Interionic Interactions Research Articles

Understanding the Mid-Infrared Spectra of Protic Ionic Liquids by Density Functional Theory.

Protic ionic liquids (PILs) are promising candidates as electrolytes for proton exchange polymer membrane fuel cells. In order to optimize their properties, a detailed understanding of the molecular interactions within the bulk and at the electrode-electrolyte interface is needed, which can be obtained by infrared spectra. A prerequisite for extracting information on the molecular structure and inter- or intramolecular interactions from an experimental spectrum is a reasonable interpretation of the observed spectral features. Here, we employed density functional theory to understand the vibration modes of PILs composed of ammonium cations and different counteranions. Different from the previous calculation methods performed on small cluster model systems consisting of isolated species, a periodically repeated system of four ion pairs was used in order to approximate the bulk liquid environment. The computed frequencies and IR intensity match well with the corresponding experimental spectra, allowing for its proper interpretation, especially the characteristic features of the interionic interaction. The presented approach enables accurate computation of a variety of ionic liquid systems in a highly efficient way.

Double pseudo-polymeric complexes of [Au(S2CNBu2)2][AgCl2] and [Au(S2CNHm)2]3[AgCl2][Ag0.59Au0.41Cl2]2: Preparation, supramolecular self-assembly, thermal behaviour and anti-mycobacterial activity

Pseudo-polymeric double complexes of [Au{S2CN(C4H9)2}2][AgCl2] (1) and [Au{S2CN(CH2)6}2]3[AgCl2][Ag0.59Au0.41Cl2]2 have been obtained and chemically identified using solution (1H, 13C{1H}) NMR and FT-IR spectroscopy. According to XRD analysis, it was established that both of the above crystalline compounds form complicated supramolecular architectures. Self-assembly and structural stabilization of these supramolecular formations are achieved due to numerous secondary interactions: Ag⋯S, Cl⋯S (in 1, 2) and Au⋯Cl, Au⋯S (in 2), which arose between the ionic structural units of the complexes. The combined manifestation of these interionic secondary interactions leads to the construction of two types of pseudo-polymeric chains of (⋯[Au(S2CNBu2)2]⋯[AgCl2]⋯)n (1) and (⋯[Au2(S2CNHm)4]⋯ [AgCl2]⋯)n (2). To study the thermal behaviour of the prepared compounds, the simultaneous thermal analysis (STA) technique was used, which allowed us to determine the conditions for the quantitative recovery of bound metals. Moreover, a high in vitro biological activity for each of the prepared gold(III)-silver(I) compounds against the non-pathogenic strain Mycolicibacterium smegmatis was experimentally revealed.

Refractive Laser Beam Measuring Diffusion Coefficient of Concentrated Battery Electrolytes

A thorough understanding of electrolyte transport properties is crucial in the development of alternative battery technology. As a key parameter, the diffusion coefficient offers important insights into the behavior of electrolytes, especially for fast charge of high-energy batteries. Existing methods of measurement are often limited by redox species or offer questionable accuracy due to side reactions and/or disruption of the diffusion profile. A highly sensitive optical method was developed using a refractive laser beam through triangular diffusion column to measure the diffusion coefficient of concentrated battery electrolytes. The method based on Snell’s law can be applied to all liquid phase electrolytes since the refractive index is concentration dependent for all liquid electrolytes. This universal method relies on the deflection of a refractive laser beam passing through an electrolyte of a minor concentration gradient in a triangular diffusion column (Figure 1). A polarized HeNe laser was arranged to pass the beam through a right-angled triangular quartz precision cell, slightly rotated to the normal. The exact position of the refracted beam was located by a silicon photodiode-based position detector. Deflection calibration curves made simple conversion of beam position to concentration, and during the diffusion of two layered solutions, data points were collected every minute to produce a concentration profile descriptive of the 48-hour diffusion. Diffusion coefficients were calculated using a model based on OSM theory, accounting for multi-component concentrated systems in a restricted diffusion column.1 The measured diffusion coefficients are between 4.12x10-10 m2/s for 0.15 mol/kg ZnSO4 and 0.681x10-10 m2/s for 2.5 mol/kg ZnSO4 at 22.4 °C. The profile of concentration-dependent diffusion coefficients follows a non-linear inverse relationship described by the function D=4.943(1+m)-1.564 (Figure 2).Several other physicochemical properties of the same electrolytes were studied to correlate to the concentration-dependent diffusion coefficients, including refractive index, viscosity, conductivity, and microstructure analysis based on vibrational spectroscopy (Infrared and Raman). High concentration electrolytes with more ion pairs show increased viscosity which ultimately leads to smaller diffusion coefficients. A QCM-I instrument standard flow cell were used to determine the viscosity of ZnSO4 electrolyte and the concentration-dependent viscosity was fitted to the function η=1.06-0.476m+2.13m2-1.01m3+0.204m4. Interionic interactions also led to reduced conductivity at concentrations beyond 1.5mol/kg, despite the increased charge density of concentrated solutions. FT-IR spectrums allowed analyzation of increased charge density, which increased intensity of the O-H stretching peak in concentrated electrolytes, despite the decrease in the ratio of water. Competition between charge density and viscosity continues to challenge the efficiency of concentrated electrolytes.Lastly, we demonstrate the prototype in situ triangular cell to characterize the electrolyte in working batteries. The cell responds to short, low-voltage pulses with beam deflection and relaxation, and offers an opportunity as a novel in situ spectroscopic tool to characterize the battery electrolyte. Acknowledgments This work is supported by a grant from NSF (CBET-2243098).

Calculation of liquidus in eutectic alkali halide mixtures using thermodynamic perturbation theory

A statistical-thermodynamic model that makes it possible to describe with good accuracy phase equilibria between melt and crystal in binary alkali halide mixtures with common cations and anions is proposed. This model is based on the thermodynamic perturbation theory, which takes into account the charge-dipole contribution to the interionic interaction of binary molten salts using a multicomponent mixture of charged hard spheres as a reference system. Specific expressions for chemical potentials, taking into account the charge-induced dipole interaction in the molten phase, are presented within the developed approach. Considering binary eutectic mixtures NaF–NaCl, CsF–CsCl, NaF–CsF, and NaCl–CsCl as an example, the liquidus curves obtained in two series of calculations are shown: with the equation of state and without it. The discrepancies between the calculated and experimental data on the position of eutectic equilibrium for most of the considered mixtures do not exceed about 10 percent on the temperature scale and 5 percent on the composition when using only the tabulated values of ionic radii and polarizabilities without any adjustment.

Effect of the external electric fields on the polarization and vibrational spectrum of 1-ethyl-3-methylimidazolium bis(trifluormethylsulfonyl)imide on graphene surface

Ionic liquids, emerging as innovative solvents for energy harvesting, necessitate a comprehensive understanding of their structural characteristics at the graphene-ionic liquid interface. This work delves into the effects of external electric fields (EEFs) on the polarization and vibrational spectrum of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim][NTf2]) on a graphene surface, employing density functional theory calculations. The analysis reveals that the geometrical configuration and stability of functional groups within the graphene-[Emim][NTf2] system are influenced by both the direction and intensity of the applied EEF. Notably, the threshold EEF strength required for dissociation varies based on the structural configuration of the anion. The electronic energy, dipole moment, and polarization rate under varying EEF conditions have been quantitatively assessed, providing insights into their EEF-dependent behaviors. Utilizing the independent gradient model approach, the inter-ion interactions, such as hydrogen bonding and van der Waals forces, under the influence of EEFs were analyzed, and how these interactions evolve with changes in the direction and intensity of the EEFs were also explored. Furthermore, the vibrational spectrum of [Emim][NTf2] on the graphene surface, spanning a range of 10–3500 cm−1, was meticulously calculated to systematically investigate the impact of the EEF on the vibrational spectra of the graphene-[Emim][NTf2] system. A key finding of this work is the distinct shifts in the vibrational peaks of the cis and trans isomers of [NTf2]− on the graphene surface, which can be attributed to differences in their exchange energies. Specifically, the exchange energy for the cis isomer of [NTf2]− is measured at 107.43 kJ∙mol−1, in contrast to 98.51 kJ∙mol−1 for the trans isomer.

Specificity of Interionic Interaction As a Factor in the Selective Extraction of “Soft” Anions from Aqueous Media Using 2(4)-Octylaminopyridines

Specificity of Interionic Interaction As a Factor in the Selective Extraction of “Soft” Anions from Aqueous Media Using 2(4)-Octylaminopyridines

C[sbnd]C bond cleavage in the electrooxidation of 2,3-butanediol controlled by an ionic liquid modifier

In heterogeneous catalysis, ionic liquids (ILs) are used as chemical modifiers to control selectivity. In our work, we aim to apply the same concept to electrocatalytic systems. As a model reaction, we studied the electrooxidation of 2,3-butanediol on the low-index Pt(111), Pt(100) and Pt(110) surfaces in an acidic environment. We used the IL 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([C2C1Im][OTf]) dissolved in an aqueous electrolyte as a catalyst modifier. The reaction mechanisms were investigated by electrochemical infrared reflection absorption spectroscopy (EC-IRRAS). The oxidation of 2,3-butanediol is highly structure dependent. On all three surfaces, the two products formed are acetoin and diacetyl, i.e. either one or two alcohol functionalities are oxidized. However, we observe distinct features on the different surfaces with respect to activity, potential window of oxidation, and selectivity. Only the Pt(100) surface is active towards CC bond cleavage. The latter reaction leads to the formation of COads and poisoning of the catalyst. Modification of this surface by addition of the IL leads to an increase of the selectivity for acetoin from 51 % to 78 % (at 1.1 VRHE). In addition, CC bond cleavage is suppressed, no CO is formed, and the surface remains active for the target reaction. We attribute these effects to the reversible and structure dependent adsorption of the [OTf]− anions on the Pt surfaces and additional interionic interactions. Our results demonstrate the potential of ILs to control selectivity in electrocatalytic reactions.

Plastic Crystal Fast Ion‐Conductor Electrolyte Enabled Ultra‐Low Temperature Rechargeable Organic Battery

AbstractBattery performance is much damaged by ultra‐low‐temperature (<−80 °C), due to the insufficient ionic conductivity and high desolvation energy barrier. The strong coupling between ion dissociation and ion‐desolvation much increases the difficulty in electrolyte‐design. Here, it is demonstrated that such issue can be fundamentally addressed by a salt‐led electrolyte engineering. The salt with poor interionic interaction can be easily dissociated under appropriate solvation force even at extremely low‐temperature. The new electrolyte‐design logic is validated by 1‐ethyl‐1‐methylpyrrolidinium bis(fluorosulfonyl)imide, an organic ionic plastic‐crystals (OIPCs)‐characteristic salt. With the mild solvation assistance from methyl acetate, the electrolyte supplies considerable conductivity of 0.36 mS cm−1 at −110 °C and enables the smooth charging/discharging of polyimide/polytriphenylamine all‐organic cell at ultra‐low‐temperature. Even with high material loading, the cell reserves 65% of theoretical capacity under 0.2 C‐rate at −110 °C. This work represents a significant advancement in the low‐temperature batteries, and provides new knowledge of the ionic dynamics of electrolyte.

Stretchable, self-adhesion and durable polyacrylamide/polyvinylalcohol dual-network hydrogel for flexible supercapacitor and wearable sensor

Conductive hydrogels show great promise in the field of flexible electronics, but traditional hydrogels have some problems such as poor environmental tolerance, being easy to damage and not being durable. In this work, polyacrylamide (PAM) was used as the main network, and polyvinylalcohol (PVA) was added to construct a dual network hydrogel. Simultaneously, LiTFSI was added to improve hydrogel ionic conductivity, and multiple interionic and intermolecular interactions formed within the gel, significantly improving the gel's mechanical properties and durability. The area specific capacitance of the hydrogel-based supercapacitor is 383.4 mF cm−2, and it still maintains a high cycle life of 90.35 % after 10,000 cycles. The hydrogel-based strain sensor shows fatigue resistance, rapid recovery after 400 stretches, high sensitivity (GF = 3.83 at 300–400 %), and the ability to detect human motion. Therefore, the multi-functional properties of PAM/PVA/LiTFSI hydrogels are expected to play a demonstration role in a new generation of flexible electronic products.

Tuning C-N Ullmann coupling with anion-exchanged ionic liquid-functionalized nanoparticle catalysts

Modern organic chemistry demands efficient and sustainable synthetic methods. Copper-catalyzed Ullmann coupling reactions, adept at constructing biaryl and aryl-heteroaryl motifs, have gained significant traction. However, traditional methods suffer from limitations. Nanoparticle catalysts, particularly copper nanoparticles (CuNPs), offer improved efficiency, but their performance is hampered by agglomeration and leaching. Hybrid supports incorporating ionic liquids (ILs) address this issue by providing a polar environment stabilizing CuNPs and enhancing catalytic activity and selectivity. This study investigates the impact of anion exchange in ionic liquids on the catalytic performance of C-N Ullmann couplings. Anion exchange modifies interionic interactions, hydrogen bonding, and dipolar properties, ultimately influencing the reaction's outcome. We synthesized CuNPs impregnated in silica supports functionalized with a triazolium-based ionic liquid possessing different anions (BF4−, PF6−, NTf2−) to elucidate the effect of anion exchange.Characterization techniques like FT-IR, XPS, TGA, and XPS confirmed successfully incorporating the triazole group and varying anions onto the material. TEM analysis showed the presence of CuNPs (4.5–5.7 nm) impregnated on the triazole functionalized silica supports.Catalytic studies yielded fascinating insights into the impact of different anions on conversion and selectivity. Iodide (I−) promoted higher conversion (100%), while tetrafluoroborate (BF4−) offered superior selectivity (57%). Computational studies provided valuable explanations, shedding light on the reactivity of the nanostructures and the interaction mechanism between substrates and the nanocatalyst. The theoretical results suggest that coordinative covalent bonds and highly polarized interactions govern the substrate interaction, with the aniline path achieving higher stabilization.Furthermore, the choice of anion influences the reactivity, substrate stabilization, and spin density distribution. These properties directly correlate with the conversion and selectivity observed in the catalytic studies.

UVC Up-Conversion and Vis-NIR Luminescence Examined in SrO-CaO-MgO-SiO2 Glasses Doped with Pr3.

The application of ultraviolet-C light in the field of surface treatment or photodynamic therapy is highly prospective. In this regard, the stable fluorescent silicate SrO-CaO-MgO-SiO2-Pr2O3 glasses able to effectively convert visible excitation on the ultraviolet praseodymium emission were fabricated and examined. An unusual wide-range visible-to-UVC up-conversion within 240-410 nm has been achieved in Pr3+-doped glasses, revealing their potential advantage in different sophisticated disinfection technologies. The integrated emission intensity was studied as a function of light excitation power to assess a mechanism attributed to UVC luminescence. Especially, it was revealed that the multicomponent silicate glass qualities and praseodymium 3PJ excited state peculiarities are favorable to obtaining useful broadband ultraviolet up-converted luminescence. The glass dispersion qualities were determined between 450-2300 nm. The impact of praseodymium concentration on Vis-NIR spectroscopic glass qualities was evaluated employing absorption spectra, emission spectra, and decay curves of luminescence associated with two involved praseodymium excited states. Especially, efficient interionic interactions can be inferred by investigating the decrease in 1D2 state experimental lifetime in the heavily doped samples. Examination of absorption spectra as a function of temperature implied that excitation at 445 nm should be quite effective up to T = 625 K. Contrary to this, temperature elevation gives rise to a moderate lowering of the visible praseodymium luminescence.

Regularities of Ion-Exchange Extraction of Anions 2(4)-Octylaminopyridines from Aqueous Media

Purpose of the study. Based on the results of the study of salts of 2(4)-octylaminopyridines (2(4)-OAP) by physical methods and their distribution in the two-phase system water-chloroform, establish the patterns of ion-exchange extraction of anions using aromatic amines.Methods. Chemical synthesis of 2(4)-OAP and their halides, spectrophotometry to determine the concentration of 2(4)-OAP in the aqueous and organic phase, characterization of 2(4)-OAP and their halides by IR, PMR and ESCA spectroscopy.Results. Synthesized by original methods and identified 2(4)-OAP and their halides. The distribution constants of 2-aminopyridine and 4-OAP salts with a singly charged anion in the water–chloroform two-phase system were determined. It is shown that the obtained constants increase in the following order: F-<Сl-<NO3-<Br-<ClO4-<SCN-<I-. In this case, a linear correlation between the logarithms of the constants and the hydration energy of anions in thisseries as a whole, which is typical for extraction with aliphatic amines and quaternary ammonium bases (FABs), is not observed. The results of the study of 2(4)-OAP halides by physical methods indicate a redistribution of the electron density in the aromatic cation depending on the nature of the anion, which ensures the selectivity of the extraction of “soft” (according to Pearson) 2(4)-OAP anions from aqueous media.Conclusion. The patterns of anion-exchange extraction of 2(4)-OAP, as well as, apparently, other aromatic amines, on the one hand, and aliphatic amines and PAO, on the other hand, coincide only with respect to “hard” anions. The situation changes during the extraction of "soft" anions. Due to the specificity of interionic interaction, aromatic amines are more selective with respect to "soft" anions, including, apparently, some acid complexes of "soft" metal cations, for example, with respect to halide complexes of platinum and other rare metals that are extracted by 2(4)-OAP better than by aliphatic amines and PAO.

Effects of pectin and temperature on the diffusion of ions and water in saltwater membranes

In this study, we investigate the structural and dynamical characteristics of the biopolymer pectin, exploring its impact on ion transport, diffusion activation energy, and relaxation timescales within a saltwater environment (100 mM NaCl (aq.)) using classical molecular dynamics (MD) simulations. Our analysis of radial distribution functions (g(r)) reveals a notable preference of Na+ ions to interact more extensively with pectin compared to Cl– ions. Moreover, we observe slight variations in the strength of inter-ion interactions, with a modest decrease in ion-pectin interaction strength with increased pectin loading. Additionally, our findings indicate that sodium exhibits the lowest diffusion coefficient due to the presence of significant energy barriers among Na+, Cl–, and water molecules, following the sequence: D(water) > D(Cl–) > D(Na+) at any pectin loading and temperature conditions within pectin-saltwater membranes. Furthermore, our study demonstrates that viscosity, ion-pair relaxation timescales and ion-cage relaxation timescales exhibit monotonic increases with pectin loading while displaying the opposite trend with temperature. Overall, our simulations strongly endorse the use of biopolymer pectin as a highly promising and innovative option for a wide range of industrial applications, including flexible hydrogel electrolytes and saline water treatment.

Performance of ionic liquid functionalized metal organic frameworks in the adsorption process of phenol derivatives.

The growth of industrial activities has produced a significant increase in the release of toxic organic pollutants (OPs) to the environment from industrial wastewater. On this premise, this study reports the use of metal organic frameworks (MOFs) impregnated with various ionic liquids (ILs) in the adsorption of phenol derivatives, i.e., 2,6-dimethylphenol and 4,4'-dihydroxybiphenyl. MOFs were prepared starting from 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) with divalent (Co, Ni, Cu) and trivalent (Ce) metal salts in mild hydrothermal conditions using water as a green solvent. Imidazolium base ionic liquids, namely 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium nitrate, 1-butyl-3-methylimidazolium chloride, and 1-hexyl-3-methyl-imidazolium chloride, were used to modify MOFs, leading to composite materials (IL@MOF), which show the structural characteristics of MOFs, and complement the advantages of ILs. SEM, EDX images, and TG data indicate that the IL is just attached on the surface of the adsorbent material, with no changes in crystal size or morphology, but with slightly altered thermal stabilities of IL@MOF composites compared to the original ILs and MOFs, pointing to some interionic interaction between IL and MOF. This research consists of equilibrium experiments, studying the effect of the initial concentration of OPs on the adsorption efficiency of the as-prepared MOFs and IL@MOF, in order to determine the influence of the nature of the adsorbent on its developed adsorption capacity and to investigate the performance of both ILs and MOFs. To determine the maximum adsorption capacity, several empirical isotherms were used: Langmuir, Freundlich, Redlich-Peterson, and Dubinin-Radushkevich. The characteristic parameters for each isotherm and the correlation coefficient (R2) were identified. The IL modification of MOFs increased the adsorption capacity of IL@MOF for the removal of phenol derivatives from aqueous solution. The adsorption capacity function of the MOF structure follows the trend CeHEDP > CoHEDP > NiHEDP > CuHEDP. The best performance was achieved by adsorbent materials based on Ce.

Quantifying neptunium oxidation states in nitric acid through spectroelectrochemistry and chemometrics

Controlled-potential in situ thin-layer spectropotentiometry was leveraged to generate visible/near-infrared (VIS/NIR) absorption spectral data sets for the development of chemometric models to quantify Np(III/IV/V/VI) oxidation states in HNO3. This technology would be valuable in laboratory studies and when monitoring process solutions to guide feed adjustments for radiochemical separations—the performance of which depends on oxidation state. This approach successfully isolated and stabilized Np species in pure (∼99%) oxidation states without compromising solution optical properties. Multivariate curve resolution–alternating least squares models were evaluated to resolve spectral and component concentrations from a scan that sequentially produced Np(VI), Np(V), Np(IV), and Np(III) spectra with mixtures of two valences at a time. Although it provided a useful approximation, the method was not able to quantitively resolve each component likely because of rotational ambiguity. Additionally, partial least squares regression models were built from artificial and electrochemically generated VIS/NIR spectral training sets to study the effect of interionic interactions on spectral characteristics. Models built with true Bi-chemical mixtures of coexisting Np oxidation states and spectra generated from additive combinations of pure end points had similar prediction performance. This methodology can be used to directly quantify Np concentration and the ratio of Np oxidation states and other actinides in remote settings such as hot cells.

Effect of anion and methylation on the interionic interactions and reactivity of 1-butyl-2,3-dimethyl imidazolium-based ionic liquids

The study presents the investigation of anion and methylation effects on the interionic interactions, thus explaining the variations in the reactivity, electronic, and spectroscopic features in 1-butyl-2,3-dimethyl imidazolium-based ionic liquids with chloride, tetrafluoroborate, and hexafluorophosphate anions. Ground state electronic structures, IR and Raman spectra, electronic transition characteristics, and chemical shifts of the ionic liquids were obtained using DFT calculations at the B3LYP/6–311++G(d,p) level of theory. The calculated electron densities were analyzed to determine intra- and interionic interactions at critical points using Reduced Density Gradient and topological analysis through the atoms-in-molecules approach. Experimental spectroscopic characterizations were performed using the FT-IR, FT-Raman, NMR, and UV–vis techniques. These techniques and DFT calculations provide essential contributions to interpreting spectral features concerning the structure and dynamics of ionic liquids. Furthermore, molecular docking studies were performed to determine the binding status of studied ionic liquids with human serum albumin to explore their activity, thus reporting their potential due to their demand in pharmacology.

Weakness of ionic bonds and solid decomposition in calcium phosphides under high pressure

In this work, we have investigated the structures and phase transitions of the Ca-P system under high pressure using the first-principles calculation method combined with the CALYPSO structural searching technique. We discovered new phases with the chemometrics of CaxPy (x/y = 1/1, 1/2, 3/2,2/1) and found that Ca3P2 and Ca2P decompose into elemental solid calcium and phosphorus at external pressures of 459 GPa and 478 GPa, respectively. This phenomenon contradicts the common knowledge that pressure usually leads to denser and more stable compound structures. As pressure increases, the ΔPV term of the compound exhibits an upward trend, which serves as the principal cause of Ca3P2 decomposition. We have delved into the electronic properties of Ca3P2, encompassing Bader charge, Madelung energy, band structures, Electron Localization Function (ELF), and ICOHP. The findings give evidence that the abatement of inter-ionic interaction, triggered by pressure, constitutes the foremost factor inducing Ca-P compounds composition into solid elements. Our research elucidates how high pressure regulates Ca-P compounds behavior and electronic properties, and offers valuable insight into the behavioral transformations of other alkaline-earth metal phosphides under high pressure.

External field intensity and wavelength dependency from IR to deep UV of linear and nonlinear optical properties of 1-butyl-3-methylimidazolium dicyanamide ionic liquid

The electronic structure, inter-ionic interactions and charge transfer, polarizability, and first-order and second-order hyperpolarizabilities of 1-butyl-3-methylimidazolium dicyanamide ionic liquid have been explored via modeling at M06-2X/6-311++G(d,p) level of theory. External field intensity dependence of electronic properties was investigated by utilization of field intensity from 0.0001 to 0.002 au applied in the direction of anion-cation. Interionic interactions have been characterized through the reduced density gradient method to reveal and distinguish hydrogen bonding and other non-covalent interactions. Extraordinary bonding interactions were observed between the anion and ring system of the cation. Electronic excitation characteristics were analyzed based on the inter-fragment charge transfer method to distinguish charge transfer contributions from local excitations. Static and dynamic nonlinear optical parameters namely the total dipole moment μ, the mean polarizability α(0,0) and α(−ω; ω), the anisotropy of polarizability Δα(0,0) and Δα(−ω; ω) the first hyperpolarizability in the direction of dipole moment β(0,0,0), β(−ω; ω,0), and β (−2ω; ω,ω), the average second hyperpolarizability γ(0;0,0,0), γ(−ω; ω,0,0) and γ(−2ω; ω,ω,0) have been calculated for specific laser wavelengths corresponding to the UV, visible, and infrared region. Thus, a novel way of mapping the field intensity and wavelength dependence of NLO properties was achieved. The hyperpolarizability calculations indicate that 1-butyl-3-methylimidazolium dicyanamide has a significant potential to be used in electro-optics Pockels effect, second-harmonic generation, and electro-optical Kerr effect applications. NLO property maps indicate that the wavelength dependence in the IR and visible region is almost ignorable when compared with that of the UV region where the first hyperpolarizabilities can increase by ten thousand and the second hyperpolarizabilities can reach up to ten billion times.

Carbonates of alkaline earth metals: Impact of the cation size on strengths of interionic interactions and polymorphic preferences

The energies of all types of pair-wise interionic interactions between atoms of the representative (MCO3)13 clusters sampled from X-ray structures of rhombohedral magnesite (M = Mg) and calcite (M = Ca), on one hand, and orthorhombic aragonite (M = Ca) and cerussite (M = Pb), on the other hand, are evaluated theoretically to ascertain how the size of a divalent metal cation governs the preferable existence of rhombohedral or (and) orthorhombic polymorph (polymorphs) at ambient temperature and pressure. The carbonates studied and their clusters are considered as those consisting of (i) columns of carbonate anions (CAs) separated by trios of cations, (ii) ribbons and layers of CAs, and (iii) rods and layers of cations. For each cluster, coordination energies of six CAs by a cation and six cations by a CA are evaluated. Energies of interactions of C and O atoms of columns and ribbons with cations and energies of inter-anionic C···O, O···O, and C···C interactions in column and ribbons of clusters are compared. Strengths of cation – cation repulsions are also evaluated. Analyses of the interaction energies, interionic distances in the carbonates studied, and thermodynamic properties of carbonates of alkaline earth metals allow one to understand how the size of a particular divalent metal cation affects relative thermodynamic stabilities and the very existence of its rhombohedral or (and) orthorhombic crystalline phase (phases).

Synthesis and solid state structures of 1,3-dihalo-1,3-bis(dialkylamino)propenium salts and related compounds

1,3-dicholoro-1,3- bis(dialkylamino)propenium salts are prepared by condensing N, N,-dialkylamides with dichloromethylene dimethyliminium chloride (“Viehe's salt”). The products are versatile synthons and can be used to make a variety of ligand types. Here, we report the syntheses of a number of new propenium salts and provide comprehensive characterization data for some that have already been described. Additionally, we have prepared a series of related 1,3-dihalo-1,3- bis(dimethylamino)propenium salts via halogen exchange reactions (F through I). Finally, all of the compounds described, including Viehe's Salt and several hydrolysis products, have been characterized in the solid state using single crystal X-ray diffraction. The symmetrical cations [Me2NC(X)CHC(X)NMe2]+ were found to take one of two general structural forms. The first (X = H or F) is planar, presumably maximizing the delocalization within the backbone of the cation, while the second form is markedly twisted (X = Cl, Br or I). Calculations indicate that the latter develop increasingly positive regions of the electrostatic potential on the halide substituents, allowing cation/anion interactions via halogen bonding to dominate in the extended solids. The results of these studies illustrate the importance of the differing interionic interactions in a homologous series of small organic salts.