Cation Pairs Research Articles

Synthesis and physical characteristics of narrow bandgap chalcogenide SnZrSe3

Background: The development of organic/inorganic metal halide perovskites has seen unprecedent growth since their first recognition for applications in optoelectronic devices. However, their thermodynamic stability and toxicity remains a challenge considering wide-scale deployment in the future. This spurred an interest in search of perovskite-inspired materials which are expected to retain the advantageous material characteristics of halide perovskites, but with high thermodynamic stability and composed of earth-abundant and low toxicity elements. ABX3 chalcogenides (A, B=metals, X=Se, S) have been identified as potential class of materials meeting the aforementioned criteria. Methods: In this work, we focus on studying tin zirconium selenide (SnZrSe3) relevant physical properties with an aim to evaluate its prospects for application in optoelectronics. SnZrSe3 powder and monocrystals were synthesized via solid state reaction in 600 – 750 °C temperature range. Crystalline structure was determined using single crystal and powder X-ray diffraction methods. The bandgap was estimated from diffused reflectance measurements on powder samples and electrical properties of crystals were analysed from temperature dependent I-V measurements. Results: We found that SnZrSe3 crystals have a needle-like structure (space group – Pnma) with following unit cell parameters: a=9.5862(4) Å, b=3.84427(10) Å, c=14.3959(5) Å. The origin of the low symmetry crystalline structure was associated with stereochemical active electron lone pair of Sn cation. Estimated bandgap was around 1.15 eV which was higher than measured previously and predicted theoretically. Additionally, it was found that resistivity and conductivity type depended on the compound chemical composition. Conclusions: Absorption edge in the infrared region and bipolar dopability makes SnZrSe3 an interesting material candidate for application in earth-abundant and non-toxic single/multi-junction solar cells or other infrared based optoelectronic devices.

Thermally Activated Aromatic Ionic Dopants (TA‐AIDs) Enabling Stable Doping, Orthogonal Processing and Direct Patterning

AbstractDoping plays a critical role in organic electronics, and dopant design has been central in the development of functional and stable doping. In this study, there is departure from conventional molecular dopants and a new class of dopants are reported – aromatic ionic dopants (AIDs). AIDs consist of a pair of aromatic cation and anion that are responsible for molecular doping reaction and charge balancing separately. It is shown that the first AID made from cycloheptatrienyl (tropylium) cation and pentacyanocyclopentadienide anion (PCCp), abbreviated as T‐PCCp, can function as an effectivep‐type dopant to dope polydioxythiophenes. Here, tropylium cation induces the doping reaction while the PCCp anion stabilizes the generated polarons and bipolarons. With T‐PCCp, a highly doped (≈120 S/cm) and stable system is achieved up to 150 °C, an orthogonal (sequential)solution processing resulting from the immiscibility of the dopant and the polymer host, and a high‐resolution direct micropatterning with laser writing resulted from a thermally activated doping process.

Ionic crosslinking of alginate/carboxymethyl chitosan fluorescent hydrogel for bacterial detection and sterilization

Herein, a polysaccharide-based fluorescent hydrogel with multi-responsiveness simply implemented by concurrent effects of ionic crosslinking/rehydration processes is presented. Specifically, the alginate and carboxymethyl chitosan are chosen to prepare the interpenetrating polymer matrix while a pair of metal cations has been selectively sequentially integrated to alter hydrogel mechanical and fluorescent properties. Experimental results indicate the hydrogels show tunable fluorescent emission in response to multiple cations and pH conditions, and display a reversible “ON/OFF” fluorescent response to Mn+/ethylenediaminetetraacetic acid. Moreover, this synergistic ionic crosslinking strategy is proved to be highly effective in preparing multifunctional metallohydrogels possessing robust/anisotropic mechanical properties, typical shape memory and cation/pH-responsive fluorescence performance, and a proof-of-application for bacterial detection and sterilization has also been demonstrated. Therefore, we believe this study would provide new insights into multifunctional luminescent hydrogels for advanced biomedical systems.

XANES in the C K, N K, O K, and F K regions of ionic liquids composed of imidazolium-based cations with bis(trifluoromethylsulfonyl)amine anion or bromide anion

To clarify the electronic structures and obtain the association structures of ionic liquids (ILs), X-ray absorption near-edge structure (XANES) spectra in the C K, N K, O K, and F K regions of a systematic series of ILs were measured. The C K-XANES spectra were theoretically analyzed using density functional theory (DFT) calculations. Focusing on the cation-size-effects on the electronic structure, target ILs were chosen as pairs of imidazolium (Im) cations with various alkyl substituents (Cx,y) and anions of bromide (Br) or bis(trifluoromethylsulfonyl)amine anion (TFSA). Subtracting the measured XANES as [CxCyIm]TFSA – [CxCyIm]Br suggested that multi-ion interactions on the C atoms in Im with shorter substituents were stronger than those in Im with longer substituents. Additionally, fewer multi-ion interactions were observed on the N, O, and F atoms than the C atom. By comparing the calculated XANES spectra of the cation-anion pair models, the measured C K-XANES profiles were assigned to the corresponding component C atoms. However, the measured strong multi-ion interactions on the C atoms could not be reproduced by the DFT calculations of the simple cation-anion pair models. This means that XANES analysis for C atoms in smaller Im cations should be considered as aggregated structures composed of various multi-ion clusters.

Crystallization, structural study and analysis of intermolecular interactions of a 2-aminobenzoxazole–fumaric acid molecular salt

The new organic salt, 2-aminobenzoxazol-3-ium 3-carboxyprop-2-enoate, C7H7N2O+·C4H3O4 −, of the two bioactive compounds 2-aminobenzoxazole and fumaric acid, crystallizes in the orthorhombic space group Pbca using classical evaporation of their solution in water. The usual topological analysis revealed four classical (N—H...O and O—H...O) and two non-classical (C—H...O) hydrogen bonds in the structure. Stacking was found as well for a pair of 2-aminobenzoxazolium cations. A Hirshfeld surface analysis including the two-dimensional fingerprint plots was performed to define the residual π–π interactions and to quantify the influences of different types of interactions by means of topological analysis. Analysis of the pairwise interaction energies was used to prove the formation of the corrugated paired layers of cation–anion dimers parallel to the plane (001) as a basic structural motif in the topological, as well as in the energetic structure of the crystal. It showed that the layers are connected by the hydrogen bonds inside and by stacking and π–π interactions and general dispersion between them.

Intermolecular adsorption-pairing synergy for accelerated polysulfide redox reactions towards lithium-sulfur battery with high stability

Rational design of heterostructure which integrate adsorption and catalysis has been considered as an effective method for shuttle effect and slow kinetics of polysulfides. However, the synergy involved in most studies requires the transfer of polysulfides (Li2Sx, 4 ≤ x ≤ 8) from one site to another relatively distant site, which is low-efficient and slow. Herein, a novel synergistic strategy (adsorption-pairing) is proposed for the first time to promote polysulfides conversion by tight intermolecular synergy. We speculate that amide groups adsorb polysulfides first, and then the anchored polysulfides are paired with the adjacent zwitterionic structures to form two cation-anion pairs (imidazole ring[+]-Sx2−[-] and Li+[+]-sulfonate[-]). Unique ion pairing could elongate the Li-S bonds from two directions at the same time. The synergistic process between close groups ensures that the anchored polysulfides could be further catalyzed and anchoring site could be vacated for the unanchored polysulfides, which is efficient and fast. The Li-S batteries exhibits outstanding cycling performance over 500 cycles with the capacity retention of 91.4% and favorable rate capability up to 4 C. This work provides a new insight in the synergistic effect for integrated adsorption and catalytic ability and constructs an ideal interfacial environment to lithium-sulfur chemistry.

π-Stacked Ion Pairs: Tightly Associated Charged Porphyrins in Ordered Arrangement Enabling Radical-Pair Formation.

π-Electronic ion pairs are of interest for fabricating electronic materials that use intermolecular interactions based on electrostatic and dispersion forces, defined as iπ-iπ interactions, to provide dimension-controlled assemblies. Porphyrin ions, whose charge is delocalized in the core units, are suitable for ordered arrangement and assemblies by ion pairing. Herein, charged porphyrins were found to form solid-state assemblies and solution-state stacked ion pairs according to the peripheral electron-donating groups (EDGs) and electron-withdrawing groups (EWGs). The concentration-dependent 1H NMR signal shifts of a porphyrin ion pair, comprising a meso-EWG cation and a meso-EWG anion, provided a hetero-dimerization constant of 2.8 × 105 M-1 in CD2Cl2 at 20 °C. In the ion pair of a meso-EWG cation and a meso-EDG anion, the electron transfer in the steady and excited states according to solvent polarity and photoexcitation, respectively, produced the radical pairs. The electron spin resonance analysis in frozen toluene revealed the formation of a heterodiradical in a closely stacked structure by the antiferromagnetic dipolar interaction and temperature-dependent spin transfer behavior.

Morpholin-4-ium [5-cyano-6-(4-methylphenyl)-4-(morpholin-4-yl)pyrimidin-2-yl](phenylsulfonyl)amide

In the title molecular salt, C4H10NO+·C22H20N5O2S−, pairs of anions are linked by pairs of morpholinium cations through N—H...N and bifurcated N—H...(O,N) hydrogen bonds. Every cation donates two such bonds, one to each of the neighbouring pair of cations, generating centrosymmetric tetramers.

Design of novel dual functional ionic liquids and DFT study on their CO2 absorption mechanism

Dual functional ionic liquids with the combinations of diethylenetriamine cation ([DETAH]+) or 1-ethanolamine-ethylenediamine cation([1-AOEt-EDAH]+) and 4-fluorobenzoate anion ([4-F-PhO]−) were explored for efficient CO2 capture in this work, and the absorption mechanisms of isolated ions and ion pairs were investigated using the dispersion corrected density functional theory (DFT) method. Above all, the possible reaction sites and reaction activity of TSILs were inferred by electrostatic potential (ESP) and Frontier molecular orbital analysis, then the reaction pathways for absorbing CO2 were proposed, and the transition state search of each elementary reaction by cation, anion and ion pair absorption was performed. Furthermore, the Gibbs free energy and reaction heat of each path were separately calculated, and the Gibbs free energy barrier and enthalpy barrier diagrams were drawn. In addition, the change of structural parameter, bond order and ADCH charge of reactants (R), transition states (TS), intermediates (IM), and products (P) were compared. The results showed that the absorption reaction of [DETAH]+ was the most likely to occur in kinetics, while that of [1-AOEt-EDAH]+ was favorable in thermodynamics. For the [DETAH][4-F-PhO], ion pair binding competed strongly with the CO2 chemisorption, while for [1-AOEt-EDAH][4-F-PhO], anions improved the stability of the whole structure, leading to the decrease of the Gibbs free energy barrier. Hopefully, the results of this work are helpful to provide a theoretical basis for designing of novel functional ionic liquids.

Bis(1,2,3-trimethylpyridinium) Octa(μ2-bromido)Tetrabromidopentacuprate(II): Linear, Quasi-Planar Pentacopper(II) Oligomers Stacked to Form Egg-Tray Layers

The crystal structure of (1,2,3-trimethylpyridnium)2Cu5Br12 provides the second reported example of a fully halogenated, linear, quasi-planar, bibridged pentacopper(II) oligomer. The oligomers are aggregated into crosshatched layers that defy traditional notions and notations for quasi-planar oligomer stacking. The regularly arranged voids in the layers are occupied by inversion-related organic cation pairs similar to eggs in an egg-tray. The cross-hatched layer structure arises from a particular stacking of mixed organic cation/pentacopper oligomer sheets. The sheets consist of oligomers placed in a herringbone arrangement separated by zipper-like ribbons of organic cations in a structural motif similar to that found in other 1,2,3- or 1,2,6-trimethylpyridinium halidocuprate(II) structures. Alternative stacking of the sheets leads, on the other hand, to a conventional stacking pattern that conforms to traditional stacking descriptions. Interpretation of these structures in terms of the stacking of mixed cation/anion sheets, as is often performed for ABX3 systems, provides a complementary method for understanding these structures as well as providing a means to describe systems that are not easily described by traditional stacking notation.

Effect of iron redox ratio on the structures of boroaluminosilicate glasses

AbstractIron oxide is commonly found in natural or industrial glass compositions and can exist as ferrous (Fe2+) or ferric (Fe3+) species, with their ratios depending on glass composition, temperature, pressure and the redox reactions during the glass forming process. The iron redox ratio plays an important role on silicate glass structures and consequently various properties. This work aims to study the effect of iron oxide, and particularly the iron redox ratio, on the structures of borosilicate and boroaluminosilicate glasses using molecular dynamics simulations with newly developed iron potential parameters that are compatible with the borosilicate potentials. The results provide detailed cation coordination states of both iron species and the effect of redox ratio on boron coordination and other structural features. Particularly, competition for charge compensating modifier cations (such as Na+) among the fourfold‐coordinated cations such as B3+, Al3+, and Fe3+ is investigated by calculating the cation–cation pair distribution functions and coordination preferential ratios. The results show that the trivalent ferric ions, with a shorter Fe–O bond distance and better defined first coordiation shell with mainly four‐fold coordination, act as a glass former whereas the divalent ferrous ions mainly play the role of glass modifier. The ferrous/ferric ratio (Fe2+/Fe3+) was found to affect the glass chemistry and hence glass properties by regulating the amount of four‐coordinated boron, the fraction of non‐briding oxygen and other features. The results are compared with available experimental data to gain insights of the complex structures and charge compensation schemes of the glass system.

Synthesis and crystal structure of ebastinium hydrogen fumarate.

The structure of ebastinium hydrogen fumarate {systematic name: 1-[4-(4-tert-butyl-phen-yl)-4-oxobut-yl]-4-(di-phenyl-meth-oxy)piperidin-1-ium (E)-3-carb-oxy-1-hy-droxy-prop-2-en-1-olate}, C32H40NO2 +·C4H3O4 -, a 1:1 salt formed in the reaction between ebastine and fumaric acid is presented. All examined crystals were found to be twinned by pseudo-merohedry. The structure is extensively disordered, with over half (20 out of 35) its non-hydrogen atoms modelled as lying over two sets of sites. In the crystal, cation-anion pairs are linked by a strong N-H⋯O hydrogen bond [N⋯O = 2.697 (11) Å]. These units inter-act via weaker C-H⋯O and C-H⋯π contacts to form layers lying parallel to the bc plane. The hydrogen fumarate anions are linked by a very short O-H⋯O hydrogen bond [O⋯O = 2.5402 (17) Å], augmented by weak C-H⋯O contacts into pairs of R 2 2(6) ring motifs to form chains that extend parallel to the b-axis direction. Comparisons to similar crystal structures are presented.

Chemical Variants of the Dicyanamide Anion, and a Landscape for Basic and Superbasic Ionic Liquids

We describe the properties of three new aprotic ionic liquids (ILs) with irreducible cations and anions which are close relatives of the commonly used −N(CN)2 anion, namely −N(CHO)2 (diformylamide) and −N(CO)2(CH2)2 (succinimide), having pK a values which are slightly more basic than the pK a of OH− ions of aqueous solution chemistry. In addition to using the well-known N-butyl-N-methyl pyrrolidinium cation, P14 +, we report the use of the tetrabutylammonium cation, +N[CH3(CH2)3]4, in forming an ionic liquid with the diformylamide anion. The formation and purity of these ILs was assessed by 1H NMR spectroscopy. The broadband dielectric spectra for all three ionic liquids were analyzed and the glass transition temperatures (T g) estimated from the dielectric data matched well with those obtained from differential scanning calorimetry. The results demonstrate that pure aprotic ILs with high-pK a equivalent anions can be obtained by metathesis reactions despite their low pK a difference of 2 to 3. By contrast, protic analogues of these cation-anion pairs would fail to produce ILs, for which larger pK a differences are required. These new aprotic ILs are glass-forming with T g’s near 210 K and show DC-conductivities near 0.1 mS cm−1 at ambient temperatures.

Ionic Clathrate Hydrates of Tetraalkylammonium/phosphonium Salts: Structures, Properties, Some Applications, and Perspectives

Ionic clathrate hydrates (ICHs) belong to one of the groups of a wide class of clathrate hydrates. In the crystal structures of ICHs, cation–anion pairs of guest molecules, typically tetraalkylammonium/phosphonium salts, are included into the host framework of hydrogen-bonded water molecules. Because of their suitable phase change temperature and latent heat, ICHs are considered as promising phase change materials for application in cold energy storage and transportation. The presence of vacant cavities in ICHs structures, which can incorporate small gas molecules such as, for example, H2, CH4, CO2, N2, H2S, determines the possibility of their use for the separation and storage of gases. The formation of these double ICHs occurs under much milder pressure and temperature conditions compared to the pure gas hydrates of the same gases. Studying of the structural characteristics and thermophysical properties of ICHs and double ICHs with gases is the necessary basis for their effective applications in different practical ends. This work reviews information related to the new details and features of the structures of ICHs and double ICHs with gases revealed over the last decade or a little more as well as some thermophysical data such as hydrate numbers, temperatures and enthalpies of dissociation. This review focuses only on ICHs of tetrabutyl-, tetraisoamylammonium (TBA, TiAA), and tetrabutylphosphonium (TBP) salts, which are the most common representatives of this class of compounds. One of the sections is devoted to ICHs of TBA and TiAA with polymeric anions such as cross-linked polyacrylates. The purpose of the present paper is to review the studies that have been relatively little addressed in previous works.

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.

Structural, vibrational and thermal study of Bis(4-Carboxyanilinium) sulphate a new organo-sulphate adduct of 4-amino benzoic acid

Bis(4-carboxyanilinium) sulphate (B4-CASO4), a new organo-sulphate adduct of 4-amino benzoic acid, was synthesized and characterized by single-crystal X-ray diffraction, DSC and FTIR. B4-CASO4 crystallises in the monoclinic space group, P21/c, Z = 4, with two 4-CA cations and a sulphate anion in an asymmetric unit. These cations, 4-CA was found to exist as a cyclic acid dimer. In B4-CASO4 crystal the 4-CA cations and sulphate anions are connected through a three-dimensional network of strong charge-assisted N–H…O and C–OH…O hydrogen bonds. The infrared vibrational frequencies of B4-CASO4 were assigned and comparison of the spectral features of 4-ABA and B4-CASO4 suggest presence of a stronger NH…O and C–OH…O hydrogen bond interactions in B4-CASO4. Using the computational tool of energy framework analysis, the intermolecular interaction topology has been quantitatively analysed. A very high values of interaction energies are found for the hydrogen bonded anion-cation pairs in the crystal structure of B4-CASO4. The DSC, IR and computational results corroborate well with the structural data of B4-CASO4.

Chemical Characteristics of Surface Water of Sumpil River and Groundwater on its Surroundings

The objective of this study was to know the chemical characteristics of surface water in a segment of Sumpil River and the groundwater on its surrounding. The location of this study was in 3 cross sections, consisting of 1 well on the right of the Sumpil River, 1 well on the left of the Sumpil River flow, and 1 point on the Sumpil River flow. The chemical characteristics of the water were determined by the concentrations of cations and anions in the water sample using the Piper Trilinear Diagram with the GW Chart 1.30 computer program. Based on the results of the study, it was shown that the chemical characteristics of the Sumpil River water and the groundwater at the location of this study were the same, where all water samples had an alkaline earth metals content over the alkali content (zone 1), had a strong acidic content exceeding the weak acidic content (zone 4), have a balanced cation and anion pairs, none of which exceed 50% (zone 9), and shown that all of the water in the location of this study were fresh water.

Effect of Ion Pair on Contact Angle for Phosphonium Ionic Liquids.

The wettability of ionic liquids (ILs) is relevant to their use in various applications. However, a mechanistic understanding of how the cation-anion pair affects wettability is still evolving. Here, focusing on phosphonium ILs, wettability was characterized in terms of contact angle using experiments and classical molecular dynamics simulations. Both experiments and simulations showed that the contact angle was affected by the anion and increased as benzoate < salicylate < saccharinate. Further, the simulations showed that the contact angle decreased with increasing cation alkyl chain length for these anions paired with five different tetra-alkyl-phosphonium cations. The trends were explained in terms of adhesive and cohesive energies in the simulations and then correlated to the atomic scale differences between the anions and the cations.

Scaling Up the Simultaneous Production of Clean Electricity and Clean Water

The desalination fuel cell (DFC) is a nascent technology for co-production of clean electricity and water from a single cell, driven by the hydrogen-oxygen redox couple. Previously, DFCs employed a single cation and anion exchange membrane pair, and demonstrated desalination of feedwaters of 30 g l−1 NaCl while generating up to 8.6 kWh per m3 of desalinated water. Here, we propose and demonstrate a scaling strategy for DFCs, by adding additional alternating anion and cation exchange membrane pairs. Such a strategy is supported by previous measurements showing small potential loss across membranes in DFCs relative to that at the electrodes. We characterize and compare three cell configurations, including single, double or triple membrane pairs. We show that adding membrane pairs maintains the desalination performance of our DFC, while only moderately reducing cell power density. In addition, adding membrane pairs enables increased flexibility in the choice of anolyte and catholyte solutions, as these are no longer the primary brine channels. We show that optimizing the anolyte and catholyte enables a record power density of up to 10 mW cm−2 during desalination. We further develop and implement expressions for quantification of the thermodynamic energy efficiency of a multiple-membrane-pair DFC.

Electron ionisation of cyanoacetylene: ionisation cross sections and dication formation

Cyanoacetylene (HC3N) is an important trace species in the atmosphere of Titan. We report, for the first time, absolute partial electron ionisation cross sections and absolute precursor-specific partial electron ionisation cross sections for cyanoacetylene, following an experimental and computational investigation. Our methodology involves using 2D ion–ion coincidence mass spectrometry to generate relative cross sections, over the electron energy range 50–200 eV. These relative values are then normalised to an absolute scale, using a binary encounter-Bethe (BEB) calculation of the total ionisation cross section. The BEB calculation agrees well with previous determinations in the literature. The mass spectrometric observations of HC2N+ and HCN+, ions with a connectivity markedly different to that of the neutral molecule, point towards a rich cationic energy landscape possessing several local minima. Indeed, [HC3N]2+ minima involving a variety of cyclic configurations are revealed by a preliminary computational investigation, along with two minima with linear and bent geometries involving H atom migration (CCCNH2+). Determination of the energy of a transition state between these local minima indicates that the dication is able to explore the majority of this rich conformational landscape at our experimental energies. This investigation of the energetics also determines an adiabatic double ionisation energy of 30.3 eV for the lowest lying singlet state of HCCCN2+, and 30.1 eV for the lowest-lying triplet state. The bulk of the cation pairs detected in the coincidence experiment appear to originate from markedly excited dication states, not the ground state. We observe 5 two-body dissociations of HCCCN2+, and subsequent decay of one of the ions generated in such two-body processes accounts for the majority of three-body dissociations we observe.