Pyridinium Cations Research Articles

Unveiling the electrophilic aromatic substitution reactions of pyridine derivatives with nitronium ion through molecular electron density theory

The nitration of pyridine Py and pyridine-1-oxide PyO have low activation Gibbs free energies, but in the medium acid, the corresponding pyridinium cation PyH+ is strongly deactivated for the electrophilic aromatic substitution.

Temperature dependence of radiative and non-radiative decay in the luminescence of one-dimensional pyridinium lead halide hybrids.

The photoluminescence properties of organic-inorganic pyridinium lead bromide [(pyH)PbBr3] and iodide [(pyH)PbI3] compounds were investigated as a function of temperature. The inorganic substructure consists of face-sharing chains of PbX6 octahedra. Diffuse reflectance spectra of the compounds show low energy absorption features consistent with charge transfer transitions from the PbX3 chains to the pyridinium cations. Both compounds display extremely weak luminescence at room temperature that becomes strongly enhanced upon cooling to 77 K. Broad, featureless low energy emission (λem > 600 nm) in both compounds have large Stokes shifts [1.1 eV for (pyH)PbBr3 and 0.46 eV for (pyH)PbI3] and are assigned to transitions from self-trapped excitons on the inorganic chains whereas emission at higher energy in (pyH)PbBr3 (λem = 450 nm) is assigned to luminescence from a free exciton state. Analysis of data from temperature-dependent luminescence intensity measurements gives activation energies (Ea) for non-radiative decay of the self-trapped excitons in (pyH)PbBr3 and (pyH)PbI3, (Ea = 0.077 eV and 0.103 eV, respectively) and for the free exciton in (pyH)PbBr3 (Ea = 0.010 eV). Analysis of temperature dependent luminescence lifetime data indicates another non-radiative decay process in (pyH)PbI3 at higher temperatures (Ea = 0.17 eV). A large increase in the luminescence lifetime of (pyH)PbI3 below 80 K is consistent with thermalization between triplet sublevels. Analysis of the luminescence power dependence for (pyH)PbI3 shows superlinear response suggestive of quenching by static traps.

Fluorescent styryl pyridine-N-oxide probes for imaging lipid droplets.

Lipid droplets (LDs) have emerged as major regulators of cellular metabolism, encompassing lipid storage, membrane synthesis, viral replication, and protein degradation. Exclusive studies have suggested a direct link between LDs and cancer, as a notable abundance of LDs is found in cancerous cells. Therefore, monitoring the location, distribution, and movements of LDs is of paramount importance for understanding their involvement in biological processes. To target LDs, we designed and synthesized fluorophores with a styryl scaffold bearing electron-donating amino groups and pyridine-N-oxide, a zwitterionic acceptor moiety. We explored their photophysical properties in various solvents and conducted systematic DFT calculations on the synthesized fluorescent molecules, comparing them with neutral pyridine and cationic pyridinium styryl dyes. The results demonstrate that diphenylaminostyryl pyridine-N-oxide (TNO) shows excellent imaging of LDs, in contrast to the behavior of cationic styrylpyridinium (TNC), which primarily localizes within the mitochondria. Notably, pyridine N-oxide offers several benefits: an increased dipole moment facilitating charge separation between donors and acceptors, substantial HOMO and LUMO stabilization, improved water solubility, favorable redox properties, and bathochromic-shifted absorption/emission spectra, showing promise as a fluorescent tool for probing the cellular-biological realm.

Synthesis and Biological Evaluation of Amphotericin B Formulations Based on Organic Salts and Ionic Liquids against Leishmania infantum.

Nowadays, organic salts and ionic liquids (OSILs) containing active pharmaceutical ingredients (APIs) are being explored as drug delivery systems in modern therapies (OSILs-API). In that sense, this work is focused on the development of novel OSILs-API based on amphotericin B through an innovative procedure and the evaluation of the respective biological activity against Leishmania infantum. Several ammonium, methylimidazolium, pyridinium and phosphonium organic cations combined with amphotericin B as anion were synthesized in moderate to high yields and high purities by the water-reduced buffer neutralization method. All prepared compounds were characterized to confirm the desired chemical structure and the specific optical rotation ([α]D25) was also determined. The biological assays performed on L. infantum promastigotes showed increased activity against this parasitic disease when compared with the starting chloride forms and amphotericin B alone, highlighting [P6,6,6,14][AmB] as the most promising formulation. Possible synergism in the antiprotozoal activity was also evaluated for [P6,6,6,14][AmB], since it was proven to be the compound with the highest toxicity. This work reported a simple synthetic method, which can be applied to prepare other organic salts based on molecules containing fragile chemical groups, demonstrating the potential of these OSILs-AmB as possible agents against leishmaniasis.

Noncovalent Interactions in Halogenated Pyridinium Salts of the Weakly Coordinating Anion [Al(OTeF5 )4

The synthesis and the first structural characterization of the halogenated pyridinium salts [C5 F5 NH]+ , [C5 F4 ClNH]+ , [(C5 F5 N)2 H]+ , [(C5 Cl5 N)2 H]+ of the weakly coordinating anion (WCA) [Al(OTeF5 )4 ]- , showing noncovalent interactions in the solid state, are presented. The salts were characterized by the multinuclear NMR and IR spectroscopy as well as X-ray diffraction. Hirshfeld surface analysis and solid state structures reveal various intermolecular anion-π and σ-hole interactions between the corresponding halogenated pyridinium cations and the anion [Al(OTeF5 )4 ]- .

Extractive desulfurization of liquid hydrocarbon fuel: Task-specific ionic liquid development and experimental study

Extractive desulfurization has been used as an alternative method to remove sulfur compounds from liquid hydrocarbon fuels because of its simplicity and easy operating conditions. Ionic liquids (ILs) were applied as extractant solvent for extractive desulfurization, due to their unique properties. But the selection of proper cations and anions are still the most challenging parts of all researches. In the present study, a new methodology was developed for screening of cation and anion molecules to obtain maximum sulfur removal efficiency. At first, the best structural descriptors were selected using Genetic Algorithm. The different kinds of molecular descriptors for a diverse library of cation/anion have been evaluated, including 114 cations and 48 anions. Then, the most proper cations and anions have been selected using Principal Component Analysis (PCA) after evaluating the most accurate structural descriptors for various cations and anions. It was concluded that ionic liquids (ILs) comprise imidazolium and pyridinium cations with hexyl chain, combined with the [N(CN)2] and [Ac] anions, are promising ILs as extraction solvents for extractive desulfurization. To evaluate the obtained results, one of the selected ILs, 1-Hexyl-pyridinium dicyanamide ([Hpy][N(CN)2]), has been synthesized for the first time. The as-synthesized IL was characterized through NMR and FTIR analysis. After that, by investigating results, it is observed that the sulfur removal of [Hpy][N(CN)2] for DBT and BT is nearly 62% and 67%, respectively. Therefore, [Hpy][N(CN)2] is a proper solvent for extraction of DBT or BT from n-heptane.

Poly(norepinephrine) As a Functional Additive for Hybrid Cellulose/Agarose-Based Hydrogel Membranes: Application to Supercapacitors

A rapidly growing interest in renewable energy sources requires not only developing efficient energy storage systems but also incorporating a greater number of eco-friendly components. Electrochemical double-layer capacitors (EDLCs) are a class of energy storage devices capable to store the electrical charge due to the separation of oppositely charged ions in the electrical field which results in the formation of an electrical double layer (EDL) at the electrode/electrolyte interface. EDLCs consist in general of two porous carbon-based electrodes pre-soaked with electrolyte and separated with a membrane (separator). The simple electrostatic mechanism of energy storage, coupled with a lack of chemical changes and faradaic transitions during operation, results in high electrical capacitance compared to classical capacitors, significantly higher power density in contrast to batteries, and practically unlimited life span. Currently, commercial EDLCs typically rely on organic solvents, such as acetonitrile or propylene carbonate, with the addition of ionically-conductive salts. However, there are several drawbacks when it comes to practical applications involving particular low conductivity, toxicity, flammability and high cost. This resulted in an increased interest in aqueous electrolytes such as KOH, H2SO4 or simple inorganic salts, which although they have a limited potential window, exhibit many positive features including higher ionic conductivity, lower viscosity, increased safety, lower cost and ease of assembly under ambient atmosphere. Modern and technologically advanced charge storage devices often require high safety flexible and deformable devices for specific applications. However, at the current state-of-the-art, the EDLCs suffer from two prominent limitations (i) the possibility of electrolyte leakage and (ii) high standards of technology to safely encapsulate electrolytes in the device. Therefore, a lot of research is held to develop alternatives for currently used liquid (aqueous and organic) electrolytes. One of the solutions to overcome these limitations are solid-state EDLCs. Those systems use an ionically-conductive polymer or hydrogel membrane, which serves as both the separator and the electrolyte. Cellulose, built of β-(1→4)-linked D-glucose units, is one of the most prevalent and easily degradable biopolymers. Albeit, its wide availability, biodegradability and low cost, the usage of cellulose is limited due to insolubility in most common solvents. The recent alternative, to toxic and flammable organic compounds, such as N, N- dimethylformamide/N2O4, N-methylmorpholine oxide (NMMO), are ionic liquids (ILs), that have been gaining lately a lot of attention in energy storage systems. Various ILs based on imidazolium, pyridinium and ammonium cation paired with strongly basic anion (e.g., OAc-, HCOO-) were also recently used to dissolve cellulose. However, the requirements of high-purity syntheses and the cost of some of the cations/anions may affect a large scale application. Therefore, our research refers to an alternative route of chemical regeneration of microcrystalline cellulose, i.e. its dissolution using an aqueous mixture of NaOH/urea, and further processing into a hydrogel membrane in the presence of cross-linking agent epichlorohydrin. To improve the mechanical strength and electrolyte uptake, in-situ polymerized norepinephrine and agarose were subsequently incorporated obtaining an interpenetrating polymer network (IPN). The structure and morphology of the membranes were characterized with SEM/EDX, CP/MAS 13C-NMR, AT-FTIR, TGA, contact angle, and elementary analysis. The ionic conductivity was determined using impedance spectroscopy over a wide range of temperatures (5-60°C). The relation between stress and strain in the materials was also determined to diagnose the mechanical properties. The cellulose-based hydrogel membranes were further used as a support for various aqueous electrolytes, including H2SO4, Na2SO4, i.e. most commonly used for aqueous EDLCs. Also, the alternative electrolyte was used, i.e. silicotungstic acid, H4SiW12O40 which according to our recent results seems to be a promising candidate to replace conventional acidic electrolytes [1]. The designed systems were compared, in terms of energy, power and cycleability, with their analogues using conventional polypropylene separators and a liquid electrolyte.[1] N.H. Wisinska, M. Skunik-Nuckowska, S. Dyjak, P.J. Kulesza, Factors affecting the performance of electrochemical capacitors operating in Keggin-type silicotungstic acid electrolyte, Appl. Surf. Sci. 530 (2020) 147273, https://doi.org/10.1016/j.apsusc.2020.147273Acknowledgement Financial support was provided by the National Science Center under Preludium 19 grant no. 2020/37//N/ST4/01679. This work was implemented as a part of Operational Project Knowledge Education Development 2014–2020 co-financed by the European Social Fund, Project No POWR.03.02.00-00-I007/16-00 (POWER 2014-2020)

Constructing inorganic-rich solid electrolyte interphase via abundant anionic solvation sheath in commercial carbonate electrolytes

Lithium (Li) metal anode coupled with high-voltage cathode is critical for realizing high-energy storage. However, the organic-dominated solid electrolyte interphase (SEI) originating from carbonate electrolytes undergoes continuous cracking/reformation during cycling, leading to severe Li dendrite growth that hinders its practical application. Herein, we report an extremely soluble ionic liquid salt of pyridinium trifluoroacetate for constructing inorganic-rich SEI on Li in commercial carbonate electrolytes. Pyridinium cations (Py+) could be attached to the negatively-charged surface of Li due to electrostatic interaction and thereafter be decomposed into Li+-conductive nitrogen-containing components. Moreover, benefiting from the strong coordination of carbonyl (CO) and Li+, trifluoroacetate anions (TFA−) can prompt the dissolution of lithium nitrate (LiNO3) in carbonate electrolytes, thereby tuning the Li+ solvated shell. The formation of distinct solvation shell involving abundant anions is experimentally and theoretically demonstrated, which favors rapid desolvation kinetics. In addition, combined effect of additives facilitates the formation of additive-derived LiF-Li3N enhanced inorganic-rich SEI, significantly reducing the Li+ diffusion energy barrier and promoting compact chunky Li deposition. A thin and dense cathode electrolyte interphase (CEI) layer is generated in designed electrolyte and restrains dissolution of transition-metals. Consequently, superior cycling and rate performance of Li||NCM523 cells is achieved, confirming the enhanced stability.

2,4,6‐Trimethylpyridine‐Derived Vinylene‐Linked Covalent Organic Frameworks for Confined Catalytic Esterification

AbstractKnoevenagel condensation is a powerful tool for the construction of vinylene‐linked covalent organic frameworks. Herein, we established a concise approach to vinylene‐linked COFs by Knoevenagel condensation at the multi‐methyl groups of a pyridine ring through in situ formation of an N‐acyl pyridinium cation in the presence of various acylating reagents. Following this strategy, two vinylene‐linked COFs were constructed using 2,4,6‐trimethylpyridine and multi‐aldehyde‐substituted aromatic derivatives as monomers. The resultant COFs are highly crystalline and assembled into hexagonal lattices with specific surface areas as large as 1915 m2 g−1 (vs. 1972 m2 g−1 of the theoretical value). The stable and abundant pyridine‐decorated regular nanochannels within the COFs allow for catalyzing the esterification of several pharmaceutical intermediates with distinct spatially confined selectivity and recyclability, representing an environmentally friendly catalytic organic transformation.

New task-specific ionic liquids based on phenyl diazenyl methyl pyridinium cation: Energetic, electronic and optical properties exploration based on DFT calculations

Physicochemical properties of the three series of task-specific ILs formed from methyl pyridinium [MPy]+, phenyl diazenyl methyl pyridinium [DMPy]+ and functionalized diazenyl methyl pyridinium [X−DMPy]+ (X: NH2, OH, OCH3, CH3, C2H5, H, F, CHO, CN and NO2) cations and benzoate ([Y1]-), benzenesulfonate ([Y2]-), nitrate ([Y3]-) and tetra fluoroborate ([Y4]-) anions were investigated using density functional theory (DFT) calculations at M06-2X/AUG–cc–pVDZ level of theory. For the introduced task-specific ILs the structural parameters, energetic, electronic and topological characteristics were calculated and discussed using electrostatic maps and indexes of NBO, QTAIM, ECW and NCI. The effect of the type of anions, functional group, variation of the substituents on the functional group at cationic part on the interaction energy as well as some of their physical, chemical and optical properties are taking into account.

2,4,6-Trimethylpyridine-Derived Vinylene-Linked Covalent Organic Frameworks for Confined Catalytic Esterification.

Knoevenagel condensation is a powerful tool for the construction of vinylene-linked covalent organic frameworks. Herein, we established a concise approach to vinylene-linked COFs by Knoevenagel condensation at the multi-methyl groups of a pyridine ring through in situ formation of an N-acyl pyridinium cation in the presence of various acylating reagents. Following this strategy, two vinylene-linked COFs were constructed using 2,4,6-trimethylpyridine and multi-aldehyde-substituted aromatic derivatives as monomers. The resultant COFs are highly crystalline and assembled into hexagonal lattices with specific surface areas as large as 1915 m2 g-1 (vs. 1972 m2 g-1 of the theoretical value). The stable and abundant pyridine-decorated regular nanochannels within the COFs allow for catalyzing the esterification of several pharmaceutical intermediates with distinct spatially confined selectivity and recyclability, representing an environmentally friendly catalytic organic transformation.

Assay of MAO Inhibition by Chromatographic Techniques (HPLC/HPLC-MS).

Monoamine oxidase (MAO) enzymes (MAO A and B) catalyze the oxidative deamination of biogenic amines, neurotransmitters, and xenobiotic amines and contribute to the regulation of the contentof these activesubstances in mammalian organisms. The oxidation of biogenic amines by MAO produces hydrogen peroxide (H2O2) and aldehydes that represent risk factors for oxidative injury.The inhibitorsof MAO are useful as antidepressants and neuroprotective agents. Usually, the assays of MAO determine amine deamination products or measure the H2O2 released by using direct spectrophotometric or fluorimetric methods. Direct methods are more prone to interferences and can afford inaccurate results. Those limitations can beavoided by using chromatographic techniques. This work describesa chromatographic method to assay MAO A and MAOB activity by using kynuramine as a nonselective substrate and the subsequentanalysis of 4-hydroxyquinoline by RP-HPLC-DAD-fluorescence and mass spectrometry(MS). Alternatively, the assay uses the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxin as a substrate of MAO that is oxidized (bioactivated) to neurotoxic pyridinium cations which areanalyzed by HPLC. These methods are applied to assess the inhibition of MAO by bioactive β-carboline alkaloids occurring in foods, plants, and biological systems.

Porous ionic polymers as a photocatalyst: Self-assembly of donor-acceptor by regulating the valence state of photo-responsive groups

The world is on high alert against trace but extremely hazardous pollution of heavy metals and organic dyes in wastewater. Among various treatments, porous photocatalyst with dual functions of adsorptive enrichment and photodegradation are highly desirable yet challenging. Herein, we demonstrate a robust donor-acceptor (D-A) self-assembly by regulating the valence state of photo-responsive groups to construct porous ionic. The density function theory calculations reveal that the excitons induced on the neutral pyridine group (D) can be attracted by its neighboring cationic pyridinium one (A), thus the distinct charges separation and transfer enhancement can be realized in one PIP-based photocatalyst. Guided by this, a partially ionized pyridine-pyridinium (PB-PIPs) photocatalysts are fabricated, which show excellent adsorption capacity for the heavy metal Cr(VI) anion on pyridinium cations and rhodamine B (RhB) on the pyridine rings. Significantly, the target-adsorptions promote the accurate deliveries of excitons, that the simultaneous photocatalytic reduction of Cr(VI) and oxidation of RhB are achieved. The photodegradation performance of PB-PIPs under visible-light irradiation is superior to the state-of-the-art organic photocatalysts. Therefore, this convenient strategy of the valence state regulation provides a promising solution to the focus of synergistically visible-light harvesting, charges separating and transferring, and target-delivering in photocatalysis.

Extraction of Pb (II) and Co (II) using N,N-dioctylsuccinamate based room temperature ionic liquids containing aliphatic and aromatic cations

Synthesis and Characterization of six novel N,N -dioctylsuccinamate based room temperature ionic liquids (RTILs) bearing imidazolium, pyridinium, ester imidazolium, and quaternary ammonium cations is reported. Extraction of Pb(II) and Co(II) by these RTILs has been investigated. Ionic liquids (ILs) synthesized were [C 4 mim][N 88 SA] , [C 8 mim][N 88 SA], [C 4 Py][N 88 SA], [C 8 Py][N 88 SA], [α-mim-ester][N 88 SA] and [N 2244 ][N 88 SA] termed as L1, L2, L3, L4, L5 and L6 respectively. Liquid-liquid extraction was performed and all the six systems showed excellent extractability results for both Pb(II) and Co(II). During the process of extraction several factors i.e., nature of cation, pH of the aqueous phase, equilibration time, and initial metal ion concentration were investigated. The extraction efficiency of above 98 % for all types of extractants was observed. The nature of cation its concentration, equilibration time, and pH of the aqueous phase significantly influenced the extraction efficiency. Maximum extraction was observed at pH values between 4 and 8 and optimum contact time was observed to be 40–45 min. Increasing the metal ion concentration decreased the extraction efficiency. The extraction efficiency of both metal ions decreased in the order [N 88 SA][C 8 mim] (L2) > [α-mim-Ester][N 88 SA] (L5) > [N 88 SA][C 4 mim] (L1). This is evident from the order of extraction behaviour that increasing the bulkiness of cation, results in stronger complexation, hence increasing extraction.

A clickable AIEgen for visualization of macrophage-microbe interaction

Visualization of immunocyte-microbe interaction is of great importance to reveal the physiological role and working mechanism of innate and adaptive immune system. The lack of rapid and stable microbial labeling platform and insufficient understanding of macrophage-microbe interaction may delay precautions that could be made. In this contribution, a clickable AIEgen, CDPP-NCS, containing a cationic pyridinium moiety for targeting bacteria and an isothiocyanate moiety for covalently bonding with amine groups, is successfully developed. With the advantages of excellent photostability and rapid bioconjugation with amine groups on the bacterial envelope, the processes of macrophage-bacterium interactions with subcellular resolution has been successfully captured using this clickable AIE probe. Therefore, the new clickable AIEgen is a powerful tool to study the interaction between cell and bacterium.

Synthesis of Microporous Aluminosilicate by Direct Thermal Activation of Phenyl-Substituted Single-Source Aluminosilicate Molecular Precursors.

The construction of aluminosilicates from versatile molecular precursors (MPs) represents a promising alternative strategy to conventional processes based on monomeric molecular or polymeric Al and Si sources. However, the use of MPs often suffers from drawbacks such as the decomposition of the core structures in the presence of solvents, acids, or bases. In this work, we demonstrate a simple thermal synthesis of porous aluminosilicates from single-source spiro-7-type MPs that consist of a tetrahedral Al atom and six Si atoms functionalized with 12 phenyl (Ph) groups, (C+)[Al{Ph2Si(OSiPh2O)2}2]- (C+[AlSi6]-; C+ = pyridinium cation (PyH+), Na+, K+, Rb+, or Cs+), without using a solvent or activator. Microporous aluminosilicates synthesized via the thermal treatment of C+[AlSi6]- under a 79% N2 + 21% O2 atmosphere exhibited extremely low carbon contents (0.10-1.28%), together with Si/Al ratios of 3.9-6.7 ± 0.2 and surface areas of 103.1-246.3 m2/g. The solid-state 27Al and 29Si MAS NMR spectra suggest that the obtained aluminosilicates with alkali cations retain a tetrahedral Al site derived from the spiro-7-type core structure. After a proton-exchange reaction, the aluminosilicates showed almost 1.5 times higher reactivity in the catalytic ring-opening of styrene oxide than the aluminosilicate before proton exchange due to the catalytically active OH site being predominantly bridged by tetrahedral Al and Si atoms. These results suggest that the present MP strategy is a promising method for the introduction of key structures into active inorganic materials.

Synthesis and characterisation of ionic liquid crystals based on substituted pyridinium cations

ABSTRACT Novel ionic liquid crystals based on pyridinium and methylpyridinium cations with a dodecyl chain and bromide as anion have been prepared and characterised. [C12Pyr][Br] and [C12-n-Pic][Br] (n = 2, 3 or 4) were studied in order to understand the influence of the methyl group position in the mesomorphic behaviour. Neat microwave-assisted reactions were carried out to synthesised [C12Pyr][Br], [C12-3-Pic][Br] and [C12-4-Pic][Br] as a sustainable approach, leading to significantly reduced reaction times (35 min vs. 48 h in conventional method). All prepared compounds were characterised by spectroscopic techniques (1H and 13C-NMR; ATR-FTIR), Elemental Analysis, Differential Scanning Calorimetry (DSC), Polarised Optical Microscopy (POM) and X-Ray Powder Diffraction (XRD). It was observed that the presence of water highly influences the phase transformations. Nevertheless, thermotropic smectic phases were detected for all materials with a layer spacing between 20 and 35 Å, compatible with a bilayer interdigitated or tilted lamellar arrangement of the cation’s alkyl chain. This work also indicates new routes for preparing ionic liquid crystals with various functionalities ruled by the synthesis design.

Growth and characterization of nitrophenol complexes with piperazine and pyridine derivatives

1-amino-4-methyl piperazine bis (4-nitrophenol) (1A4MP4N) and 2-amino-5-methyl pyridinium 4-nitrophenolate 4-nitrophenol (2A5MP4N) have been grown as single crystals using slow evaporation solution growth technique at room temperature. The grown crystals were characterized by single crystal X-ray diffraction and its lattice parameters were determined. 1A4MP4N and 2A5MP4N were crystallized in monoclinic crystal system with P21/n and Cc space group respectively. In 1A4MP4N, piperazine ring possesses inversion symmetry and has a chair conformation. Piperazine ring linked to 4-nitrophenol molecule through O3-H3D···N2 hydrogen bond forms C(5) chain motif. In 2A5MP4N, N1 atom in 2-amino-5-methyl pyridinium cation is connected with 4-Nitrophenolate anion through N1-H1···O11 hydrogen bond thus forms C(12) chain motif. Hirshfeld surface mapping analysis is carried out for both crystal structures. The fingerprint plot for H···H intermolecular contacts cover a major portion (41 %) of the Hirshfeld area of 1A4MP4N and O···H (35.7%) intermolecular contacts play a major role in 2A5MP4N. The Taucs plot reveals that band gaps of 1A4MP4N and 2A5MP4N are 2.66 eV and 5.18 eV respectively. From Z-scan technique the third order nonlinear optical susceptibility is found to be χ3 = 1.21322 × 10−9 esu and 1.75752 × 10−9 for both crystals.

Enhancing Mechanical Performance of a Polymer Material by Incorporating Pillar[5]arene-Based Host-Guest Interactions.

Polymer gels have been widely used in the field for tissue engineering, sensing, and drug delivery due to their excellent biocompatibility, hydrophilicity, and degradability. However, common polymer gels are easily deformed on account of their relatively weak mechanical properties, thereby hindering their application fields, as well as shortening their service life. The incorporation of reversible non-covalent bonds is capable of improving the mechanical properties of polymer gels. Thus, here, a poly(methyl methacrylate) polymer network was prepared by introducing host–guest interactions between pillar[5]arene and pyridine cation. Owing to the incorporated host–guest interactions, the modified polymer gels exhibited extraordinary mechanical properties according to the results of the tensile tests. In addition, the influence of the host–guest interaction on the mechanical properties of the gels was also proved by rheological experiments and swelling experiments.

Thermal stability limits of imidazolium, piperidinium, pyridinium, and pyrrolidinium ionic liquids immobilized on metal oxides

Twenty-nine different ionic liquids (ILs) consisting of imidazolium, pyridinium, piperidinium, and pyrrolidinium cations and I–, Cl–, Br–, PF6–, BF4–, [DCA]–, and [NTf2]– anions were immobilized on MgO and SiO2. Their short-term thermal stability limits were investigated by thermogravimetric analysis and compared with those of the corresponding bulk ILs. Data showed that the thermal stability limits of ILs change significantly when the ILs are immobilized on metal oxides. These changes were evaluated based on the structural interactions determined by infrared (IR) spectroscopy. Systematic structural differences were considered to investigate the factors affecting the thermal stability of bulk ILs, and their counterparts immobilized on MgO and SiO2. These structural changes were the change in the alkyl chain length, the methylation on C2 site in imidazolium ILs, the change in substituent position in the pyridinium ring, the change in the anion, and the change in the IL family. The strongest factor controlling the thermal stability limits of both bulk ILs and their supported counterparts was determined as the anion type. Accordingly, the basicity of the anion and the surface acidity of the metal oxide and their resulting interactions were found to have a significant effect on the thermal stability limits. Data presented here offer the opportunity to pick a suitable anion and cation pair according to the metal oxide, so that the supported IL can withstand the desired operation conditions in various applications, such as catalysis or gas separation.