Inclusion Of Acetonitrile Research Articles

Realizing rechargeable cathode-free aluminum-ion batteries via regulating solvation structure in aqueous-aprotic electrolytes

Aqueous aluminum-ion batteries (AIBs) are promising candidates for large-scale energy storage due to the abundant resource reserve, high theoretical capacity, intrinsic safety, and low cost of Al. However, the development of aqueous AIBs is constrained by the inefficient Al plating, inevitable parasitic side reactions, and the collapse of the cathode materials. Herein, we propose a novel Al3+/Mn2+ hybrid electrolyte in a water-acetonitrile co-solvent system with a regulated solvation structure to realize cathode-free AIBs. The inclusion of acetonitrile as a co-solvent plays a crucial role in reducing the desolvation energy and suppressing side reactions. The introduction of Mn2+ can enable the reversible plating/stripping of Al-Mn alloy with reduced overpotentials on the anode and deposition/stripping of AlxMnO2 on the cathodic current collector to realize cathode-free AIBs. The architected AIB delivers a high discharge capacity of 397.9 mAh g−1, coupled with superior rate capability and stable cycling performance. Moreover, the cathode-free AIB shows superior low-temperature performance and can operate at −20 °C for over 120 cycles. This work provides new ideas for developing high-performance and low-cost aqueous AIBs.

Evaluation of the Greenness, Whiteness, and blueness profiles of stability indicating HPLC method for determination of Denaverine hydrochloride and benzyl alcohol in pharmaceuticals

Recently, there has been important emphasis in pharmaceutical analysis on the stability of drug formulations and the development of appropriate stability-indicating studies. In this regard, a comprehensive stability-illustrating RP-HPLC approach has been established and validated for the assay of denaverine hydrochloride (DEN) and benzyl alcohol (BNZ) in Sensiblex® Injectable Solution.Different stress conditions were applied to both components, following the guidelines of the International Conference on Harmonization (ICH). Using the isocratic elution technique, DEN, BNZ, and their degradation products were effectively isolated and quantified on an Inertsil C8 column at room temperature. The mobile phase consisted of acetonitrile: water: orthophosphoric acid (80:20:0.1, by volume), and the flow speed was maintained at 0.8 mL/min. Detection was performed at 220 nm using a diode array detector, with concentration ranges of 10.00–30.00 and 5.00–15.00 μg/mL for DEN and BNZ, respectively. The total analysis time was less than five minutes, establishing this novel chromatographic method as a priority for routine quality control analysis of both drugs. The inclusion of acetonitrile was necessary for achieving adequate resolution. The environmental impact was evaluated using three approaches: Green Analytical Procedure Index (GAPI), Analytical Eco-Scale, and Analytical GREEnness metric (AGREE). Additionally, White Analytical Chemistry (WAC) was employed to evaluate the quality (R), ecological impact (G), and economic viability (B) of the developed approach.Additionally, the newly presented Blue Applicability Grade Index (BAGI) metric was also assessed. The final Eco-scale score of 85 and the AGREE score of 0.65 indicate the environmentally friendly nature of the new chromatographic method. The BAGI final score was 82.5, while the overall score of the WAC tool was 91.8, highlighting the method's practicality and utility. DEN exhibits the highest degradation (24%) in acidic conditions, whereas BNZ is particularly susceptible to oxidative degradation, with a degradation percentage of 35%. New four degradation products were formed, and the two investigated compounds were efficiently separated and analyzed in their presence. Further identification of degradation products for DEN and BNZ is strongly recommended, employing a mass spectrophotometric detector. Notably, the novel method is accurate, reliable, economical, and time-efficient. In conclusion, it can be effectively employed for routine quality control and stability assessment of DEN and BNZ in both their pure form and pharmaceutical formulations.

Formation of Ternary Inclusion Crystal and Enantioseparation of Alkyl Aryl Sulfoxides by the Salt of Urea-Modified l-Phenylalanine and an Achiral Amine

Chiral supramolecular hosts comprising urea-modified l-phenylalanines and achiral primary amines were developed, which facilitated enantioselective inclusion of alkyl aryl sulfoxides (3) up to 89% ee owing to the formation of ternary inclusion crystals. From the structural optimization of the components, the combination of N-(phenylcarbamoyl)-l-phenylalanine (1a) and benzhydrylamine (2e) showed the best inclusion ability among the considered supramolecular hosts. The type of the hydrogen-bonding network of ammonium-carboxylate salts 1a·2 was dependent on the steric bulk of combined primary amine 2. The rigid phenylurea moiety of 1a and moderate steric bulk of 2e played an important role in their high inclusion ability. Host 1a·2e afforded two ternary polymorphic inclusion crystals with the inclusion of acetonitrile. Furthermore, the crystal structures of 1a·2e·3 revealed that the inclusion of 3 was assisted by hydrogen bonding to the host and that stereoselectivity reversal occurred for larger sulfoxides, which was attributed to packing variations of one-dimensional hydrogen-bonding networks.

Single-crystal-to-single-crystal transformation of the desolvation of a cyclotriveratrylene–acetonitrile inclusion complex via a gating mechanism with subsequent polymorphism

A cyclotriveratrelyne–acetonitrile inclusion complex is shown to undergo a single-crystal-to-single-crystal transformation upon desolvation to an intermediate phase and it is furthermore demonstrated that the preparation conditions may introduce polymorphism of the apohost. We characterised the as-synthesized and desolvated polymorphs using single crystal (polymorph 1) and powder X-ray diffraction, thermal analysis and gas sorption. Successive data collections on the as-synthesized crystal at 50 °C show that the rotation of a single, unique methoxy group of the host molecule may allow evacuation of solvent molecules from the seemingly non-porous crystal.

ChemInform Abstract: Regioselective Synthesis of 1,2‐ and 1,3‐Diaminothiacalix[4]arenes via Nucleophilic Aromatic Substitution and Their X‐Ray Structures.

Thiacalix[4]arenes bearing two amino groups instead of two hydroxy groups of p-tert-butylthiacalix[4]arene (2) at the distal 1,3- (5b) and proximal 1,2-positions (5c) are regioselectively synthesized via the nucleophilic aromatic substitution (SNAr) reaction of lithium benzylamide with tetra-O-methylsulfinylcalix[4]arenes 4(rctt) and 4(rcct), respectively. The SNAr reaction selectively proceeds at the benzene rings between two neighboring sulfinyl groups of a trans conformation. This is rationalized by the cooperative coordination of a methoxy group with a neighboring sulfinyl oxygen atom toward the metal ion to form a six-membered chelate, through which the amide ion attacks the aromatic nucleus. The N,O-hybrid thiacalixarenes 5b and 5c adopt cone conformations in their acetonitrile inclusion crystals. The distances between adjacent N and/or O atoms of their narrow-rim substituents indicate that the four substituents form a circular hydrogen-bond network but it is weaker than that of original thiacalixarene 2. Compound 5c also adopts a cone conformation in the guest-free crystal. This, combined with the fact that tetraaminated p-tert-butylthiacalix[4]arene 5a adopts a 1,3-alternate conformation in its guest-free crystal, indicates that the intramolecular O⋯N hydrogen bonds, not to mention the O⋯O hydrogen bond, in compound 5c play a crucial role in maintaining a cone conformation in the crystal.

Regioselective synthesis of 1,2- and 1,3-diaminothiacalix[4]arenes via nucleophilic aromatic substitution and their X-ray structures

Thiacalix[4]arenes bearing two amino groups instead of two hydroxy groups of p-tert-butylthiacalix[4]arene (2) at the distal 1,3- (5b) and proximal 1,2-positions (5c) are regioselectively synthesized via the nucleophilic aromatic substitution (SNAr) reaction of lithium benzylamide with tetra-O-methylsulfinylcalix[4]arenes 4(rctt) and 4(rcct), respectively. The SNAr reaction selectively proceeds at the benzene rings between two neighboring sulfinyl groups of a trans conformation. This is rationalized by the cooperative coordination of a methoxy group with a neighboring sulfinyl oxygen atom toward the metal ion to form a six-membered chelate, through which the amide ion attacks the aromatic nucleus. The N,O-hybrid thiacalixarenes 5b and 5c adopt cone conformations in their acetonitrile inclusion crystals. The distances between adjacent N and/or O atoms of their narrow-rim substituents indicate that the four substituents form a circular hydrogen-bond network but it is weaker than that of original thiacalixarene 2. Compound 5c also adopts a cone conformation in the guest-free crystal. This, combined with the fact that tetraaminated p-tert-butylthiacalix[4]arene 5a adopts a 1,3-alternate conformation in its guest-free crystal, indicates that the intramolecular O⋯N hydrogen bonds, not to mention the O⋯O hydrogen bond, in compound 5c play a crucial role in maintaining a cone conformation in the crystal.

Improved separation and detection of picolinic acid and quinolinic acid by capillary electrophoresis-mass spectrometry: Application to analysis of human cerebrospinal fluid

“Quinolinic acid (QA)”, a metabolite of the kynurenine pathway (KP), is implicated as a major neurological biomarker, which causes inflammatory disorders, whereas there is an increase evidence of the role of picolinic acid (PA) in neuroinflammation. Therefore, there is an urgent need to develop new clinical test for early diagnosis of neuroinflammatory disorders. A comparison is made between three different platforms such as high performance liquid chromatography–electrospray mass spectrometry (HPLC–ESI-MS/MS), nano LC–Chip/ESI-MS/MS, as well as the use of cationic (quaternary ammonium) and anionic (sulfonated) coated capillaries in capillary electrophoresis (CE)-ESI-MS/MS. The comparison revealed that CE-ESI-MS/MS method using a quaternary ammonium coated capillary is the best method for analysis of PA and QA. A simple stacking procedure by the inclusion of acetonitrile in the artificial cerebrospinal fluid (CSF) sample was employed to improve the peak shape and sensitivity of KP metabolites in CE-ESI-MS/MS. The developed CE-ESI-MS/MS assay provided high resolution, high specificity and high sensitivity with a total analysis time including sample preparation of nearly 12min. In addition, excellent intra-day and inter-day repeatability of migration times and peak areas of the metabolites were observed with respective relative standard deviation (RSD) of less than 2.0% and 2.5%. Somewhat broader variations in repeatability for a 3 independently prepared coated capillary (total 35 runs each) with % RSD up to 3.8% and 5.8% was observed for migration time and peak areas, respectively. Artificial CSF was used as a surrogate matrix to simultaneously generate calibration curves over a concentration range of 0.02–10μM for PA and 0.4–40μM for QA. The method was then successfully applied to analyze PA and QA in human CSF, demonstrating the potential of this CE-ESI-MS/MS method to accurately quantitate with high specificity and sensitivity.

Thermodynamic characteristics of thermal dissociation of inclusion compounds based on graphite fluorides

Thermal dissociation processes for acetonitrile inclusion compounds based on the polymer fluorographite host matrix C2F x Br0.01·yCH3CN, where x = 0.49–0.92, y = 0.174–0.285, are investigated. Thermodynamic parameters (ΔH°av, ΔS°av, ΔG°298) for deintercalation of the compounds of the first filling step into the compounds of the second step and gaseous guest within temperature range 294–352 K were determined. The effect of the host matrix fluorination degree on the thermodynamic characteristics of the studied processes is demonstrated.

Synthesis and Conformational Properties of Nonsymmetric Pillar[5]arenes and Their Acetonitrile Inclusion Compounds

AbstractThe catalytic cyclocondensation of 1‐butoxy‐4‐methoxy‐2,5‐bis(methoxymethyl)benzene (1d) affords a statistical mixture of the regioisomeric pillar[5]arenes 3a–d in high yield. The alkoxy groups are arranged stereoselectively in a mode so that they avoid steric interactions. The rotation of the benzene rings is, at room temperature, fast in terms of the NMR timescale and leads to a de facto Cs symmetry for 3a–c and a C5h symmetry for 3d. All four structural isomers can encapsulate two CH3CN guest molecules. The structure determinations are based on four crystal structure analyses (constitutions) and NMR spectroscopic measurements (conformations).

Acetonitrile vapour inclusion in single-crystal adsorbents [MII2(bza)4(pyz)]n (MII = Rh, Cu)

We studied acetonitrile vapour inclusion behaviour for flexible single-crystal hosts [M2(bza)4(pyz)]n (M = Rh2+ (1), Cu2+ (2); bza = benzoate, pyz = pyrazine) by adsorption experiments and single-crystal X-ray analysis of the inclusion state. Independent of metal ions, the flexible single-crystal hosts smoothly and reversibly adsorbed acetonitrile molecules up to ca. 2 molecules per M2 unit through an adsorption leap, which indicated the change of crystal phase transformations. The results showed that the acetonitrile inclusion crystals were isostructural with including acetonitrile molecules aligned in a head-to-tail fashion in a 1D channel. The acetonitrile molecules were densely included in the channel compared with those in an acetonitrile crystal, indicating that the flexible hosts provide a suitable field for observing the acetonitrile inclusion structure. While the inclusion crystal structure was independent of metal ions, the adsorption behaviour has a difference in the critical pressure and amount of the adsorption leap, depending on the metal ions in the host skeletons.

Molecular Pacman: Folding, Inclusion, and X‐ray Structures of Tri‐ and Tetraamino Piperazine Cyclophanes

Reaction of piperazine and 1,3-bis(bromomethyl)-2-nitrobenzene under high-dilution conditions yields cyclic trimeric trinitro, tetrameric tetranitro, and pentameric pentanitro piperazine cyclophanes. Reduction of the nitro groups with SnCl(2) under acidic conditions produces the corresponding triamino and tetraamino piperazine cyclophanes. The solution studies of both nitro and amino piperazine cyclophanes at 30 degrees C by (1)H NMR spectroscopy shows symmetrical structures owing to the fast conformational exchange, whereas the low temperature studies of the tetraamino piperazine cyclophane reveals interesting dynamic behavior that indicates additional intramolecular interactions. Careful crystallizations of the trimeric trinitro and triamino and the tetrameric tetraamino cyclophanes resulted in crystals suitable for X-ray diffraction studies. In the crystalline state the amino-functionalized cyclophanes manifest an extraordinary circular intramolecular hydrogen-bonding network that leads to a fixed 3D structure. Hydrogen bonding in the triamino trimer leads to orientation of all three of the amino groups on the same side of the macrocycle, namely, the rcc conformation, whereas the tetraamino tetramer folds into a more compact shell-like conformation. During the crystallization process one acetonitrile guest is enclosed into the cavity of the tetraamino cyclophane, which gives a crystalline inclusion complex with remarkable resemblance to the famous Pacman motif. The folding, which mimics the behavior of some cyclic peptides and pyrroles, is induced by intramolecular hydrogen bonding from the amino groups to the tertiary amine groups of the piperazines. The cavity of the tetraamino tetramer is markedly smaller than in the corresponding, but nonfolded, tetranitro tetramer and the guest/host volume ratio (packing coefficient) for the acetonitrile and the cavity is approximately 50 %, which indicates a good size match for acetonitrile inclusion.

Characterisation of adsorbent resins for the recovery of geldanamycin from fermentation broth

Geldanamycin is a benzoquinone ansamycin, produced by the Actinomycete Streptomyces hygroscopicus var. geldanus, which possesses a broad spectrum antibiotic and anticancer activity. Adsorbent resins are gaining significant application in areas of product recovery, and in particular antibiotic recovery. It was decided to establish how effective such resins could be, for recovery of geldanamycin from fermentation broths, in a solid phase extraction. The extractions were batch adsorptions between the liquid phase fermentation broth, containing the geldanamycin and the solid phase adsorbent resins. The resins assessed were Amberlite XAD-4, 7, 16, 1180 and 1600, and Sepabeads SP-850 and Diaion HP-20. All resins assessed were capable of recovery of in excess of 90% of geldanamycin at a resin concentration of 15 g/l, although resins XAD-16, XAD-1600, XAD-1180 and Diaion HP-20 showed a higher capacity at lower resin concentrations than the others resins. All resins displayed a level of positive selectivity for adsorption of geldanamycin over that of contaminants. It was found that the rate of adsorption were dependant on temperature, where longer adsorption times were required at lower temperatures. The adsorbent resins displayed a wide pH range over which they were effective. The level of contaminant adsorption could be partially regulated through pH control. Inclusion of acetonitrile in the fermentation broth resulted in lower levels of geldanamycin adsorption, however for Diaion HP-20, at a mix of 80% fermentation broth, 20% acetonitrile, approximately 90% of the geldanamycin was adsorbed, but less than 10% of the contaminants present.

Synthesis and characterisation of N-substituted bis-phenols as precursors for unsymmetrical triarylmethane cations

Bis-(4-hydroxy-3,5-dimethylphenyl)(4-aminophenyl)methane derivatives ( 1– 6) are synthesised and characterised. Inclusion of acetonitrile by bis-(4-hydroxy-3,5-dimethylphenyl)(4- N, N′-dimethylaminophenyl)methane is observed in the crystal structure. Cations generated from these compounds have characteristic visible absorptions. An alternative method for generation of these cations from quinone methide namely 4-[(4′-hydroxy-3′,5′-dimethylphenyl)(4- N, N′-dimethylaminophenyl)methylene]-2,6-dimethylcyclohexa-2,5-dienone under very mild condition is described. The characteristic absorption peaks of the cationic species are used to distinguish different isomeric forms.

Response surface methodology in the development of a stacking-sensitive capillary electrophoresis method for the analysis of tricyclic antidepressants in human serum

Stacking methods are very important in overcoming the poor detection limits in capillary electrophoresis (CE). In this paper, the separation and determination of several tricyclic antidepressants by a stacking method is described. The inclusion of acetonitrile (ACN) in the sample causes stacking (transient pseudoisotachophoresis) especially in presence of sodium chloride. An experimental design (central composite design) together with the response surface methodology has been used to find the optimum composition of the separation buffer and the optimal stacking conditions in few experiments. The response functions used are the product of the total resolution by the number of peaks, for the optimization of the separation buffer, and the product of the total resolution by the mean of the peak heights, for the optimization of the stacking conditions. About 28% of the capillary volume is loaded with sample. The calibration curves are linear over the working range (50-300 ng/mL). With a bubble capillary, the limits of detection (LODs) are in the order of 5 ng/mL. For the analysis of serum samples, enrichment with sodium chloride and the protein precipitation with ACN are enough to avoid interferences and to get stacking. Recoveries between 91.6 and 104% and RSD between 0.6 and 12% are obtained in the analysis of samples of lyophilized human serum and non-lyophilized human serum, spiked with the drugs.

1,3-Dipolar Reactions Involving Corannulene: How Does Its Rim and Spoke Addition Vary?

[reaction: see text] Corannulene undergoes 1,3-dipolar reactions with the dipoles, diazomethane, nitrile oxide, and nitrone through its rim and spoke pi bonds; the rim addition yields "one possible" adduct whereas two "regioselective" adducts are formed by spoke addition. Mechanisms of these reactions have been investigated at the B3LYP/6-31G(d) level. Computations show that both rim and spoke additions prefer concerted pathways that lie 2-5 kcal/mol lower in energy than stepwise paths. Stepwise additions can take place in two ways and the activation energies of these two modes differ by 1-2 kcal/mol. A close inspection of the energy profiles reveals that rim addition is more favorable kinetically and thermodynamically than spoke addition in view of lower activation energy and higher exothermicity observed for rim addition. The rim bond of corannulene is more flexible for distortion and also has a stronger double bond (i.e. pi-character) than the spoke bond and this facilitates rim addition over spoke addition. Deformation energy analysis also confirms the above through higher deformation in corannulene from the spoke addition when compared to rim addition. In the spoke addition, regio1 reaction is kinetically more favored than regio2 reaction. Attempts to react corannulene in an endohedral fashion have led to the exohedral adduct. Computed activation energies suggest that corannulene acts as a deactivated dipolarophile compared to ethylene. Even more striking is the observation that rim and spoke double bonds in corannulene are part of the local aromatic system but it shows remarkable reactivity compared to benzene despite the loss of aromaticity during the reaction. This is well indicated by computed NICS values. Inclusion of acetonitrile as solvent through the PCM model increases the reaction rate and exothermicity.

Thermodynamics of Host−Guest Interactions in Lower Rim Functionalized Calix[4]arenes and Metal Cations: The Medium Effect

A new calix[4]arene derivative containing mixed pendant arms in its lower rim, 5,11,17,23-tetra-tert-butyl[25,27-bis(ethylethanoate)oxy-26,28-bis(ethylthioethoxy)]-calix[4]arene, 1, has been synthesized and characterized by 1H and 13C NMR. 1H NMR data carried out in CDCl3, CD3CN, CD3OD, and C3D7NO suggest that as far as acetonitrile is concerned, the hydrophobic cavity is likely to embrace a solvent molecule. It is shown that the hosting capacity of 1 toward metal cations is greater in acetonitrile than in N,N-dimethylformamide and in methanol. Thus, in the former solvent, complexation with various cations (Li+, Na+, Ag+, Ca2+, Cu2+, Hg2+, and Pb2+) occurs while in the latter media, 1 interacts only with Ag+ and Hg2+. This statement is corroborated by 1H NMR, conductance, calorimetric and potentiometric measurements. It is concluded that through molecular inclusion of acetonitrile in the hydrophobic cavity of 1, the hydrophilic cavity of the resulting adduct becomes more receptive to host metal cations than that of the free ligand. In propylene carbonate, the results show that the ligand loses its ability to interact with metal cations. Thus in acetonitrile, selective recognition of 1 for Hg2+ is demonstrated to an extent that the selectivity for this cation is greater by factors of 1.8 × 103, 1.9 × 103, 6.9 × 103, 1.8 × 104, 4.1 × 104 and 4.5 × 104, relative to Pb2+, Na+, Li+, Cu2+, Ag+, and Ca2+, respectively. This statement is supported by the thermodynamic characterization of the complexation process involving these systems in acetonitrile, N,N-dimethylformamide and in methanol. Thus, the medium effect on the binding process is carefully assessed. The results show that replacement of two ester groups in two alternate pendant arms of the tetraester calix[4]arene derivative by thioethyl moieties has altered significantly the binding capacity and the selective behavior of the latter relative to the former. Final conclusions are given.

Stacking of weakly cationic compounds by acetonitrile for capillary electrophoresis

The inclusion of acetonitrile in the sample causes stacking especially in presence of sodium chloride. It is shown here that the type of the separation buffer and the conditions for the stacking of cationic versus anionic compounds are quite different. Anionic compounds stacked better in high ionic strength inorganic buffers such as borate and phosphate, while the cationic drugs and endogenous substances stacked better in amine and zwitterionic buffers. About 10–20% of the capillary volume can be loaded with sample. Shielding against the negative charges of the silica is a critical factor in stacking of the cationic compounds by the acetonitrile in the sample. The ionic strength of the separation buffer and the addition of organic modifiers affected the stacking to a limited extent.

Effect of pH and ions in the sample on stacking in capillary electrophoresis

Concentrating the sample on the capillary called “stacking” is a simple technique that overcomes the poor detection limits of capillary electrophoresis (CE). Understanding the factors that affect the stacking mechanism is vital. Two general stacking methods are used in CE: (1) low ionic strength buffer in the sample (LISS) and (2) stacking by inclusion of acetonitrile (AS) in the sample. As the sample volume, especially in the latter method, is greatly increased we show that the pH, buffer type and ionic strength of the sample affect greatly the plate number, resolution and migration time. Surprisingly, we find inclusion of a pH, molarity or ion type in the sample, different from that of the separation buffer, can greatly improve the resolution and the stacking for some components of the sample, especially for the acetonitrile induced stacking.

Acetonitrile inclusion complexes of piperazine‐based macrocycles

AbstractNew piperazine‐based macrocycles with single small cavities were prepared by using high dilution technique. The inclusion of acetonitrile into the cavity (7, 8) or clathrate formation (3) was studied by 1H‐NMR spectroscopy in solution and by X‐ray diffraction in the crystalline state. The cycle 3 forms a molecular cleft, a molecular pocket, where the acetonitrile molecule is held by four weak N…︁H interactions reinforcing the clathrate formation. The cycles 7 and 8 contain a rigid cavity for an exact sterical fit with the methyl group of a linear compound like acetonitrile. The acetonitrile inclusion complex with 7 proved to be stable under normal conditions and was studied by means of thermogravimetry. It is stable up to 80°C and the breakdown is complete when the temperature is raised over 120°C. Solid‐state IR studies show a shift of the cyano band of 5 cm−1 to smaller wave numbers when compared with free acetonitrile. The acetonitrile methyl group is shielded and in the 1H‐NMR spectrum its signal is shifted to δ = 1.85.

Calixarenes: Structure of an acetonitrile inclusion complex and some transition metal rimmed derivatives

Calixarenes: Structure of an acetonitrile inclusion complex and some transition metal rimmed derivatives