1,3‐benzoxadiazole) and the X‐ray structure analysis of these compounds and the interactions in the solid‐state were thoroughly examined. Hirshfeld surface analysis is used to provide a thorough and complete picture of the changes arising from the different halides in the functional groups. Surface analysis reveals that the fluoride does not participate in any hydrogen interactions as opposed to the chloride. However, the fluorine atom is observed to form close interactions with several π bonds. For both moieties, however, the sulfonyl oxygens show comparable interactions with respect to both magnitude and interatomic distances. The Hirshfeld surface analysis is coupled with computational studies to help elucidate the observed interactions that are found from the distinct nitrogen, chlorine, and oxygen atoms present in the molecules, providing new physical insights to the correlation between their structures and properties [ABSTRACT FROM AUTHOR]

The continued success of ionic liquids in applications ranging from energy to medicine poses the challenge to rapidly find new functional ionic liquids with desirable properties while developing practical, scalable syntheses. As a SuFExable functionality, the sulfonyl fluoride has become widely adopted throughout the field of chemical biology due, in part, to its unique stability–reactivity pattern, highlighting the underappreciated potential of the SVI–F motif in materials chemistry. For the first time, we herein report the development of a set of sulfonyl fluoride-functionalized ionic liquids with considerable structural diversity via an efficient, modular, and orthogonal fluorosulfonylethylation procedure. The resulting SO2F-functionalized ionic milieu has properties consistent with its classification as ionic liquids. We employed a combination of molecular design, synthesis, computational modeling, and X-ray crystallographic studies to gain in-depth understanding of their structure–property correlations. The diversification of the SO2F-bearing salts is extended to include active pharmaceutical precursors, allowing for access to functional materials with a priori low toxicity. [ABSTRACT FROM AUTHOR]

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We present an efficient Ullmann-type synthesis methodology enabling the preparation of imidazolium compounds with an extended aromatic core in three steps. This procedure begins with a microwave-assisted, heterogeneously catalysed cross-coupling reaction in the presence of Cu(ii)-doped NaY zeolite to obtain imidazole-aromatic derivatives directly in good yield. The innovation is that this reaction does not require solvent, ligand or an inert atmosphere. Subsequently, these derivatives have been alkylated with bromoalkanes and the bromide of the imidazolium products exchanged for [BF4]− or [PF6]− anions. We have studied the influence of the methyl group (inductive effect) on the aromatic unit during the coupling reaction as well as its impact on different arrangements in the crystalline state. We have been able to extend this synthesis to ionic liquid crystal compounds which display lamellar self-organization (smectic A). The mesomorphic behavior and phase transition temperatures were investigated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS). [ABSTRACT FROM AUTHOR]

Since the introduction of click chemistry by K. B. Sharpless in 2001, its exploration and exploitation has occurred in countless fields of materials sciences in both academic and industrial spheres. Click chemistry is defined as an efficient, robust, and orthogonal synthetic platform for the facile formation of new carbon–heteroatom bonds, using readily available starting materials. Premier examples of click reactions are copper(i)-catalyzed azide–alkyne Huisgen cycloaddition (CuAAC) and the thiol–X (X = ene and yne) coupling reactions to form C–N and C–S bonds, respectively. The emphasis of this review is centered on the rapidly expanding area of click chemistry-mediated synthesis of functional ionic liquids via CuAAC, thiol–X and oxime formation, and selected examples of nucleophilic ring-opening reactions, while offering some thoughts on emerging challenges, opportunities and ultimately the evolution of this field. Click chemistry offers tremendous opportunities, and introduces intriguing perspectives for efficient and robust generation of tailored task-specific ionic liquids – an important class of soft materials. [ABSTRACT FROM AUTHOR]

This study introduces a novel class of imidazolium- and ammonium-based ionic liquids possessing two C12 and C14 tails and thioether linkers designed for lipoplex-mediated DNA delivery. Imidazolium-based ionic liquids displayed efficient gene delivery properties with low toxicity. Thiol–yne click chemistry was employed for the facile and robust synthesis of these thioether-based cationic lipioids with enhanced lipophilicity and low fluidity. [ABSTRACT FROM AUTHOR]

A series of ionic liquids containing 3- and 4-picolinium cations appended to thioether side chain moieties was constructed via the thiol–ene “click” reaction. Their structure–property relationships were comprehensively investigated by studying the temperature transition region (melting points and glass transition temperatures) and heat capacity and the experimental results were fully supported by theoretical studies. The synthesized ionic liquids are melted below 20.2 °C. Also, the impact of varying chain length, type of cations (picolinium vs. imidazolium) and the position of methyl group on the ring on their thermal and thermophysical properties were explored. According to the collected data, the glass transition temperature values of the picolinium-based ionic liquids with odd-number chains is lower than the even-number ones, which shows that the even-number moieties have more organized structures. And the miscibility of selected ionic liquids in water (polar) and heptane (nonpolar) solvents were quantified. [ABSTRACT FROM AUTHOR]

We demonstrate herein a facile synthesis of a series of highly-ordered low-melting protic ionic liquids with linear C16–C20 side chains identical to natural fatty acids, which were produced by the S-alkylation of the 2-mercapto-1-methylimidazole (methimazole) ring. There is considerable structural latitude possible when designing highly lipophilic protic ionic liquids that exhibit low Tm values due to the cumulative disruptive effects of thioether and unsaturation on their packing efficiency. Their bulk thermophysical properties, hydrophobicity and cytotoxicity were also determined. [ABSTRACT FROM AUTHOR]

We describe the facile, robust and orthogonal fabrication of a structurally comprehensive library of hydrophobic trimethoxysilyl-functionalized ionic liquids with C7–C15 thioether spacer, using thiol–ene “click” chemistry. The synthesized ionic liquids displayed very low glass transition temperatures, high thermal stability and were hydrophobic in character. And the ability to serve as surface coating agents was tested by immobilizing them on the surface of iron oxide supermagnetic nanoparticles and the organic loadings were quantified. [ABSTRACT FROM AUTHOR]

This study focuses on the synthesis of a class of novel biologically-inspired ionic liquids coupled with a phosphonate group containing short to long side chains (C3–C11) via the Pudovic reaction. The ionic liquids exhibited very low glass transition temperatures and were hydrophobic in character. This method has the attributes of “click” chemistry with outstanding efficiency, simplicity, yields and regioselectivity. The results of their calcium(ii) ligating capability are also presented. [ABSTRACT FROM AUTHOR]

The synthesis of a series of new lipid-inspired ionic liquids through thiol-ene 'click' reaction with a single-step process. This synthesis offers considerable promise as an efficient and orthogonal method to construct structurally diverse imidazolium-type ionic liquids with linear and branched cationic tails, as well as versatility in the placement of the sulfur heteroatom. Profound solvent effect in this ene reaction regioselectivity has been observed. [ABSTRACT FROM AUTHOR]

An efficient method for the synthesis of a series of 2,3-disubstituted-2,3-dihydroquinazolin-4( 1H)-ones is described via one-pot condensation reaction of isatoic anhydride, aryl aldehydes, and primary amines using a Brønsted acidic ionic liquid, [Hmim][NO3], as a catalyst and medium. The present protocol enjoys convenient reaction and simple work-up, greenness, short reaction times, and reusable catalyst as well as mild reaction conditions. J. Heterocyclic Chem., (2011). [ABSTRACT FROM AUTHOR]

Contamination of medical devices with bacteria such as Meticillin resistant Staphylococcus aureus(MRSA) is of great clinical concern. Poly(vinyl chloride) is widely used in the production of medical devices, such as catheters. The flexibility of catheter tubing is derived from the addition of plasticisers. Here, we report the design of two dual functional ionic liquids, 1-ethylpyridinium docusate and tributyl(2-hydroxyethyl)phosphonium docusate, which uniquely provide a plasticising effect, and exhibit antimicrobial and antibiofilm-forming activity to a range of antibiotic resistant bacteria. The plasticisation of poly(vinyl chloride) was tailored as a function of ionic liquid concentration. The effective antimicrobial behaviour of both ionic liquids originates from the chemical structure of the anion or cation and is not limited to the length of the alkyl chain on the anion/cation. The design approach adopted will be useful in developing ionic liquids as multi-functional additives for polymers. [ABSTRACT FROM AUTHOR]

A series of 2,4-disubstituted quinolines were easily prepared through a one-pot reaction of structurally diverse 2-aminoaryl ketones with various arylacetylenes in the presence of K5CoW12O40˙3H2O as a reusable and environmentally benign catalyst under microwave irradiation and solvent-free conditions. [ABSTRACT FROM AUTHOR]