Dimethylformamide System Research Articles

Recognition of specific monosaccharides by fluorescence change through the suppression effect on excited-state intermolecular proton transfer reactions.

Pyrene-urea derivatives and acetate anions were used to investigate the excited-state intermolecular proton transfer (ESPT) reaction, where a molecule undergoes intermolecular proton transfer to form a tautomer species in the excited state. Since ESPT occurs when intermolecular hydrogen bonds exist between urea compounds and acetate species, we hypothesize that this reaction might be influenced by compounds with hydroxy groups. In this study, cyclodextrins, saccharides, and ethanol were examined to assess the effects of hydroxy groups on the ESPT reaction. After introducing various hydroxy compounds into the urea-acetate system in dimethylformamide, we observed differences in the fluorescence spectra and fluorescence decay curves. These differences indicate varying interactions between the hydroxy compounds and complexes, leading to distinct fluorescence lifetime behaviors, which makes fluorescence lifetime imaging technology particularly suitable.

Electrical conductivity and thermodynamic studies on Sodium Dimethyldithiocarbamate in non aqueous solvents Dimethylformamide (DMF), at different temperatures

This paper threw some light on the behavior of Sodium N,N-Dimethyldithiocarbamate as an electrolyte. The effect of solvents on the conductance of this salt would be discussed via measurements of Λo, ao and KA, since it can be assumed that the different solvents have a little chance to impose great variations on the solvation processes. The conductance method was chosen as a tool to illustrate the electrolyte-solvent interactions. Fuoss–Onsager equation would be tested using Sodium Dimethyldithiocarbamate in presence of dimethylformamide solvent at different temperatures. The conductance of dilute solutions of Sodium N,N-Dimethyldithiocarbamate is measured in Dimethylformamide, at different temperatures (25, 30, 35 and 40 °C). Accurate values of Λo were obtained by applying the (Fuoss–Kraus–Shedlovsky) equation. Finally, the (Fuoss–Onsager) equation was solved to give the correct values of the constants Λo, J, KA and a° (the closest distance of approach) for Sodium N,N-Dimethyldithiocarbamate salt in Dimethylformamide solvent. Λo and a° (solvation) increase with increasing temperatures. Thermodynamic parameters (∆G°, ∆H°, ∆S° and ∆Es) of Sodium N,N-Dimethyldithiocarbamate in Dimethylformamide were calculated from conductance measurements, the activation energy (∆Es), the enthalpy change (heat of association) (∆H°) and the entropy change (∆S°) are positive, however The free energy change (∆G°) values was negative for Sodium N,N-Dimethyl dithiocarbamate in DMF systems studied with increasing the temperature.

Data Determination and Process of Vapor–Liquid Equilibrium of Butane–Butene System by Complex Extractive Distillation Using Salt

The refined utilization of various parts of hybrid residual C4 has received increasing attention, but the mixed C4 is difficult to separate due to complex components and close boiling points. This paper proposes an innovative separation method using complex extractive distillation by adding cuprous chloride ethanolamine (C2H7NO–CuCl) into the conventional extractant, as a complexing agent. The vapor–liquid equilibrium (VLE) data were measured for six different systems, namely, the mixed C4–dimethylformamide (DMF) system and the mixed C4–DMF–C2H7NO–CuCl system, the mixed C4–acetonitrile (ACN) system and the mixed C4–ACN–C2H7NO–CuCl system, and the mixed C4–methyl–ethyl ketone (MEK) system and the mixed C4–MEK–C2H7NO–CuCl system. Results showed that the relative volatility of butane–butene solution was significantly increased with the addition of the complexing agent systems. After careful consideration of various influencing factors, the mixed C4–MEK–C2H7NO–CuCl system was selected as the best extraction separation system, and technological experiments were carried out to further explore its feasibility and advanced nature. Results showed that when the solvent-to-feed ratio (S/F) was 12.5, the reflux ratio of extractive distillation column (R1) was 1.5, and the reflux ratio of solvent recovery column (R2) was 2.5, the purity of butene was more than 97.0%, and the separation yield was more than 95.0%. Furthermore, the solvent-to-feed ratio of complex extractive distillation was only 70% of ordinary extractive distillation, the reflux ratio was only 60% of ordinary extractive distillation, and the stripping temperature of the complex extractive distillation column was only about 423.15 K, which was lower than that of the ordinary extractive distillation column.

A Scalable H2O–DMF–DMSO Solvent Synthesis of Highly Luminescent Inorganic Perovskite‐Related Cesium Lead Bromides

AbstractAll‐inorganic cesium lead bromide perovskites have attracted a lot of attention because of their excellent optical properties that can potentially be applied in various optical devices. However, large‐scale preparation of cesium lead bromide perovskites with outstanding optical performance is still hindered by the poor solubility of CsBr in polar aprotic solvents. In this work, a water/dimethylsulfoxide (DMSO)/dimethylformamide (DMF) system is demonstrated for the synthesis of inorganic cesium lead bromide perovskites, where the introduction of water can effectively address the dissolution issue of Cs+ ions. Large‐scale synthesis of pure‐phase emissive Cs4PbBr6 with a product yield of up to 73% is achieved and the photoluminescence quantum yield of resulting product reaches as high as 76%. The origin of the light emission is further revealed by the photoluminescence evolution of the colored Cs4PbBr6 single crystals. Furthermore, reversible phase transitions between Cs4PbBr6, CsPbBr3 and CsPb2Br5 are achieved by changing solely the water content, which paves the way for the recycle of the mother solution of Cs4PbBr6 without generation of additional hazardous waste. The three‐solvent‐based synthetic approaches enable an economical, robust, and large‐scale production for all‐inorganic cesium lead bromide perovskites.

New Heteroligand Europium and Gadolinium Formate Triazole Dicarboxylates: Synthesis, Structures, and Luminescence Properties

Complexes {(NMe2H2)[Ln(TDA)(HCOO)] ∙ 0.5H2O)} are prepared by the solvothermal synthesis in a water–dimethylformamide (1 : 1) system from a mixture of 1,2,3-triazole-4,5-dicarboxylic acid (H3TDA), NaOH, and Ln(NO3)3 (Ln = Eu, Gd). The crystal structure of the europium complex is determined by X-ray structure analysis (CIF file CCDC no. 1939689). This compound is shown to be the ionic metal-organic framework, where the cavities in the anionic structure of [Eu(TDA)(HCOO)]– are partially occupied by the dimethylammonium cations and water molecules. The study of the luminescence spectra of the gadolinium derivative gives the energy of the triplet level of the H3TDA ligand (~25 300 cm–1), the value of which makes it possible to efficiently sensitize the luminescence of rare-earth metal ions, in particular, Eu3+. The decay kinetics and the emission and excitation spectra of the heterometallic derivatives {(NMe2H2)[Gd1 – xEux(TDA)(HCOO)] ∙ 0.5H2O)} are studied. The dilution of europium with gadolinium results in a substantial decrease in the concentration quenching of the europium luminescence and an increase in the observed lifetimes of the excited state of Eu3+.

Synthesis, characterization, and supramolecular architectures of two distinct classes of probes for the visualization of endogenously generated hypochlorite ions in response to cellular activity

Two distinct classes of compounds, (E)-2-(((3-amino-4-nitrophenyl) imino) methyl)-5-(diethylamino) phenol (SB) and 5-(diethylamino)-2-(5-nitro-1H-benzo[d]imidazol-2-yl) phenol (IM) were synthesized. SB, a bright red colored compound was crystallized in acetonitrile as a triclinic crystal system while IM, yellow colored compound crystallized as a monoclinic crystal system in dimethylformamide by vapor diffusion of diethylether. These compounds were characterized using spectroscopic techniques (IR, UV–visible, 1H, and 13C NMR), and X-ray crystallography. SB and IM displayed classical and non-classical H-bonding involving C-H…O and π…π interactions. These compounds detected hypochlorite ions in aqueous DMSO (1: 9, v/v, HEPES buffer, pH 7.4), and detection was visible via color changes by naked eye. We also performed UV–visible and fluorescence titrations, showing detection limits of 8.82 × 10−7 M for SB and 2.44 × 10−7 M for IM. The fluorometric responses from SB and IM were also studied against different ROS and anions. DFT calculations were performed to strengthen the proposed sensing mechanisms of both SB and IM. Hypochlorite, which is endogenously generated by myeloperoxidase in endosomes, was specifically visualized using SB and IM in lipopolysaccharide-treated RAW264.7 cells. These probes were also used to image the generation of hypochlorite by RAW264.7 cells during phagocytosis of non-fluorescent polystyrene beads.

Effect of gelation time on the microstructures, mechanical properties and cyclization reactions of dry-jet gel-spun polyacrylonitrile fibers

The use of gel spinning technology in the formation of polyacrylonitrile (PAN)-based carbon fibers has led to significant tensile property improvements. PAN, dimethylsulfoxide (DMSO) and dimethylformamide (DMF) solutions were dry-jet spun, gelled in methanol at −20 and −50 °C for different times from 0 to 40 d, and vacuum-dried at 0 °C for 24 h to obtain PAN fibers that were drawn to a drawing ratio (DR) of 4 in a hot glycerin bath at 110 °C, and then to various DRs in a glycerin bath at 155 °C. The effects of gelation time on the microstructures, mechanical properties and cyclization reactions of the gel-spun PAN fibers were investigated. Results showed that the gelation time affected the gel structure and the maximum possible draw ratio. The gelation effects were significant in the first 5-10 d, and were more prominent for the DMSO system than the DMF system. The maximum possible draw ratio, strength and modulus, orientation and crystallinity of the PAN fibers increased with gelation time. The cyclization temperature decreased and the reaction enthalpy increased with gelation time in cyclization, indicating an improved chain orientation and crystallinity with gelation time. Gelation was an important step affecting the microstructures and properties of gel-spun PAN fibers for making high performance carbon fibers.

Selective α‐Monomethylation by an Amine‐Borane/N,N‐Dimethylformamide System as the Methyl Source

AbstractA new and practical α‐monomethylation strategy using an amine‐borane/N,N‐dimethylformamide (R3N‐BH3/DMF) system as the methyl source was developed. This protocol has been found to be effective in the α‐monomethylation of arylacetonitriles and arylacetamides. Mechanistic studies revealed that the formyl group of DMF delivered the carbon and one hydrogen atoms of the methyl group, and R3N‐BH3 donated the remaining two hydrogen atoms. Such a unique reaction pathway enabled controllable assemblies of CDH2‐, CD2H‐, and CD3‐ units using Me2NH‐BH3/d7‐DMF, Me3N‐BD3/DMF and Me3N‐BD3/d7‐DMF systems, respectively. Further application of this method to the facile synthesis of anti‐inflammatory flurbiprofen and its varied deuterium‐labeled derivatives was demonstrated.

Selective α-Monomethylation by an Amine-Borane/N,N-Dimethylformamide System as the Methyl Source.

A new and practical α-monomethylation strategy using an amine-borane/N,N-dimethylformamide (R3 N-BH3 /DMF) system as the methyl source was developed. This protocol has been found to be effective in the α-monomethylation of arylacetonitriles and arylacetamides. Mechanistic studies revealed that the formyl group of DMF delivered the carbon and one hydrogen atoms of the methyl group, and R3 N-BH3 donated the remaining two hydrogen atoms. Such a unique reaction pathway enabled controllable assemblies of CDH2 -, CD2 H-, and CD3 - units using Me2 NH-BH3 /d7 -DMF, Me3 N-BD3 /DMF and Me3 N-BD3 /d7 -DMF systems, respectively. Further application of this method to the facile synthesis of anti-inflammatory flurbiprofen and its varied deuterium-labeled derivatives was demonstrated.

Cyclodextrin-based oral dissolving films formulation of taste-masked meloxicam

This work deals with fast-dissolving drug delivery systems of meloxicam (MX) derived from electrospun polyvinylpyrrolidone (PVP)/2-hydroxypropyl-β-cyclodextrin (HPβCD) nanofiber mats. Electrospinning of solutions with different solvent systems [dimethylformamide (DMF) and ethyl alcohol (EtOH)] was performed. Prepared films were evaluated for morphology, physical, and mechanical properties. MX content, dissolving time, MX release, and cytotoxicity of films were investigated. In vivo studies were also performed in healthy human volunteers. The results showed that MX/HPβCD complexes improved the solubility of MX. PVP also increased MX solubility and the stability of MX/HPβCD complexes. Films were successfully prepared by two solvent systems with fiber in the nanometer range. MX was well incorporated into the films (100% efficiency). The X-ray patterns and DSC experiment indicated an amorphous form of MX. A fast disintegration time and burst release of MX was obtained from EtOH system. Cytotoxicity testing of the films produced by EtOH system proved safer than the DMF system. In vivo studies revealed that films rapidly dissolved in the mouth and had a less bitter taste than MX. These results suggest that electospun films from EtOH system may be a good candidate for fast-dissolving drug delivery systems to increase palatability of dosage forms.

Phase transitions, structures, and rheological properties of hydroxypropyl cellulose–ethylene glycol and ethyl cellulose–dimethylformamide systems in the presence and in the absence of a magnetic field

Phase transitions, structures, and rheological properties of hydroxypropyl cellulose–ethylene glycol and ethyl cellulose–dimethylformamide systems in the presence and in the absence of a magnetic field have been studied. The application of the magnetic-field results in increases in viscosity and supramolecular particle size in solutions of cellulose ethers. Concentration dependences of viscosity and particle size are described by curves with maxima.

Optimization of oxidative desulfurization of Malaysian Euro II diesel fuel utilizing tert-butyl hydroperoxide–dimethylformamide system

Deep oxidative desulfurization of model diesel consisting of thiophene, dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) was investigated with various oxidants followed by extraction step using dimethylformamide (DMF). Response surface methodology based on Box–Behnken design was used to evaluate the effects of the main operating parameters, including the oxidant to sulfur molar ratio (2.0–4.0), oxidation temperature (40–60°C) and oxidation time (10–60min), on the 4,6-dimethyldibenzothiophene conversion. Among the oxidants used; tert-butyl hydroperoxide (TBHP) was led to the highest oxidation of model sulfur compounds. Meanwhile, the statistical results revealed that TBHP/sulfur ratio was the most important parameter followed by oxidation time and oxidation temperature. The optimum oxidative desulfurization conditions for 4,6-DMDBT conversion had been attained at TBHP/sulfur ratio of 3.0, temperature of 48°C and period time of 31min, respectively with the highest conversion of 4,6-DMDBT of 84.5%. The experimental optimum yield fitted-well with the predicted value with less than 5% error. The mechanistic study showed that the reaction between TBHP and 4,6-DMDBT was efficient to produce corresponding sulfoxide, instead of sulfone compound.

Influence of solvent polarity on surface-fluorination of cellulose nanofiber by ball milling

Ball mill-assisted surface-fluorination of cellulose nanofiber was studied for two solvents with different polarity as dispersion/reaction medium. Milling cellulose in neat toluene gave irregular-shaped decrystallized cellulose particles; addition of pentafluorobenzoyl chloride (PFBC) to the system gave partially fluorinated cellulose as thin flakes with smooth surfaces, which maintained original crystallinity. Milling in neat dimethyl formamide (DMF) caused partial dispersion of nanofibers without decrystallization; milling in PFBC/DMF gave more enhanced dispersion of surface-fluorinated nanofibers. Both fluorinated materials were hydrophobic, with water contact angles of 103°–113°. Bulk degree of esterification was 0.20 for toluene and 0.57 for DMF systems. These results show characteristic influences of solvent species in reactive ball milling of cellulose in terms of fibrillation and surface esterification of nanofibers.

A Combined SNIFTIRS and XANES Study of Electrically Polarized Copper Electrodes in DMSO and DMF Solutions of Cyanate (NCO−), Thiocyanate (NCS−) and Selenocyanate (NCSe−) Ions

A SNIFTIRS (subtractively normalized interfacial Fourier transform infrared spectroscopy) and X-ray absorption spectroscopy (XAS) study of electrically polarized copper electrodes in six polar aprotic solvent-based systems is presented. In the systems investigated, i.e. dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO) solutions containing pseudohalide species of cyanate (NCO−), thiocyanate (NCS−) and selenocyanate (NCSe−) codissolved with tetrabutylammonium perchlorate (TBAP), Cu was found to dissolve over a wide range of potentials to produce the corresponding Cu(I) pseudohalide and/or Cu(II) pseudohalide complex ion species. Insoluble deposited films were also observed at higher anodic applied potentials, thought to be CuSCN in the Cu/NCS−/DMSO or DMF systems, and solid K(SeCN)3 in the Cu/NCSe−/DMSO or DMF systems respectively. The presence of the Cu(II) and/or Cu(I) oxidation states in complexes formed by polarization in Cu/pseudohalide ion systems in DMSO was clearly proven using XAS of cell solutions sampled after SNIFTIRS/electrical polarization experiments. In addition, Fourier transform infrared (FTIR) and X-ray absorption near edge spectroscopy (XANES) data obtained from model solutions prepared from mixing Cu(I) and/or Cu(II) salts with the respective pseudohalide ions in DMF and DMSO confirmed the speciation observed in the electrochemical experiments.

New iron tetrazolate frameworks: synthesis, temperature effect, thermal behaviour, Mössbauer and magnetic studies.

The exploration of the FeF3/FeF2-Hamtetraz-HF system in dimethylformamide by solvothermal synthesis evidences two isostructural 3D hybrid fluoroferrates. They are prepared from the same starting mixture at two different synthesis temperatures: 120 °C for [Hdma]·(Fe4(II)Fe(III)F8(H2O)2(amtetraz)4) () and 140 °C for [Hdma]1.5·(Fe4.5(II)Fe0.5(III)F7(H2O)(HCOO)(amtetraz)4) (). Both compounds are characterized by single crystal X-ray diffraction, X-ray thermodiffraction, TGA analysis, Mössbauer spectrometry and SQUID magnetometry. They crystallize in the monoclinic system and are built from two distinct chains connected by aminotetrazolate anions. The first chain ∞(Fe(II)FN4) is common to and and can be found in numerous fluorides. In the second chain ∞(Fe3X12) (X = F, N, O), iron cations adopt both valence states Fe(ii)/Fe(iii). The hydrolysis of DMF implies the formation of a [Hdma](+) cation and a (HCOO)(-) anion. The presence of Fe(3+) in both phases is evidenced by (57)Fe Mössbauer spectrometry. The magnetic properties are studied and two transitions from a paramagnetic regime to a long range ordered state below 30 K and 5 K are identified.

Novel amphiphilic polymeric ionic liquid-solid phase micro-extraction membrane for the preconcentration of aniline as degradation product of azo dye Orange G under sonication by liquid chromatography–tandem mass spectrometry

A novel amphiphilic polymeric ionic liquid membrane containing a hydrophilic bromide anion and a hydrophobic carbonyl group was synthesized in dimethylformamide (DMF) systems using the ionic liquid 1-butyl-3-vinylimidazolium bromide (BVImBr) and the methylmethacrylate (MMA) as monomers. The prepared amphiphilic ploy-methylmethacrylate-1-butyl-3-vinylimidazolium bromide (MMA-BVImBr) was characterized by a scanning electron microscope and an infrared spectrum instrument. The results of solid-phase micro-extraction membrane (SPMM) experiments showed that the adsorption capacity of membrane was about 0.76μgμg−1 for aniline. Based on this, a sensitive method for the determination of trace aniline, as a degradation product of azo dye Orange G under sonication, was developed by liquid chromatography–tandem mass spectrometry (LC–MS/MS). The calibration curve showed a good linearity ranging from 0.5 to 10.0μgL−1 with a correlation coefficient value of 0.9998. The limit of quantification was 0.5μgL−1. The recoveries ranged from 90.6% to 96.1%. The intra- and inter-day relative standard deviations were less than 8.3% and 10.9%. The developed SPMM-LC–MS/MS method was used successfully for preconcentration of trace aniline produced during the sonication of Orange G solution.

Self-formation of 3D interconnected macroporous carbon xerogels derived from polybenzoxazine by selective solvent during the sol–gel process

Polybenzoxazine (PBZ)-based carbon xerogel has been synthesized by a sol–gel process and carbonization. By different solvents, the microstructure of the porous carbon can be tailored for a wide range of desired properties. In addition, a new aspect to produce 3D interconnected macroporous carbon xerogels by selective solvent via self-formation is introduced. Dimethylformamide (DMF), dioxane, and isopropanol are separately used as a solvent during a sol–gel process. The SEM micrographs reveal different structures of carbon xerogel depending on the type of solvent used. Using DMF as a solvent during a sol–gel process and ambient pressure drying, the carbon xerogel shows a similar porous structure to that of a PBZ-based carbon aerogel obtained through supercritical CO2 drying. In the DMF system, a short gelation time is observed (1.15–3 h) due to the fast ring-opening polymerization accelerated by DMF resulting in the formation of 3D interconnected macroporous structure without using any template. Comparing the rates of cluster growth between DMF and dioxane systems, the rate of cluster growth in dioxane system is slower than that of DMF system, implying good miscibility between PBZ and dioxane. Moreover, microporous spherical particles are obtained from the isopropanol system due to the self-micelle-like formation.

Nanocrystalline copper indium selenide (CuInSe2) particles for solar energy harvesting

High quality copper indium selenide (CuInSe2) nanocrystals were synthesized solvothermally at low temperature (180 °C) using selenite salts (SeO32−) as a dual source for metal and chalcogen, and dimethylformamide (DMF) as one of the solvents and the reducing agent. In order to find out the best solvent combinations for this type of reduction reaction, the effects of different co-solvents on the phase and morphology of the final products were studied in detail. Pure phase CuInSe2 with high crystallinity was synthesized in a methanol–DMF (Me–DMF) system. On the other hand, using water–DMF (H2O–DMF) resulted in some impurity and nanocrystals of poor crystallinity. Raman study revealed that CuInSe2 crystals synthesized in Me–DMF and H2O–DMF exhibit different scattering geometries. The difference of the final products obtained from Me–DMF and H2O–DMF systems may be due to the difference in the reducing ability of methanol and water as well as the difference in the interaction force between the two solvents within each system. Different morphologies such as nanoparticles and nanoplates can be obtained by simply varying the precursor concentration in the mixed solvents. The photo-response of the as-synthesized materials in a 3-electrode photo-electrochemical (PEC) cell suggests that these materials have the potential to be used for solar energy harvesting.

Facile Synthesis of Well‐Defined Telechelic Alkyne‐Terminated Polystyrene in Polar Media Using ATRP With Mixed Fe/Cu Transition Metal Catalyst

AbstractThe synthesis of polystyrene (PS) by atom transfer radical polymerization using the Fe(0)/CuBr2 catalytic system in dimethylformamide is reported. The effects of temperature, ligand, initiator structure, and monomer to solvent ratio on the polymerization kinetics are evaluated. PS with high molecular weight, low polydispersity, and telechelic structure are achieved and successfully used for further reinitiation or the copper(I)‐catalyzed Huisgen 1,3‐dipolar cycloaddition click reaction between alkyne‐ and azide‐terminated PS. For the first time, suitable styrene polymerization rates are achieved using this cost‐effective and environmentally attractive catalytic system. This method can be very useful in macromolecular engineering to afford PS‐based materials with well‐controlled structure.

폴리아크릴로니트릴 공중합체의 극세 섬유제조 및 그 물성

The conditions of wet spinning were considered in order to prepare the fine denier of acrylic fiber. Polyacrylonitrile copolymer was synthesized by the copolymerization of acrylonitrile (AN) and methyl acrylate (MA) initiated by an aqueous sulfite-chlorate redox system. Acrylic fiber was manufactured through wet-spinning in a dimethyl formamide (DMF) system. The conditions of wet-spinning were investigated by i-value, spinning speed, diameter of spinneret, draw ratio, water content of spinning dope and morphology of protofiber. The physical properties of fibers were investigated by Instron. In this experiment, the minimum i-value decreased with the decreasing spinneret diameter, an increased spinning speed, and an increased coagulation bath (CBC) concentration. The maximum draw ratio increased with an increased CBC. The optimum CBC and water content of the spinning dope were 60%-65% and 3.5%, respectively. The tenacity at the breaking point increased with a decreased fineness of fiber. The elongation at breaking point was almost the same value as a function of the fineness of fiber.