Molecular Salt Research Articles

Synthesis and crystal structure of (E)-2-({2-[aza-niumyl-idene(methyl-sulfan-yl)meth-yl]hydrazinyl-idene}meth-yl)benzene-1,4-diol hydrogen sulfate.

The title mol-ecular salt, C9H12N3O2S+·HSO4 -, was obtained through the protonation of the azomethine N atom in a sulfuric acid medium. The crystal com-prises two entities, a thio-semicarbazide cation and a hydrogen sulfate anion. The cation is essentially planar and is further stabilized by a strong intra-molecular O-H⋯N hydrogen bond. In the crystal, a three-dimensional network is established through O-H⋯O and N-H⋯O hydrogen bonds. A weak intermolecular C-H⋯O hydrogen bond is also observed. The hydrogen sulfate anion exhibits disorder over two sets of sites and was modelled with refined occupancies of 0.501 (6) and 0.499 (6).

1-Isobutyl-8,9-dimethoxy-3-phenyl-5,6-dihidroimidazo[5,1-a]isoquinolin-2-ium chloride

The molecular salt, C23H26N2O2 +·Cl−, was obtained from 1-isobutyl-8,9-dimethoxy-3-phenyl-5,6-dihydroimidazo[5,1-a]isoquinoline, which was synthesized by cyclocondensation of α-benzoylamino-γ-methyl-N-[2-(3,4-dimethoxyphenyl)ethyl]valeramide in the presence of phosphoryl chloride. The tetrahydropyridine ring adopts a twist–boat conformation. In the crystal structure, centrosymmetric dimers are formed by N—H...Cl and C—H...Cl hydrogen bonds.

Tetra-n-butyl-ammonium orotate monohydrate: knowledge-based comparison of the results of accurate and lower-resolution analyses and a non-routine disorder refinement.

The title hydrated mol-ecular salt (systematic name: tetra-n-butyl-ammonium 2,6-dioxo-1,2,3,6-tetra-hydro-pyrimidine-4-carboxyl-ate monohydrate), C16H36N+·C5H3N2O4 -·H2O, crystallizes with N-H⋯O and O-H⋯O hydrogen-bonded double-stranded anti-parallel ribbons consisting of the hydro-philic orotate monoanions and water mol-ecules, separated by the bulky hydro-phobic cations. The hydro-phobic and hydro-philic regions of the structure are joined by weaker non-classical C-H⋯O hydrogen bonds. An accurate structure analysis conducted at T = 100 K is compared to a lower-resolution less accurate determination using data measured at T = 295 K. The results of both analyses are evaluated using a knowledge-based approach, and it is found that the less accurate room-temperature structure analysis provides geometric data that are similar to those derived from the accurate low-temperature analysis, with both sets of results consistent with previously analyzed structures. A minor disorder of one methyl group in the cation at low temperature was found to be slightly more complex at room temperature; while still involving a minor fraction of the structure, the disorder at room temperature was found to require a non-routine treatment, which is described in detail.

Crystal structure, Hirshfeld surface analysis and physicochemical characterization of bis-[4-(di-methyl-amino)-pyridinium] di-μ-chlorido-bis[di-chlorido-mercurate(II)

The title mol-ecular salt, (C7H11N2)2[Hg2Cl6], crystallizes with two 4-(di-methyl-amino)-pyridinium cations (A and B) and two half hexa-chlorido-dimercurate(II) anions in the asymmetric unit. The organic cations exhibit essentially the same features with an almost planar pyridyl ring (r.m.s. deviations of 0.0028 and 0.0109 Å), which forms an inclined dihedral angle with the dimethyamino group [3.06 (1) and 1.61 (1)°, respectively]. The di-methyl-amino groups in the two cations are planar, and the C-N bond lengths are shorter than that in 4-(di-methyl-amino)-pyridine. In the crystal, mixed cation-anion layers lying parallel to the (010) plane are formed through N-H⋯Cl hydrogen bonds and adjacent layers are linked by C-H⋯Cl hydrogen bonds, forming a three-dimensional network. The analyses of the calculated Hirshfeld surfaces confirm the relevance of the above inter-molecular inter-actions, but also serve to further differentiate the weaker inter-molecular inter-actions formed by the organic cations and inorganic anions, such as π-π and Cl⋯Cl inter-actions. The powder XRD data confirms the phase purity of the crystalline sample. Furthermore, the vibrational absorption bands were identified by IR spectroscopy and the optical properties were studied by using optical UV-visible absorption spectroscopy.

Molecular salts of terephthalic acids with 2-aminopyridine and 2-aminothiazole derivatives as potential antioxidant agents; Base-Acid-Base type architectures

Molecular salts of terephthalic acid (TA) with 2-amino-4-chloropyridine (ACP), 2-amino-6-methylpyridine (AMP), 2-aminothiazole (AT) and 2-amino-5-methylthiazole (AMT), were prepared with an intent to get new crystalline materials with improved physical properties. Crystals of the desired compounds were obtained through slow evaporation technique. The solid state structures reveal that proton transfer from acid to aromatic nitrogen of the base occurs, thus affording molecular salts of general representation AT-TA-AT (1), AMT-TA-AMT (2), AMP-TA-AMP (3) and ACP-TA-ACP (4). The NH2 group at position 2 of each amino base is still available to interact with CO to afford planar fragment. The COOH functional groups in TA at para position with respect to each other accommodated the respective base in a 1:2 M ratio (acid:base, respectively) to give almost planar Base-Acid-Base (BAB) fragments. The resultant molecular salts were structurally characterized with the help of FT-IR and X-ray diffraction. The antimicrobial (selected strains), antioxidant (2,2-DiPheny-1-Picry-l-Hydrazyl, DPPH and 2,2′-Azino-Bis(3-ethylbenzoThiazoline-6-Sulphonic acid, ABTS) and enzyme inhibition (AChE, BChE and AGS) potencies of the synthesized Base-Acid-Base type, molecular salts were explored. In addition to improved physical properties, all molecular salts showed promising biological activities.The optimization, natural bonding orbitals (NBOs) and FT-IR analysis of the molecular salts were carried out by DFT/B3LYP/6-311G (d,p) level in PCM model with ethanol solvent. However, frontier molecular orbitals (FMOs) analysis was performed utilizing TD-DFT/B3LYP/6-311G (d,p) level. A comparative analysis reveals that consistency is found between the experimental and theoretical findings of geometric parameters and vibrational frequencies. The inter-molecular hydrogen bond (IHB) and hyper conjugative interactions are characterized by NBO analysis. The chemical stability of molecules is evaluated by FMOs. The energies of FMOs are also used to calculate the global reactivity descriptor parameters. The obtained high softness values indicated that entitled compounds might be biologically active.

Crystal structure and Hirshfeld surface analysis of bis-[hydrazinium(1+)] hexa-fluorido-silicate: (N2H5)2SiF6.

In the title inorganic mol-ecular salt, (N2H5)2SiF6, the silicon atom at the centre of the slightly distorted SiF6 octa-hedron [range of Si-F distances = 1.6777 (4)-1.7101 (4) Å] lies on a crystallographic inversion centre. In the crystal, the ions are connected by N-H⋯N and N-H⋯F hydrogen bonds; the former link the cations into [010] chains and the latter (some of which are bifurcated or trifurcated) link the ions into a three-dimensional network. The two-dimensional fingerprint plots show that F⋯H/H⋯F inter-actions dominate the Hirshfeld surface (75.5%) followed by H⋯H (13.6%) and N⋯H/H⋯N (8.4%) whereas F⋯F (1.9%) and F⋯N/N⋯F (0.6%) have negligible percentages. The title compound is isostructural with its germanium-containing analogue.

Response Surface Methodology for the Evaluation of Magnetite Partitioning Behavior in Polyethylene Glycol-Based Aqueous Biphasic System

Response surface methodology in the framework of central composite design has successfully applied to polyethylene glycol (PEG)-based aqueous two-phase system in order to evaluate its efficiency in extracting Fe from iron ores with respect to PEG molecular weight, PEG concentration and salt concentration factors. Furthermore, ANOVA and multiple regression analysis have provided a second-order polynomial equation that is highly capable of predicting the experimental results. The PEG molecular weight and weight percent of the salt in the feed had a major and minor effects on the iron ion partition coefficient, respectively.

N,N,N-Trimethyl-1-[4-(pyridin-2-yl)phenyl]methanaminium hexafluoridophosphate

In the cation of the title molecular salt, C15H19N2 +·PF6 −, the dihedral angle between the benzene and pyridine rings is 38.21 (10)°. In the crystal, weak C—H...F interactions arising from methyl and methylene groups adjacent to the quaternary N atom generate (001) sheets.

Terahertz generation and optical characteristics of P-BI.

We present the structural and THz generation characteristics of the molecular salt crystal (E)-2-(4-(dimethylamino)styryl)-1,1,3-trimethyl-1H-benzo[e]indol-3-ium iodide (P-BI) using optical rectification with IR pump wavelengths. P-BI shows a peak-to-peak field ∼6 times greater than inorganic crystal GaP, and a broader THz spectrum. Data were obtained from 0-6THz showing a significant dip in generation at 1.8THz, similar to what has been observed with the THz generation crystal DAST at 1THz. We characterized the power dependence of P-BI at different IR wavelengths, with optimal THz generation at the 1550-nm pump wavelength. To model THz generation as a function of P-BI crystal thickness, we measured the THz complex refractive index and the IR group index; modeling shows that imperfect phase matching leads to spectral narrowing centered at ∼2.5 THz as the crystal thickness is increased. P-BI could provide a useful alternative to inorganic THz generation crystals such a GaP.

Polymorphic Forms of a Molecular Salt of Phenazopyridine with 3,5-Dihydroxybenzoic Acid: Crystal Structures, Theoretical Calculations, Thermodynamic Stability, and Solubility Aspects

The polymorphism of multicomponent crystals has not been studied as widely as that of single-component crystals. In this work, two polymorphic forms of a pharmaceutical salt of phenazopyridine with...

Enhancing the permeability of TFC membranes based on incorporating polyamide matrix into MWCNTs framework

Reverse osmosis (RO) technology can get rid of small molecular contaminants and salts with a very high efficiency, so that it has exhibited promising potential for addressing the emerging problem of a clean water shortage. In this paper, one new thin film composite (TFC) membrane with a novel MWCNT/polyamide (MWCNT/PA) composite rejection layer had been manufactured via interfacial polymerization (IP) method under negative pressure. The MWCNTs framework was first fabricated on surface of PVDF substrate and then the polyamide matrix was filled into the framework by IP process between the two monomers (M-phenylenediamine and trimesoyl chloride) under negative pressure. The novel rejection layer obviously enhanced the water flux and antifouling performance without harming the desalination rate in RO process. The improved performances can be attributed to the larger amount of hydrophilic MWCNTs which were embedded into the rejection layer and worked as water channels. Meanwhile, this research also revealed that enhancing the density of water channels in polyamide rejection layer and the hydrophilicity of membrane surface could effectively improve the TFC membrane performance.

Polymer phase transition characteristics coupled with GC-MS for the determination of phthalate esters.

Phthalate esters are easily released from plastics materials and migrate into the soil and water environment, causing serious pollution and posing a great threat to the health of human beings. A novel temperature-sensitive extractant combined with liquid-liquid microextraction was developed to preconcentrate three phthalates in the water environment. To optimize the extraction efficiency for the three phthalate esters, various parameters, including polymer molecular weight, salt type, salt addition, adsorption time, desorption solvent, desorption volume, and desorption time have been studied. Under optimal conditions, limits of detection and limits of quantification were in the range of 0.007-0.120and 0.021-0.350µg/L, respectively. Linearities varied in the range of 5-1000 µg/L, with the correlation coefficients of 0.9867-0.9997. The preconcentration factors were in the range of 25-75. The relative recoveries of the three phthalate esters were in the range of 82.2-105.6% at the spiked levels. The relative standard deviations were in the range of 0.7-9.2% based on triplicate measurements. The results indicate that the temperature-sensitive material is a good extractant for phthalate esters in water samples.

High‐throughput screening of aqueous biphasic systems with ionic liquids as additives for extraction and purification of enveloped virus‐like particles

Due to their unique properties, virus‐like particles (VLPs) have been portrayed as a promising high‐value biopharmaceutical in VLP‐based vaccination and cancer therapy. Nevertheless, due to limited physical and economical capabilities of the current downstream processing of VLPs, their production is still difficult and seen as a major problem that needs to be tackled. In this work, high‐throughput screening on a liquid handling station (LHS) has been implemented for efficient selection of adequate polymer‐salt aqueous biphasic systems (ABS) for extraction and purification of enveloped Hepatitis C virus pseudoparticles (HCVpp). The effect of polyethylene glycol (PEG) molecular weight and salt type (citrate, sulfate, and phosphate) was first evaluated. Furthermore, to optimize extraction parameters, the effect of pH and tie‐line lengths (TLL) was also addressed. For the most promising ABS and extraction conditions, the addition of ten ionic liquids (ILs) as adjuvants was investigated. Insights on the chemical features of ILs that impact HCV‐VLPs partitioning are highlighted. Finally, the potential of studied ABS containing ILs as adjuvants in the extraction and purification of VLPs from cell culture supernatants was addressed. The 100% extraction efficiency of VLPs in the PEG‐rich phase was achieved, and VLP purity was increased compared to the system without IL. In conclusion, these promising results show that ILs can be very effective in modulating the phase properties of polymer‐salt ABS, achieving high HCV‐VLP purification.

Influence of Host Polarity on Correlating Salt Concentration, Molecular Weight, and Molar Conductivity in Polymer Electrolytes.

We use coarse-grained molecular dynamics simulations to study the effect of salt concentration and host polymer molecular weight on ion transport in polymer electrolytes. We find that increasing salt concentration or molecular weight similarly slows polymer dynamics across a wide range of host polarities, and that the resulting relaxation times display a correlation to the product of the salt concentration and polymer molecular weight. However, we find that molar conductivity only decreases with polymer dynamics at high polarities but is uncorrelated with the latter at low polarities. We attribute such differences to the variation in ionic aggregation between high and low polarity electrolytes. At low polarity, ionic dissociation significantly increases with molecular weight and salt concentration, offsetting the slowdown in polymer dynamics and yielding the observed insensitivity of molar conductivity. However, at high polarity, ions are mostly dissociated, independent of either molecular weight or salt concentration, thereby strongly coupling molar conductivity to polymer dynamics.

Hydrophobic SiO2 nanoparticle‐induced polyvinylidene fluoride crystal phase inversion to enhance permeability of thin film composite membrane

ABSTRACTThin film composite (TFC) membrane can get rid of small molecular contaminants and salts with a very high efficiency, thus exhibiting promising potential for addressing the emerging problem of a clean water shortage. In this work, a new type of TFC membrane was prepared by interfacial polymerization of two monomers (MPD and TMC) on surface of SiO2/polyvinylidene fluoride (PVDF) substrate. The maximum flux of 3.16 L m−2 h−1 Bar−1 was achieved for the optimized hydrophobic SiO2 nanoparticles well dispersed in PVDF substrate, which is 2.6 times higher than that of 1.21 L m−2 h−1 Bar−1 for the commercial cellulose triacetate reverse osmosis membrane. The improved performance of TFC membrane could be attributed to the higher compaction resistance of SiO2/PVDF substrate. Further analysis revealed that PVDF crystal phase inversion induced by superhydrophobic SiO2 nanoparticles obviously enhanced the intramolecular and intermolecular hydrogen bonds between PVDF polymer molecules. Additionally, the narrower finger‐like pore size and thicker pore wall of SiO2/PVDF substrate also played significant roles in enhancing the compaction resistance of PVDF membrane. This work also provides a proof‐of‐concept demonstration of high permeability substrates for effective flux enhancement of TFC membranes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48204.

Enhancement of emission from indium in flowing liquid anode atmospheric pressure glow discharge using organic media

The effect of addition of low molecular weight organic compounds, i.e. acids, salts and alcohols, on the emission measured from In with flowing liquid anode atmospheric pressure glow discharge optical emission spectrometry (FLA-APGD-OES) was studied. It was revealed that a small addition of CH3OH or C2H5OH (0.5%, v/v) enhanced the intensity of In 451.1 nm atomic line over 30-times. The observed boosting of emission was caused both not only by promotion of the analyte transport efficiency from the liquid sample to the plasma phase (increased from 19% to 35%) but also due to some other factors, presumably the improvement of atomization/excitation conditions. The developed FLA-APGD-OES method offered a very low detection limit of In which was 0.21 μg L−1 (using a miniaturized spectrometer) or even 0.030 μg L−1 (using a high-resolution spectrometer). Furthermore, it was demonstrated that addition of alcohols significantly reduced the matrix effects from several interfering species, e.g. Ag, Cu, Pb and Zn, and only in case of Na, the anti-interference effect was observed. The intensity improvement which resulted from the addition of alcohols, was observed for In only and it did not occur for other elements such as Ag, Cd, Hg, Pb, Tl and Zn.

Exploration of the Luminescence Properties of Organic Phosphate Salts of 3‐Quinoline‐ and 5‐Isoquinolineboronic Acid

3‐Quinoline‐ and 5‐isoquinolineboronic acids (3QBA and 5IQBA) were combined with 1‐naphthyl and diphenyl phosphate (1NP and DPP) to give three crystalline molecular salts of 1:1 stoichiometric composition, viz., 3QBA‐1NP, 5IQBA‐1NP and 3QBA‐DPP. The products were characterized by elemental analysis, single‐crystal X‐ray diffraction studies, IR spectroscopy, luminescence spectroscopy and TG‐DSC measurements. The analysis of the solid‐state structures revealed that the molecular components are linked by strong charge‐assisted hydrogen bonds forming heterodimeric synthons of the type B(OH)2···–O2P and N+–H···O(P). In addition, the hydrogen phosphate salts derived from 1NP exhibit the homodimeric P(O)OH···O(HO)P synthon. The aggregates formed through the above‐mentioned hydrogen bonding motifs are further connected through π···π interactions, which involve mainly the aromatic rings of the quinolinium/isoquinolinium cations. The crystal structure analyses were accomplished by Hirshfeld surface analyses and the associated 2D fingerprint plots, illustrating the similarities and differences of the three salts more concisely. Solid‐state photoluminescence spectroscopy of the title compounds showed emission in the blue region with an extraordinary high quantum yield (Φf = 98 %) for compound 3QBA‐DPP.

Supramolecular networks and Hirshfeld surfaces of oxydiacetic acid and iminodiacetic acid salts.

Oxydiacetic acid (Oda) and iminodiacetic acid (Ida) have been combined with two diamines, namely ethylenediamine (en) and o-phenylenediamine (o-phen), to give three molecular crystals of compositions [(Oda2-)(en2+)]·H2O (Odaen), [(Ida-)(0.5en+)] (Idaen) and [(Oda-)(o-phen+)] (Odaophen). Single crystal X-ray structure determination of the three molecular salts revealed that the hydrogen bonding interactions form distinct supramolecular chains. In Odaen, water molecules and Oda2- anions generate one-dimensional supramolecular chains where two chains overlap each other in zigzag form. In Odaophen, Oda- anions generate a one-dimensional linear supramolecular chain. In Idaen, both intermolecular and intramolecular proton transfer occurs. Ida- anions generate a one-dimensional zigzag chain. These one-dimensional supramolecular chains extend to form different two-dimensional supramolecular chains by the interaction of diaminium and monoaminium cations. Intermolecular close contacts are also examined using Hirshfeld analysis to reveal similarities and differences in the crystal structures.

Synthesis, growth, structural characterization and biological investigation of hydrogen bonded organic molecular salt: N, N-diethylanilinium-5-sulphosalicylate

N, N-diethylanilinium-5-sulphosalicylate was successfully synthesized and good optical quality single crystals were grown employing slow solvent evaporation solution growth technique at ambient temperature. The CHN analysis indicates that the titled crystal is composed of stoichiometric proportion of the constituent ions, free from impurities and devoid of water molecules. The UV–Visible absorption spectrum exhibits the bands due to π-π* and n- π* transitions occurring in the salt. FT-IR spectral studies were performed to identify the different vibrational modes present in the titled crystal. The formation of salt and the molecular structure were initially confirmed by 1H and 13C NMR spectroscopic Studies. Single crystal XRD analysis indicates that the titled crystal belongs to monoclinic crystal system with centrosymmetric space group, P21/c. The hydrogen bonding parameter reveals that the salt crystal possesses N–H⋯O, O–H⋯O and C–H⋯O types of hydrogen bonding which are responsible for the stabilization of the crystal structure. TG/DTA Analyses reveal that the crystal is thermally stable up to 270 °C. The Vickers microhardness study reveals the soft nature of the titled crystal. Further, the titled salt was screened for its antimicrobial and antioxidant activities. The antimicrobial studies reveal that the synthesized salt has significant antibacterial and antifungal activities comparable to the standard compounds. The antioxidant activities of the titled salt show that the synthesized salt exhibits moderate activity against DPPH radical.

Cationic electrolyte copolymers of diallyldimethylammonium chloride with carboxybetaine 2-(diallyl(methyl) ammonio) acetate of various compositions in water solutions of different ionic strengths

Random copolymers of diallyldimethylammonium chloride (DADMAC) and carboxybetaine 2-(diallyl(methyl)ammonio) acetate (DAMA) with different compositions (10%/90%), (50%/50%) and (70%/30%), as well as poly(DAMA) and poly(DADMAC) homopolymers, were synthesized. Molecular characteristics of poly(DADMAC–co–DAMA) copolymers and homopolymers were determined in water solutions in the presence of 0.1 M NaOH and a low molecular weight salt (NaCl in various concentrations) by viscometery, dynamic and static light scattering. Dependences of several important conformational parameters, such as swelling coefficient α, the Huggins constant kH, and the second virial coefficient A2, on copolymer composition (charge asymmetry) and NaCl concentration in solution were analyzed. It was shown that growth of charge asymmetry leads to sharp increase in copolymer size.