Cation-dipole Interactions Research Articles

Theoretical simulation of OH− transport in poly(arylene indole piperidinium) anion exchange membranes: Effect of side-chain chemical structure

The introduction of long side chains into anion exchange membranes (AEMs) is a common strategy for improving OH− transport. However, the effect of different chemical structures of side-chain on OH− transport in poly(arylene indole piperidinium) AEMs remains unclear. This study investigates the effects of four distinct side-chain chemical structures in poly(arylene indole piperidinium) AEMs (specifically, all-carbon side chains (a-PITPC10), side chains with amino groups (a-PITPC7N3), side chains with ethoxy groups (a-PITPC7O3), and side chains with fluoro groups (a-PITPC10F21)) on OH− transport rates and mechanisms using molecular dynamics (MD) simulation methods. The simulation results show that the trend of OH− transport rate at the same hydration number is a-PITPC7N3 < a-PITPC10F21 < a-PITPC10 < a-PITPC7O3. The flexible side chains containing ether oxygen groups have a stronger ability to move, hence the segments have a higher degree of freedom of movement, which is beneficial to the construction of a favorable micro-morphology. At the same time, the cation-dipole interaction between the main chain cation and the ether oxygen group in the side chain of a-PITPC7O3 promotes the aggregation of nearby cationic groups, enlarging the overlapping area of the surrounding hydration shells, thereby facilitating the transport of OH−. Compared to a-PITPC10, in a-PITPC7N3, the strong hydrophilicity of the side chains causes water molecules to tend to disperse, and the bottleneck volume fraction occupied by ion transport channels is the largest, hindering OH− transport. Moreover, in a-PITPC10F21, the strongly hydrophobic side chains cause water molecules to aggregate excessively, forming wide ion transport channels, but their continuity is poor, which is not conducive to OH− transport. The flexible side chains in a-PITPC7O3 facilitate the uniform dispersion of water molecules in the system, forming continuous ion transport channels, which is conducive to improving OH− transport performance. Therefore, the poly(arylene indole piperidinium) AEM with ether oxygen groups (a-PITPC7O3) outperforms other side-chain structured AEMs (a-PITPC10, a-PITPC7N3, and a-PITPC10F21) in improving OH− transport.

Non-covalently crosslinked networks MXene-doped poly(eutectic) conductive elastomers with antimicrobial, self-healing, tunable mechanical properties, and wide temperature durability

Poly(eutectic) elastomers, as an emerging category of flexible electronic materials, have garnered growing interest for their cost-effectiveness, non-volatility, and biocompatibility. Nonetheless, they encounter challenges including limited functionalities, sensitivity, durability, and mechanical properties. This study involved synthesizing various MXene-doped poly(eutectic) elastomers using robust acrylamide and soft acrylic acid as organic monomers, minor MXene nanosheets as inorganic fillers and physical crosslinkers, and a rapid in-situ photopolymerization method within 2 min. Owing to the synergistic effect of thermodynamic self-assembly, high-density hydrogen bonding, and cation-dipole interactions in the matrix networks, the resulting non-covalently crosslinked elastomers exhibited remarkable mechanical strength (up to ∼ 16.2 MPa) and impressive tensile properties (nearly 700 %), along with rapid electrical self-healing (within 0.046 s) and the ability to withstand loads up to 2500 times their weight following self-healing without fracturing. Notably, these elastomers also demonstrated excellent microstrain (1 %–10 %) sensitivity with a gauge factor of 2.02, wide temperature tolerance (−20 °C ∼ 60 °C), outstanding harsh temperature durability (−20 °C) exceeding 22,000 cycles, and antibacterial properties. Furthermore, these elastomers-assembled strain sensors displayed real-time and rapid response in human motion detection and wireless signal transmission, presenting a promising approach for designing functionally integrated elastomeric materials.

Elucidating the role of polar functional groups in fluorinated polymer artificial interphase for stable lithium anodes

The properties of solid electrolyte interphase (SEI) are pivotal for stable lithium (Li) metal anodes. However, the process of formation and ion transport behavior of lithium fluoride (LiF) through the polar groups of organic fluorinated artificial SEI has not been clearly elucidated. Herein we demonstrate that the key role of polar functional groups in fluorinated polymer artificial SEI (FPASEI) is elucidated by using 2,2,2-trifluoroethylacrylate (TFEA) through radical polymerization. Density functional theory and ab initio molecular dynamics calculations demonstrate that the abundant CO polar groups in TFEA contribute a large number of electrons, thereby facilitating the degradation kinetics of CF bond cleavage in lithium bis(trifluoromethanesulfonyl)imide salt to yield LiF. Moreover, the presence of CF, COC, and CO groups in TFEA facilitate the migration of Li+ towards interchain regions through cation-dipole interaction, leading to dendrite-free Li deposition. The implementation of FPASEI in a Li||Li cell results in 500 h of Li plating/stripping cycling at 1 mA cm−2 and retains a capacity retention rate of 80 % after 265 cycles in Li||LiNi0.8Co0.1Mn0.1O2 cell. This study not only emphasizes the critical role of polar groups in artificial SEI but also presents a promising strategy for achieving stable Li metal batteries.

Fluorinated Poly(thiophene-based aryl piperidinium) Anion-Exchange Membranes Containing Dual Cation–Dipole Interactions for Alkaline Fuel Cells

Fluorinated Poly(thiophene-based aryl piperidinium) Anion-Exchange Membranes Containing Dual Cation–Dipole Interactions for Alkaline Fuel Cells

Regulating Access to Active Sites via Hydrogen Bonding and Cation-Dipole Interactions: A Dual Cofactor Approach to Switchable Catalysis.

Hydrogen bonding networks are ubiquitous in biological systems and play a key role in controlling the conformational dynamics and allosteric interactions of enzymes. Yet in small organometallic catalysts, hydrogen bonding rarely controls ligand binding to the metal center. In this work, a hydrogen bonding network within a well-defined organometallic catalyst works in concert with cation-dipole interactions to gate substrate access to the active site. An ammine ligand acts as one cofactor, templating a hydrogen bonding network within a pendent crown ether and preventing the binding of strong donor ligands, such as nitriles, to the nickel center. Sodium ions are the second cofactor, disrupting hydrogen bonding to enable switchable ligand substitution reactions. Thermodynamic analyses provide insight into the energetic requirements of the different supramolecular interactions that enable substrate gating. The dual cofactor approach enables switchable catalytic hydroamination of crotononitrile. Systematic comparisons of catalysts with varying structural features provide support for the critical role of the dual cofactors in achieving on/off catalysis with substrates containing strongly donating functional groups that might otherwise interfere with switchable catalysts.

Anisotropic ion-conductive supramolecular columnar liquid crystals composed of a benzonitrile derivative and ionic liquids

Self-organized liquid-crystalline (LC) electrolytes, which feature externally controllable ion channels, are at the forefront of advanced materials for developing next generation batteries and actuators. In this study, we present a novel family of supramolecular columnar liquid crystals that exhibit anisotropic ion-conducting properties. These liquid crystals are formed by self-assembly of a taper-shaped benzonitrile derivative with an amide moiety and ionic liquids (1-ethyl-3-methylimidazolium bromide and 1-butyl-3-methylimidazolium bromide). The cooperative interactions between the nitrile dipole-ion interaction and the bromide anion–amide NH hydrogen bond effectively confine ionic liquids to the center of columns, forming one-dimensional channels. By applying a shearing force, we achieved a uniform horizontal orientation of the supramolecular columns between comb-shaped gold electrodes deposited on a glass substrate. The columnar LC complexes that contained larger cations exhibited higher ionic conductivities compared to those with smaller cations. This can be attributed to the effective ion dissociation resulting from weak Coulombic interactions caused by the larger size of the ionic liquid, as well as the attractive cation-dipole interaction. The present study not only contributes to the understanding of the interplay of noncovalent forces but also offers insights for the design of functional supramolecular materials for future ionic devices.

Production of high-energy 6-Ah-level Li | |LiNi0.83Co0.11Mn0.06O2 multi-layer pouch cells via negative electrode protective layer coating strategy

Stable lithium metal negative electrodes are desirable to produce high-energy batteries. However, when practical testing conditions are applied, lithium metal is unstable during battery cycling. Here, we propose poly(2-hydroxyethyl acrylate-co-sodium benzenesulfonate) (PHS) as negative electrode protective layer. The PHS contains soft poly (2-hydroxyethyl acrylate) and poly(sodium p-styrene sulfonate), which improve electrode flexibility, connection with the Cu current collector and transport of Li ions. Transmission electron cryomicroscopy measurements reveal that PHS induces the formation of a solid electrolyte interphase with a fluorinated rigid and crystalline internal structure. Furthermore, theoretical calculations suggest that the -SO3- group of poly(sodium p-styrene sulfonate) promotes Li-ion motion towards interchain migration through cation-dipole interaction, thus, enabling uniform Li-ion diffusion. Electrochemical measurements of Li | |PHS-coated-Cu coin cells demonstrate an average Coulombic efficiency of 99.46% at 1 mA/cm2, 6 mAh/cm2 and 25 °C. Moreover, when the PHS-coated Li metal negative electrode is paired with a high-areal-capacity LiNi0.83Co0.11Mn0.06O2-based positive electrode in multi-layer pouch cell configuration, the battery delivers an initial capacity of 6.86 Ah (corresponding to a specific energy of 489.7 Wh/kg) and, a 91.1% discharge capacity retention after 150 cycles at 2.5 mA/cm2, 25 °C and 172 kPa.

Highly conductive, anti-freezing, and adhesive hydrogels containing pores constructed by cation–dipole interactions

The low ionic conductivity of most hydrogels limits their application in various fields. Boosting ion conductivity in anion exchange membranes (AEMs) using dipole-ion interactions (electrostatic attraction between anions and neutral dipole molecules) with exceptional interaction energies of 20 to 200 kJ mol−1 is the best way to create ion channels in anion exchange membranes (AEMs). In this study, intending to increase the ionic conductivity of hydrogels, the antifreeze crosslinked PVA/PVP hydrogels (5, 10, and 15% Cr-PVA) were prepared using 1,10-dibromodecane (DBD) to crosslink PVA and PVP via SN2 reaction to create multiple pores morphology in the hydrogels by cation-dipole interactions. Moreover, the prepared hydrogels contain cationic groups facilitating ion transport through the hopping mechanism. There was a significant difference in ionic conductivity between the 10% Cr-PVA hydrogel (2.63 S m−1) and the PVA hydrogel (0.76 S m−1) at room temperature due to the multiple pores created with cation-dipole interaction. Despite excellent mechanical properties, 10% Cr-PVA at −20 °C (1.25 S m−1) has a higher ionic conductivity than most antifreeze conductive hydrogels. Eventually, the 10% Cr-PVA hydrogel with gauge factor 1.97 demonstrated the desired sensitive response performance for sensor applications.

Tunable and Switchable Catalysis Enabled by Cation-Controlled Gating with Crown Ether Ligands

ConspectusCatalysis has become an essential tool in science and technology, impacting the discovery of pharmaceuticals, the manufacture of commodity chemicals and plastics, the production of fuels, and much more. In most cases, a particular catalyst is optimized to mediate a particular reaction, continually producing a desired product at a given rate. There is enormous opportunity in developing catalysts that are dynamic, capable of responding to a change in the environment to alter structure and function. Controlled catalysis, in which the activity or selectivity of a catalytic reaction can be adjusted through an external stimulus, offers opportunities for innovation in catalysis. Catalyst discovery could be simplified if a single thoughtfully designed complex could work synergistically with additives to optimize performance rather than trying a multitude of different metal/ligand combinations. Temporal control could be gained to facilitate the execution of multiple reactions in the same flask, for example, by activating one catalyst and deactivating another to avoid incompatibilities. Selectivity switching could enable copolymer synthesis with well-defined chemical and material properties. These applications might sound futuristic for synthetic catalysts, but in nature, such a degree of controlled catalysis is commonplace. For example, allosteric interactions and/or feedback loops modulate enzymatic activity to enable complex small-molecule synthesis and sequence-defined polymerization reactions in complex mixtures containing many catalytic sites. In many cases, regulation is achieved by "gating" substrate access to the active site. Fundamental advances in catalyst design are needed to better understand the factors that enable controlled catalysis in the arena of synthetic chemistry, particularly in achieving substrate gating outside of macromolecular environments. In this Account, the development of design principles for achieving cation-controlled catalysis is described. The guiding hypothesis was that gating substrate access to a catalyst site could be achieved by controlling the dynamics of a hemilabile ligand through secondary Lewis acid/base and/or cation-dipole interactions. To enforce such interactions, catalysts sitting at the interface of organometallic catalysis and supramolecular chemistry were designed. A macrocyclic crown ether was incorporated into a robust organometallic pincer ligand, and these "pincer-crown ether" ligands have been explored in catalysis. Complementary studies of controlled catalysis and detailed mechanistic analysis guided the development of iridium, nickel, and palladium pincer-crown ether catalysts capable of substrate gating. Toggling the gate between open and closed states leads to switchable catalysis, where cation addition/removal changes the turnover frequency or the product selectivity. Varying the degree of gating leads to tunable catalysis, where the activity can be tuned based on the identity and amount of salt added. Research has focused on reactions of alkenes, particularly isomerization reactions, which has in turn led to design principles for cation-controlled catalysts.

Highly Conducting Poly(arylene-imidazolium) Anion Exchange Membranes Containing Thin-Span Channels Constructed by Cation–Dipole Interaction

The membrane-based alkaline electrolyzer and fuel cell system has a significant drawback because it uses a concentrated, corrosive alkaline electrolyte. The anion exchange membranes (AEMs) also have lower conductivity than proton exchange membranes (PEMs) because OH– ions have a lower penetration coefficient. In this study, intending to prepare AEMs with high ionic conductivity in low concentrations of alkaline solution, two imidazolium diol monomers have been synthesized as unique candidates for the synthesis of stable anion exchange polymers. Then a strategy for designing AEMs with ion-conducting channels using a strong cation-dipole interaction between imidazolium cations and polar poly(vinylpyrrolidone) (PVP) (PAIm1/PVP blend membrane and Cross-PAIm1-PVP membrane) was reported. At 25 °C, the PAIm1/PVP blend and Cross-PAIm1-PVP membrane have ionic conductivities of 77.1, 104.9 mS cm–1 in water (Cl– form), and 315, 356.1 mS cm–1 in KOH 0.2 M, respectively. Also, a semicrystalline poly(arylene-imidazolium)2 (PAIm2) was synthesized and blended with PVP to increase the ions’ orientation for boosted ion conductivity. The ionic conductivity of the PAIm2/PVP blend membrane is 25.9 mS cm–1 in water (Cl– form) and 86.1 mS cm–1 in KOH 0.2 M at 25 °C. In addition, the prepared membranes in direct ethanol fuel cells (DEFCs) show preferable behavior in single-cell performance, with a peak power density (Pmax) of 17.7, 11.1, and 9.1 mW cm–2 at 30 °C for PAIm1/PVP, PAIm2/PVP, and Cross-PAIm1-PVP membranes, respectively. The results demonstrate that the prepared AEMs can use in electrolyzers and fuel cells.

Cross-Linked Anion-Exchange Membranes with Dipole-Containing Cross-Linkers Based on Poly(terphenyl isatin piperidinium) Copolymers.

To balance the ionic conductivity and dimensional stability of anion-exchange membranes (AEMs), several cross-linked ether-free poly(terphenyl isatin piperidinium) copolymers were synthesized using 1,2-bis(2-aminoethoxy)ethane as a cross-linker. By introducing an alkyl diamine-based hydrophobic cross-linker as a control, the effects of the dipolar-molecule-containing cross-linker on the comprehensive performance of the membranes were investigated. Cation-dipole interactions between the cations and the hydrophilic ethylene oxide cross-linker enhance the self-assembly capability of the cationic groups. The introduction of the rotatable ethylene oxide cross-linker facilitates the flexibility of the cross-linked networks, thereby promoting hydrophilic/hydrophobic phase separation and inhibiting excessive swelling of the corresponding AEMs simultaneously. The resulting PTPBHIN-O19 membrane showed a high hydroxide conductivity (151.69 mS cm-1) and low swelling ratio (10.53%) at 80 °C. Furthermore, owing to the cross-linked structure and ether-free polymer backbone with high alkali resistance, the membranes treated in 3 M NaOH at 80 °C for 1600 h maintained ≥85% of their hydroxide conductivity, indicating excellent alkaline stability. A H2/O2 fuel cell based on the PTPBHIN-O19 AEM exhibited a maximum power density of 398 mW cm-2 at 515 mA cm-2.

Guanine-Based G-Quadruplexes Templated by Various Cations toward Potential Use as Single-Ion Conductors.

Inspired by the atomic-sized, shape-regulated features of G-quadruplexes comprising guanine motifs with a monovalent metal cation, the G-quadruplex-forming ability, and properties of a guanine-based π-conjugated Y2 molecule containing bithiophene and peripheral dodecyl chain units in the presence of various cation salts (Li+ , Na+ , K+ , and Mg2+ ) were exploited. A series of structural characterization revealed that Y2 yielded desirable G-quadruplexes with all the tested cations as a consequence of the combination of a hydrogen-bonded cyclic G-quartet, π-stacking, and cation-dipole interactions. The radius and nature of the coordinating cations crucially affected the structural characteristics of G-quadruplexes, leading to variations in the ion migration ability inside the cavity of the G-quadruplex (Li+ >Na+ >K+ >Mg2+ ), as characterized through theoretical and experimental investigations. These results not only improve the understanding of G-quadruplex self-assemblies based on guanine but also provide an impetus for their diverse potential applications, especially in the field of Li batteries.

Anion exchange membranes with fast ion transport channels driven by cation-dipole interactions for alkaline fuel cells

Polyethylene glycol (PEG)-grafted imidazolium-containing flexible-side-chain type anion exchange membrane (AEM) has been designed and fabricated for efficient anion exchange membrane fuel cells (AEMFCs). The cation-dipole interactions between electronegative alkoxy and imidazolium drive the spontaneous self-assembly of the cationic side chains, thus boosting the formation of continuous ion-conducting channels with enhanced OH− conduction kinetic. The PEG's H-bonding with H2O molecules improves the hydrophilicity of the AEMs, thereby reducing the dependence of OH− transport on relative humidity (RH). Meanwhile, the alkaline stability of PEG-grafted AEMs has been improved since the electrostatic interactions reduce the electrophilicity of imidazolium for potential hydroxide attack. Compared with OBImPPO26-PEG0, the designed OBImPPO26-PEG0.5 (with 0.5% PEG grafts) membrane exhibits higher OH− conductivity (93.8 mS cm−1vs. 80.9 mS cm−1, 80 °C) and conductivity remaining (80.4% vs. 51.0%, treated by 2 mol L−1 aqueous NaOH for 216 h at 60 °C). The peak power density of an H2/O2 single-cell employing OBImPPO26-PEG0.5 membrane reaches up to 407 mW cm−2 at 60 °C.

Cation–dipole interaction that creates ordered ion channels in an anion exchange membrane for fastOH−conduction

AbstractPrecise control over polyelectrolyte architecture, engineered for self‐assembly of ion‐conducting channels, is of fundamental and technological importance to many fields, for example, fuel cells and redox flow batteries and electrodialysis. Building on recent advances with the supramolecular chemistry, we introduce inter/intra‐molecular cation–dipole interactions between pendent quaternary ammoniums cations and polar polyethylene glycol grafts in an anion‐exchange membrane (AEM). Such interactions lead to desirable, ordered ion‐conducting pathways when in the membrane form. Comparison of the results of molecular dynamics simulation with1H NMR and nano‐scale microscopy analyses show that the cation–dipole interactions enhance self‐assembly and the formation of interconnected ionic network domains, providing three‐dimensional pathways for both water and ion transport. The resultant AEM exhibits high OH−conductivity (49 mS cm−1at 30°C) and a completive peak power density of 622 mW cm−2at 70°C when tested in a H2/O2single‐cell alkaline membrane fuel cell.

An ultra-low detection limit gold(III) probe based on rhodamine-covalent hydrogel sensor

ABSTRACT A highly sensitive and selective optical chemosensor (Arg-Rhoen) for determination of Au3+ was prepared by covalent immobilization of rhodamine ethylenediamine on agarose gel. Spectrophotometric studies of complex formation, chemical structures and purity of the hydrogel sensor were carried out using TGA, NMR, TEM, and IR. The complexation study results indicated that this probe can selectively detect Au3+ via a metal ion chelation-induced ring-opening reaction, and then caused a remarkable colour change from colourless to pink and a strong fluorescence enhancement. Theoretical DFT calculation results suggested that the hydrogel sensor Arg-Rhoen formed stable complexes with Au3+ through a large number of cation–dipole interactions. Reusability has been established by repeatedly dipping and rinsing the hydrogel in aqueous Au3+ and EDTA in basic solutions. We believe that this approach may provide an easily measurable and inherently sensitive method for Au3+ detection in environmental and biological applications.

Cation−π Interactions Accelerate the Living Cationic Ring-Opening Polymerization of Unsaturated 2-Alkyl-2-oxazolines

Cation–dipole interactions were previously shown to have a rate-enhancing effect on the cationic ring-opening polymerization (CROP) of 2-oxazolines bearing a side-chain ester functionality. In line...

Permeation mechanisms through the selectivity filter and the open helix bundle crossing gate of GIRK2

G protein-gated inwardly rectifying potassium channels (GIRK) are essential for the regulation of cellular excitability, a physiological function that relies critically on the conduction of K+ ions, which is dependent on two molecular mechanisms, namely selectivity and gating. Molecular Dynamics (MD) studies have shown that K+ conduction remains inefficient even with open channel gates, therefore further detailed study on the permeation events is required. In this study, all-atom MD simulations were employed to investigate the permeation mechanism through the GIRK2 selectivity filter (SF) and its open helix bundle crossing (HBC) gate. Our results show that it is the SF rather than the HBC or the G-loop gate that determines the permeation efficiency upon activation of the channel. SF-permeation is accomplished by a water-K+ coupled mechanism and the entry to the S1 coordination site is likely affected by a SF tilt. Moreover, we show that a 4-K+ occupancy in the SF-HBC cavity is required for the permeation through an open HBC, where three K+ ions around E152 help to abolish the unfavorable cation-dipole interactions that function as an energy barrier, while the fourth K+ located near the HBC allows for the inward transport. These findings facilitate further understanding of the dynamic permeation mechanisms through GIRK2 and potentially provide an alternative regulatory approach for the Kir3 family given the overall high evolutionary residue conservation.

Immobilization of unmodified aminoanthraquinone derivatives onto silica gel surface for solid-phase extraction and pre-concentration of Pb(II)

ABSTRACT In this project, silica gel chemically bonded with derivatives of aminoanthraquinone were synthesized and characterized. Adsorbents 1,8-aminoanthraquinone-3-aminopropylsilica (SL1), 2-aminoanthraquinone-3-aminopropylsilica (SL2) and 1-aminoanthraquinone-3-aminopropylsilica (SL3) were produced and tested to adsorb heavy metal solutions including Pb(II) Cu(II) Zn(II) Cd(II) and Co(II). The concentrations of the adsorbed heavy metals solution were calculated by atomic adsorption spectrophotometry employing a batch method. The results showed that speed at 200 rpm for 30 min with pH 9 is the optimum condition for heavy metal adsorption. The result also indicated that adsorbent SL3 is the best adsorbent for Pb(II) at 82.5%, and the relative standard deviation (R.S.D.) was lower than 6%. The method detection limit was 1.1 µg L−1 for Pb2+. In addition, Density Functional Theory (DFT) calculation results suggested that the adsorbent sensor formed stable complexes with Pb(II) through a large number of cation-dipole interactions. The method was also applied with satisfactory results to the pre-concentration of trace Pb(II) in environmental samples.

Solvation Structure of Poly(benzyl methacrylate) in a Solvate Ionic Liquid: Preferential Solvation of Li-Glyme Complex Cation.

We report the solvation structure of a lower critical solution temperature (LCST)-type thermoresponsive polymer in a solvate ionic liquid (SIL, i.e., an ionic liquid comprising solvate ions) to elucidate the predominant interaction for the dissolution of the thermoresponsive polymer in SIL at low temperatures. The solvation structure of poly(benzyl methacrylate) (PBnMA) and a model compound of its monomer in a typical glyme-based SIL, [Li(G4)][TFSA] (G4: tetraglyme; TFSA: bis(trifluoromethanesulfonyl)amide), have been investigated using high-energy X-ray total scattering and all-atom molecular dynamics simulations. In the model compound/SIL system, the intermolecular components extracted from the total G( r)s revealed that the ester moiety of BnMA is preferentially solvated by Li cations through a cation-dipole interaction, which induces slight desolvation of the G4 molecules, and the aromatic ring of BnMA is secondarily solvated by the [Li(G4)] cation complex through a cation-π interaction with maintaining the complex structure. In contrast, TFSA anions are attracted only by the [Li(G4)] cation. These interactions result in the formation of a solvation layer of SILs around the aromatic ring, which plays a key role in the negative entropy and enthalpy of mixing. Meanwhile, in the polymer solution, the coordination number of the Li cation around the ester moiety significantly decreased. This could be ascribed to the steric effect of the bulky side chains, preventing the approach of the [Li(G4)] cation complex to the ester moiety located near the main chain. These solvation structures lead to small absolute values of negative entropy and enthalpy of mixing, which together are key factors to understand the LCST-type phase behavior in the IL system.

GMP-quadruplex-based hydrogels stabilized by lanthanide ions

This work describes the gelation behaviors and properties of a biological molecule, guanosine 5′-monophosphate disodium salt (GMP), in the presence of trivalent lanthanide ions. Hydrogels composed of GMP-quadruplexes were prepared by adjusting pH, through which the protonation of phosphate group was controlled to tune the interactions between lanthanide ions and GMP. Within the pH region of 2–6, the electrostatic interaction between lanthanide ions and phosphate group is hindered and the cation-dipole interaction acts as the main driving force for the formation of G-quadruplexes. All the hydrogels were found consisting of three-dimensional network of the intertwining one-dimensional nanofibers formed by the stacking G-quartets induced by lanthanide ions. A significant fluorescence enhancement of thioflavin T (ThT), a fluorescent molecule, was found to be triggered by the G-quadruplex structures, for which the rotation of chromophoric groups on ThT molecules were prohibited due to the implant into the G-quadruplex structures.