Series Of Salts Research Articles

Synthesis and Investigation of 2,4,6‐Trinitropyridin‐3‐ol and its Salts

AbstractA series of novel energetic salts of 2,4,6‐trinitropyridin‐3‐ol have been prepared and confirmed structurally. These compounds can be prepared by means of a facile synthetic procedure and show outstanding properties (detonation velocity, detonation pressure, sensitivity toward mechanical stimuli, and temperature of decomposition). They were isolated and characterized by means of elemental analysis, multinuclear (1H, 13C) NMR spectroscopy. The structures in the crystalline state were determined by single‐crystal X‐ray diffraction at 296 K. From the calculated standard molar enthalpy of formation (CBS‐4 M) and the densities, the Chapman‐Jouguet detonation properties were predicted by using the EXPLO5 V6.02 thermochemical computer code. Their sensitivities towards impact and friction were also determined.

Salt-tolerance of alkyl-glyceryl ether carboxylates hydrotropes and surfactants. Dramatic effect of the methylation of the glyceryl spacer

HypothesisThe insertion of polyether spacers between the anionic head and the alkyl chain of ionic surfactants significantly improves their salt-tolerance. The aim of this work is to study whether the petro-based polyethoxy spacer can be replaced by a glyceryl ether group for high salinity applications. ExperimentsA series of amphiphilic sodium salts of alkyl glyceryl ether carboxylates are synthesized with different alkyl chain lengths from 4 to 12 and various spacers between the glyceryl and the carboxylate groups. Their aggregation behavior is studied by tensiometry and their amphiphilicities are assessed by the PIT-slope method. The dramatic effect of the methylation of the glyceryl spacer on the salt-tolerance is highlighted, and rationalized by DFT calculations and molecular dynamics. FindingsIn contrast to the corresponding sodium soap, n-C6H13-CO2Na, and to the non-methylated counterpart, the sodium salt of 1-pentyl-3-methyl glyceryl ether methylene carboxylate ([5.0.1]-CH2CO2Na) exhibits an excellent salt-tolerance since it remains water-soluble with NaCl or CaCl2 concentrations greater than 20 wt% at 25 °C. Amphiphiles with short alkyl chains (<C8) act as hydrotropes whereas longer compounds behave as surfactants whose CMC are lower than their corresponding isomers with ethoxy spacers n-Ci(EO)2CH2CO2Na.

Design, synthesis, and application of a new series of organogelator using crystal engineering approach and solvent parameter study: A synergetic approach

A new series of organic salts (A1B1-A1B6) based on pivalic acid and primary amine (alicyclic, aromatic, aliphatic) has been designed and synthesized for its potential organogelation behavior. A simple strategy of synthesizing 1-D hydrogen bonded network of PAM (primary ammonium monocarboxylate) leads to the discovery of five new gelators. All the synthesized salts (gelator/non-gelator) were subjected to single crystal X-ray studies to support the hypothesis that 1-D hydrogen bonded networks favor gelation. A detailed study of solvent parameters like dielectric constants, Kamlet-Taft parameters, Hansen parameters, etc. was carried out to get an insight into the role of solvents on the thermal stability and gelation performance of these salts. Organogelation behavior of Salts (A1B1-A1B5) is found to be dependent upon bulk solvent properties such as dielectric constant (ε), polarity index (P′) and a strong correlation between multi-component solvent parameters such as (β) and polar cohesive energy (δp) is observed. Gel network of salt A1B3 (in Acetonitrile solvent) has been used as a template for synthesis of silver nano particles owing to its rectangular hollow xerogel fibers.

Modulation of the binding affinity of naproxen to bovine serum albumin by conversion of the drug into amino acid ester salts

Naproxen (NAP) is one of the most widely prescribed non-steroidal anti-inflammatory drugs. Novel formulations of NAP aiming at better water-solubility, dosage, and the onset of action or new routes of application in order to minimize or prevent side effects of NAP are in the current interest of the pharmaceutical industry. Here, we report the synthesis, chemical, spectral and physicochemical characterization of a series of salts containing cations amino acid alkyl esters (AAE) and NAP anion, which potentially can be used as novel drug formulation. The [l-AAE][NAP] were obtained in three steps: preparation of the AAE hydrochlorides, neutralization of the hydrochlorides to the corresponding AAE, and formation of the target organic salts. All NAP derivatives, tested at a concentration as high as 100 μM, exhibited no toxicity against murine macrophage cell line (RAW 264.7). The binding parameters and stoichiometry of [AAE][NAP]s to bovine serum albumin (BSA) are in the range of that estimated for the parent NAP. Only l-valine isopropyl ester naproxenate characterizes with about one order of magnitude lower binding affinity for BSA, which suggests a faster diffusion rate in the circulatory system than the parent NAP and other derivatives, and therefore faster reach to the target system. Using molecular modeling seven binding pockets of BSA were probed for their suitability to binds the cation and the anion and results are discussed in correlation with the obtained thermodynamic parameters for the binding of NAP derivatives to BSA.

Reducing Open‐Circuit Voltage Deficit in Perovskite Solar Cells via Surface Passivation with Phenylhydroxylammonium Halide Salts

Suppressing non-radiative recombination via passivating surface defects of perovskite films has demonstrated an excellent strategy for high-performance perovskite solar cells (PSCs). However, it is still hard to realize both high open-circuit voltage (Voc ) of >1.2Vand high power conversion efficiency (PCE) of >22%,because the optimized bandgap of perovskite films is less than 1.60eV for efficient light harvesting and Voc deficit is generally unavoidable due to carriers recombination. Here, the surface of the perovskite film is treated with a series of phenylhydroxylammonium halide salts and it is found that all of them can remarkably prolong the carrier lifetime owing to their excellent capability of surface defects passivation. The best PSC with phenylbutylammonium bromide treatment realizes a PCE of 22.67% with a Voc of 1.216V, corresponding to a small Voc deficit of ≈344 mV.

Structure, optical and magnetic properties of radical anion, dianion salts and coordination complexes of organic dye 3,4:9,10-perylenetetracarboxylic dianhydride (PTCDA)

Reduction of organic dye 3,4:9,10-perylenetetracarboxylic dianhydride (PTCDA) yields a series of radical anion and dianion salts of PTCDA (1–5). Their formation is accompanied by essential red shift and splitting of absorption bands of pristine PTCDA (493 and 560 nm) which appear nearly in the whole visible range, namely, at 660, 700 and 760–770 nm for the radical anions, and 514–526, 544–569, 633–644 and 700–713 nm for the dianions. Weaker bands are also observed in the NIR range at 954 and 938–940 nm, respectively. Reduction elongates double CO bonds, and the shape of the anions becomes non-planar due to twisting. A dihedral angle between two planar halves of PTCDA increases together with anion charge. The PTCDA•− radical anions form {PTCDA}22− dimers in 1–3 with short interplanar distances of 3.220–3.299 Å. These dimers show intense charge transfer bands at 1460–1480 nm and they are diamagnetic up to 360 K indicating large singlet-triplet energy gap for them. The dianions are diamagnetic in the salts. The PTCDA2− dianion can also form coordination complexes coordinating two potassium cations in {cryptand(K+)}2(PTCDA2−)⋅C6H4Cl2 (6) or vanadocene cation in {cryptand(K+)}(Cp2V+)(PTCDA2−)⋅C6H4Cl2 (7). Mixed {cryptand(K+)}2(PTCDA2−){GaIIICl(Pc•3−)}•−⋅2C6H4Cl2 (Pc: phthalocyanine, 8) salt containing two strongly absorbing anionic chromophores has also been obtained. Both anions are chequered in the layers forming short CO(PTCDA2−)⋅⋅⋅H[GaIIICl(Pc•3−)}•−] hydrogen bonds. Most probably, namely these bonds provide rather effective antiferromagnetic coupling of the [GaIIICl(Pc•3−)}•−] spins (S = 1/2) within the layers with large negative Weiss temperature of −25 K.

Coordination Chemistry and Methylation of Mixed-Substituted Tetraphosphetanes (RP-PtBu)2 (R=Ph, Py).

Synthesis of mixed‐substituted tetraphosphetanes (RP−PtBu)2 (R=Ph (4), Py (5); Py=2‐pyridyl) is achieved from the condensation of dipyrazolylphosphanes RPpyr2 (R=Py (1), Ph (3); pyr=3,5‐dimethylpyrazolyl) as P1‐building block (R−P) and tBuPH2 in an equimolar ratio. Compound 5 is of special interest since the presence of two pyridyl‐substituents as well as the P4‐core allows for a rich coordination chemistry with coinage metal salts [Cu(MeCN)4][OTf], Ag[OTf] and in situ formed [Au(tht)][OTf] (tht=tetrahydrothiophene). Both tetraphosphetanes undergo alkylation reaction with MeOTf to give a series of tetraphosphetanium and tetraphosphetanediium triflate salts with additional methylation of the pyridyl‐moiety in case of 5 resulting in interesting novel cyclic trications. Harsh reaction condition and an excess of MeOTf converts 5 into the cyclic trication [‐P(MePy)PMe2P(MePy)PtBu‐]3+ (13 3+; MePy=1‐methylpyridiniumyl) through the elimination of isobutene. This salt undergoes a complicated rearrangement reaction involving a P−P/P−P bond metathesis to form trication [‐P(MePy)3PtBu‐]3+ (17 3+) when reacted with Me2PPMe2.

Batch Stirred-Tank Green Extraction of Salvia fruticosa Mill. Polyphenols Using Newly Designed Citrate-Based Deep Eutectic Solvents and Ultrasonication Pretreatment

A series of citrate salts were tested as hydrogen bond acceptors to synthesize deep eutectic solvents (DES) based on lactic acid and glycerol, used as hydrogen bond donors. The DES produced were then screened to identify the highest performing system for the effective extraction of polyphenolic phytochemicals from the medicinal plant Salvia fruticosa Mill. (Greek sage). The most efficacious DES was the one composed of lactic acid and sodium citrate dibasic, at a molar ratio of 15:1 (LA-SCDB15). Furthermore, for the first time there has been evidence concerning DES pH and extraction efficiency. Using this solvent, a batch, stirred-tank extraction process was developed, by employing ultrasonication pretreatment and response surface methodology. The optimal settings determined were stirring speed 900 rpm, proportion of DES/water 77% (w/v), and ultrasonication pretreatment time 15 min. By adjusting these optimal settings, the predicted maximum total polyphenol yield was calculated to be 79.93 ± 1.92 mg gallic acid equivalents g−1 dry mass. The examination of temperature effects demonstrated that the batch, stirred-tank extraction stage was very energy-efficient, with a barrier of 7.64 kJ mol−1. Comparison of the extraction of Salvia fruticosa polyphenols with other green processes previously developed, illustrated the high extraction capacity of LA-SCDB15. The major polyphenols identified in the extracts produced under optimized settings were chlorogenic acid, luteolin 7-O-glucuronide and rosmarinic acid.

Experimental and Theoretical Evidence of Spin-Orbit Heavy Atom on the Light Atom 1 H NMR Chemical Shifts Induced through H⋅⋅⋅I- Hydrogen Bond.

Spin-orbit (SO) heavy-atom on the light-atom (SO-HALA) effect is the largest relativistic effect caused by a heavy atom on its light-atom neighbors, leading, for example, to unexpected NMR chemical shifts of 1 H, 13 C, and 15 N nuclei. In this study, a combined experimental and theoretical evidence for the SO-HALA effect transmitted through hydrogen bond is presented. Solid-state NMR data for a series of 4-dimethylaminopyridine salts containing I- , Br- and Cl- counter ions were obtained experimentally and by theoretical calculations. A comparison of the experimental chemical shifts with those calculated by a standard DFT methodology without the SO contribution to the chemical shifts revealed a remarkable error of the calculated proton chemical shift of a hydrogen atom that is in close contact with the iodide anion. The addition of the relativistic SO correction in the calculations significantly improves overall agreement with the experiment and confirms the propagation of the SO-HALA effect through hydrogen bonds.

Rational Optimization of Lewis‐Acid Catalysts for the Direct Amination of Alcohols, Part 1 – Activity Descriptors for Metal Triflates and Triflimides

Herein we report a comparison of Lewis acidity indicators (affinity scales, electronegativity, Fukui functions, global electrophilicity index) with a new in silico Beckett–Childs descriptor based on the build‐up of partial charge, computed by DFT, on phosphine oxide coordinated to a Lewis acid. When applied to a broad series of triflate and triflimide salts, the last descriptor allowed a qualitative description of catalytic activity trends for the model amination reaction of benzyl alcohol with aniline. A high activity for titanium triflimide was predicted and experimentally confirmed.

Synthesis of fused tetrazolo[1,5-b]pyridazine-based energetic compounds

In this study, the synthesis and properties of 6-nitramino-7-nitro-8-aminotetrazolo[1,5-b]pyridazine (1) and its alkali metal salts (2–6) were presented. The hydrolysis of 6-nitramino and 8-amino from 1 was occurred at the specified conditions, which generated a series of alkali metal salts of 6-nitramino-7-nitro-8-hydroxy-tetrazolo[1,5-b]pyridazine (7, 12) and 6-amino-7-nitro-8-hydroxy-tetrazolo [1,5-b]pyridazine (8-11). Their structures were characterized by SXRD, IR, EA, HRMS and NMR, respectively. The thermal stability was investigated by using DTA and TGA techniques. On the basis of ΔfH and ρ, the detonation performances (vD and p) were calculated using EXPLO5 software. The mechanical sensitivities (IS, FS) were also measured. The results show that compounds 1–12 display good thermal stability (Td ​> ​175 ​°C), high energy level (vD ​> ​6700 ​m ​s−1) and low sensitivities (IS ​≥ ​18 ​J) as promising energetic materials.

Synthesis and catalytic application of cyclopentadienyl nickel(II) N-heterocyclic carbene complexes

A series of ester-functionalized benzimidazolium salts 2a–c were prepared by quaternization of 1-{(ethoxycarbonyl)methyl}benzimidazole (1) with 3,5-dimethylbenzyl bromide, 2,5-dimethylbenzyl chloride and 3-methoxybenzyl chloride, respectively. Refluxing 2a–c with nickelocene in THF yielded the neutral cyclopentadienyl NHC nickel(II) complexes 3a–c. Their structures were defined by NMR, IR and elemental analysis techniques. Molecular weights of 3a–c were affirmed by MALDI-TOF mass spectrometry. Catalytic tests of 3a–c were performed in Kumada coupling of some aryl chlorides with phenylmagnesium bromide at 25 °C.

Design and synthesis of amphiphilic 2-hydroxybenzylphosphonium salts with antimicrobial and antitumor dual action

Here we report the synthesis and biological evaluation of a series of new 2-hydroxybenzylphosphonium salts (QPS) with antimicrobial and antitumor dual action. The most active compounds exhibit antimicrobial activity at a micromolar level against Gram-positive bacteria Sa (ATCC 209p and clinical isolates), Bc (1–2 μM) and fungi Tm and Ca, and induced no notable hemolysis at MIC. The change in nature of substituents of the same length led to a drastic change of biological activity. Self-assembly behavior of the octadecyl and oleyl derivatives was studied. QPS demonstrated self-assembly within the micromolar range with the formation of nanosized aggregates capable of the solubilizing hydrophobic probe. The synthesized phosphonium salts were tested for cytotoxicity. The most potent salt was active against on M−Hela cell line with IC50 on the level of doxorubicin and good selectivity. According to the cytofluorimetry analysis, the salts induced mitochondria-dependent apoptosis.

Synthesis and biological activity of new bisbenzofuran-imidazolium salts

A series of novel bisbenzofuran-imidazolium salts were designed and prepared. The in vitro antitumor activity of these derivatives was evaluated against a panel of human tumor cell lines (A549, HL-60, MCF-7, SMMC-7721 and SW480). Results demonstrated that 2-methyl-benzimidazole ring and substitution of the imidazolyl-3-position with a 4-methoxyphenacyl or 2-naphthylacyl substituent were important for promoting cytotoxic activity. Notably, compound 23 was found to be the most potent compound with IC50 values of 0.64–1.47 μM against five human tumor cell lines, and exhibited higher selectivity to MCF-7 and SW-480 cell lines with IC50 values 15.3-fold and 9.1-fold lower than DDP.

Evidence for Electron Transfer between Graphene and Non-Covalently Bound π-Systems.

Hybridizing graphene and molecules possess a high potential for developing materials for new applications. However, new methods to characterize such hybrids must be developed. Herein, the wet‐chemical non‐covalent functionalization of graphene with cationic π‐systems is presented and the interaction between graphene and the molecules is characterized in detail. A series of tricationic benzimidazolium salts with various steric demand and counterions was synthesized, characterized and used for the fabrication of graphene hybrids. Subsequently, the doping effects were studied. The molecules are adsorbed onto graphene and studied by Raman spectroscopy, XPS as well as ToF‐SIMS. The charged π‐systems show a p‐doping effect on the underlying graphene. Consequently, the tricationic molecules are reduced through a partial electron transfer process from graphene, a process which is accompanied by the loss of counterions. DFT calculations support this hypothesis and the strong p‐doping could be confirmed in fabricated monolayer graphene/hybrid FET devices. The results are the basis to develop sensor applications, which are based on analyte/molecule interactions and effects on doping.

Iron Triflate Salts as Highly Active Catalysts for the Solvent‐Free Oxidation of Cyclohexane

Among a series of iron salts, iron triflates revealed as highly active catalysts for the oxidation of cyclohexane by tert‐butyl hydroperoxide into cyclohexanol and cyclohexanone with initial turnover frequencies higher than 10,000 h–1. The structure of the iron complexes under the reaction conditions was studied by combining electron paramagnetic resonance (EPR) spectroscopy and DFT calculations. The coordination of the catalytic iron center readily evolved in the presence of the reaction products, leading ultimately to its deactivation. Iron and organic superoxo intermediates were identified as plausible active species allowing to rationalize the high activity of iron ligated by highly delocalized counter‐anions.

Louis Armand Victor Amedée Cailliot

Amedee Cailliot (1805-1884), a French physician and pharmacist who isolated for the first time several new acids (among them terephthalic) from turpentine, prepared a series of double salts of mercuric cyanide and potassium (and sodium) bromide and several derivatives of pimaric acid.

A Study of the Interaction between Cucurbit[7]uril and Alkyl Substituted 4-Pyrrolidinopyridinium Salts

The interaction between cucurbit[7]uril (Q[7]) and a series of 4-pyrrolidinopyridinium salts bearing aliphatic substituents at the pyridinium nitrogen, namely 4-(C4H8N)C5H5NRBr, where R = H (C0), Et (C2), n-butyl (C4), n-hexyl (C6), has been studied in aqueous solution by 1H NMR spectroscopy, electronic absorption spectroscopy, and mass spectrometry.

FRET Analysis of Ionic Strength Sensors in the Hofmeister Series of Salt Solutions Using Fluorescence Lifetime Measurements.

Living cells are complex, crowded, and dynamic and continually respond to environmental and intracellular stimuli. They also have heterogeneous ionic strength with compartmentalized variations in both intracellular concentrations and types of ions. These challenges would benefit from the development of quantitative, noninvasive approaches for mapping the heterogeneous ionic strength fluctuations in living cells. Here, we investigated a class of recently developed ionic strength sensors that consists of mCerulean3 (a cyan fluorescent protein) and mCitrine (a yellow fluorescent protein) tethered via a linker made of two charged α-helices and a flexible loop. The two helices are designed to bear opposite charges, which is hypothesized to increase the ionic screening and therefore a larger intermolecular distance. In these protein constructs, mCerulean3 and mCitrine act as a donor-acceptor pair undergoing Förster resonance energy transfer (FRET) that is dependent on both the linker amino acids and the environmental ionic strength. Using time-resolved fluorescence of the donor (mCerulean3), we determined the sensitivity of the energy transfer efficiencies and the donor-acceptor distances of these sensors at variable concentrations of the Hofmeister series of salts (KCl, LiCl, NaCl, NaBr, NaI, Na2SO4). As controls, similar measurements were carried out on the FRET-incapable, enzymatically cleaved counterparts of these sensors as well as a construct designed with two electrostatically neutral α-helices (E6G2). Our results show that the energy transfer efficiencies of these sensors are sensitive to both the linker amino acid sequence and the environmental ionic strength, whereas the sensitivity of these sensors to the identity of the dissolved ions of the Hofmeister series of salts seems limited. We also developed a theoretical framework to explain the observed trends as a function of the ionic strength in terms of the Debye screening of the electrostatic interaction between the two charged α-helices in the linker region. These controlled solution studies represent an important step toward the development of rationally designed FRET-based environmental sensors while offering different models for calculating the energy transfer efficiency using time-resolved fluorescence that is compatible with future in vivo studies.

Aluminum chloride‐catalyzed conversion of levulinic acid to methyl levulinate: optimization and kinetics

AbstractBACKGROUNDMethyl levulinate (ML) is a promising green candidate for bio‐based diesel fuels and fuel additives. An effective method for synthesizing ML from levulinic acid (LA) catalyzed by cheap metal salt catalyst under mild conditions was developed. A series of metal salts were screened for the synthesis of ML from LA, and aluminum chloride was identified as a suitable catalyst for this process.RESULTSThe effects of catalyst loading, the molar ratio of methanol to LA, reaction temperature and reaction time on LA conversion and ML yield were investigated. The response surface method was used to optimize the process, and the model validation experiment showed that the predicted values corresponded well with the actual ones. Under the optimum conditions of reaction temperature 343 K, reaction time 1.5 h, aluminum chloride 1.14 g and molar ratio of methanol to LA 8:1, a high ML yield of 95.0 mol% could be obtained. Moreover, a kinetic model was proposed to evaluate the reaction process at a temperature range of 30–70 °C. The first‐order pseudo model was considered most suitable (R2 &gt; 0.99), and the activation energy of the reaction Ea was estimated to be 32.28 kJ mol−1. Investigation of the reuse of the catalyst revealed that it retained good catalytic activity after repeated use for ten times.CONCLUSIONA green and efficient process of ML production from LA catalyzed by the metal salt aluminum chloride was developed. © 2020 Society of Chemical Industry