Dimethylformamide Solution Research Articles

Comparison of the photochemical properties of phthalocyanine and hemiporphyrazine Zn(II) complexes

In DMF (dimethylformamide) solutions containing concentrations of (NEt4)Br (Et = ethyl) between 0.001 and 0.05 M both zinc phthalocyanine (Pc) and hemiporphyrazine (Hp) complexes are dissolved and form species [Zn(Hp)(Br)]–, and [Zn(Pc)(Br)]–. The increase in formation of the hemiporphyrazine bromide adduct is revealed by a linear dependence of the UV–Vis absorption spectrum on the Br– concentration whereas, over the same concentration range, absorption measurements indicate the formation of the phthalocyanine bromide adduct in solution. The x-ray and molecular structure of [NEt4][Zn(Pc)(Br)](H2O)0.33 has been determined showing the coordination of the Br– to the metal center. Photo-induced processes of the Zn complexes were investigated with deaerated solutions in a time scale t ≥10 ns. The 355 nm flash irradiation of [Zn(Hp)(Br)]– produced transient spectra which showed a bathochromic shift of the absorption maximum from 460 nm to 440 nm and an increase of the spectrum rate of decay with increasing Br– concentrations. The initial spectrum is attributed to the (nπ*–LLCTBr→Hp)[Zn(Hp)(Br)]– excited state which reacts with H-atom donors forming a radical [Zn(Hp-H)(Br)]•–. On the other hand, a transient spectrum, λmax ∼600 nm, grows in a time t ≤0.6 µs when [Zn(Pc)(Br)]– is flash irradiated at 355 nm. The photoreactions of these complexes with SCN– and 2-propanol (IPA) were studied. Despite of the apparent similarity between both complexes, IPA was photo-oxidized by both complexes although by different mechanisms, an electron transfer with [Zn(Pc)(Br)]– and an H atom abstraction with [Zn(Hp)(Br)]–. The photo-oxidation of SCN– by [Zn(Pc)(Br)]– but not by [Zn(Hp)(Br)]– makes a remarkable difference between the photochemistries of these complexes.

An alternative strategy for the synthesis of disazo disperse dyes and their application on polyester fabric

Due to the limitations of dye solubility in reaction solvents, the crosslinking reaction between two monoazo disperse dyes will tend to result in low yield and multiple by-products. In this work, an alternative synthetic strategy was used to prepare three disazo disperse dyes, which involved first synthesizing crosslinked coupling components with diisocyanate compounds followed by diazotization with a double diazonium salt. The structures of these new dyes were characterized by nuclear magnetic resonance (NMR), mass spectrometry (MS), and fourier transform infrared spectroscopy (FT-IR) analysis, and the spectral characteristics of the dyes in dimethylformamide (DMF) solutions were evaluated. Three synthesized disazo dyes were applied to the polyester fabrics by high-temperature and hot-melt dyeing processes. The results showed that a higher yield was obtained for all three dyes, and each of the dyes had relatively high molar extinction coefficient and slow dyeing rate on the polyester fabric due to the existence of the double-chromophore. Therefore, a certain amount of carrier or solubilizer had to be added to the dyebath to improve the dyeing rate. At 220 °C for 2.5 min, a satisfactory dyeing effect was achieved, which demonstrated that the disazo disperse dyes exhibited excellent colorfastness properties. Compared with high-temperature dyeing, thermosol dyeing produced higher dye uptake, build-up, and fastness properties, and this process was suitable for the dyeing of polyester fabrics with the disazo disperse dyes.

MIXED-LIGAND GERMANIUM–LANTHANIDE COMPLEXES WITH 1-HYDROXYETHYLIDENEDIPHOSPHONIC ACID AND 2,2’-BIPYRIDINE

There were developed the novel methods for the synthesis of six mixed- metal and mixed-ligand complexes of germanium and rare earth metals (Pr, Nd, Dy, Ho, Tm, Lu) with 1-hydroxyethylidenediphosphonic acid and 2,2´-bipyridine. The compounds have been characterized using various research methods: elemental analysis, mass spectrometry, electrical conductivity, thermogravimetry, IR spectroscopy. It has proved that all complexes are crystal hydrates, belong to heterometallic mixed ligand compounds [Ln(H2O)4(bipy)2]2 [Ge(m-hedp) (m- OH)]6⸱nH2O, Ln=Pr (1); Nd (2); Dy (3); Ho (4); Tm (5); Lu (6); n = 22 (1, 2), 21 (3), 20 (4, 5), 19 (6). Their formation occurs due to the electrostatic interaction of complex cations [Ln(H2O)4(bipy)2]3+ with hexanuclear anions [Ge(m-hedp)(m- OH)]66-. According to the results of measuring the electrical conductivity of dimethylformamide solutions 1–6, it has been established that they belong to triionic electrolytes: λ (in Ohm-1∙сm2∙mol-1) for 1 = 131,3; 2 = 138,8; 3 = 145,8; 4 = 151,1; 5 = 158,3; 6 = 162,7. The cation-anionic type of complexes 1–6 has been confirmed as a result of the analysis of their mass spectrum. The analysis of the mass spectrum showed that the main decomposition direction of the complex is related to the formation of the complex cation fragment [Ln(H2O)4(bipy)2]3+, which corresponds to the most intense peak (m/z = 136, I = 55%). The thermal decomposition of compounds 1–6 includes dehydration, deaquatation, oxidative thermal destruction and the formation of final products as a mixture of Ln2O3 and GeP2O7. On the DTA curves in the interval 70–200 °C the first endothermic effect can be traced, which is accompanied by the removal of a certain number of crystallization and coordination water molecules into the gas phase. Absorption bands of the P-O bond have been detected at ~1053 and ~970 сm-1, that indicates the presence of the fully deprotonated PO32- groups in the composition of complexes. Furthermore, n(OH), ν(Ge–O), d(Ge–OH) bands characteristic for all the previously synthesized compounds with [Ge6(m-OH)6(m-hedp)6]6- anion have been detected in the IR spectra of 1–6. A set of the bands usual for the aromatic molecules n(C–C), das(CH3), ds(CH3), n(Сar=N) has been assigned with 2,2`-bipyridine in the structure of all compounds.

Influence of Tacticity on the Structure Formation of Poly(methacrylic acid) in Langmuir/Langmuir–Blodgett and Thin Films

AbstractA perfect isotactic poly(methacrylic acid) (it‐PMAA) is synthesized and characterized by NMR spectroscopy. Surface pressure versus mean area per repeat unit (π−A) isotherms are recorded and compared with atactic poly(methacrylic acid) (at‐PMAA). it‐PMAA exhibits a π−A isotherm, indicating the formation of a stable Langmuir film. The isotherm has a characteristic pseudo‐plateau at π of ≈11–14 mN m−1 attributed to the creation of worm‐like entities confirmed by atomic force microscopy (AFM) in Langmuir–Blodgett (LB) films. These structures transform into spherical nanoparticles of ≈40 to 80 nm seen in LB films transferred at the end of the pseudo‐plateau of the isotherm. Grazing incidence wide‐angle X‐ray scattering (GI‐WAXS) shows a broad scattering signal (halo‐like) at a q position of ≈11.12 nm−1, revealing the amorphous nature of the nanoparticles. An ordered morphology, however, is observed in thin films prepared by precipitating it‐PMAA from dimethylformamide (DMF) solution under vigorous stirring and coating them on a solid support. Optical microscopy (OM), AFM, and GI‐WAXS reveal more details about the structure. Finally, various structural modifications of PMAAs are explained based on their tacticity and the subsequent hydrogen bonding effects between the carboxylic acid groups.

Phosphomolybdic acid hydrate encapsulated in MIL-53 (Fe): a novel heterogeneous heteropoly acid catalyst for ultrasound-assisted regioselective nitration of phenols.

In this study, a heterogeneous catalyst, PMA@MIL-53 (Fe) (MIL ⇒ Matériaux de l'Institut Lavoisier), has been used to replace the usual mineral acids such as sulfuric acid. A wide variety of nitration methods require the use of a mixture of acids such as concentrated nitric acid and sulfuric acid, which result in producing a large amount of acidic waste. During recent years, the use of the heterogeneous system for the nitration of aromatic compounds has been highly considered and used by chemists due to some specific advantages, i.e. easy separation of the product from the reaction mixture, the possibility of recycling and reusing the catalyst, etc. Herein, the catalyst was synthesized using a metal-organic framework and a heteropoly phosphomolybdic acid. The PMA@MIL-53 (Fe) was prepared using a similar method of MIL-53 (Fe) synthesis. Afterwards, FeCl3·6H2O and 1,4-benzene dicarboxylic acid (BDC) in a dimethylformamide solution were placed in an ultrasound bath and, then, HPA (heteropoly acid) was added to the reaction mixture. The PMA (phosphomolybdic acid) encapsulation in MIL-53 (Fe) was confirmed using various analysis. Under optimal conditions, the catalytic activity of PMA@MIL-53 (Fe) was evaluated in nitration of phenol under ultrasonic waves. Besides, the ratio of the two products of ortho and para was obtained using GC. Optimum conditions were reached after 15 minutes, in such a way that the loaded PMA was 0.02 g under optimal conditions, the efficiencies of ortho-nitrophenol and para nitrophenol were 54.98 and 45.01, respectively.

A Highly Selective Fluorescence Sensor based on Quinoline for the Fluorescence Detection of Al3+ in Aqueous

Abstract:Specific recognition of ultra-trace levels of ions in semi-water using super-quicker methods is still a challenge for environmental monitoring. The development of ion-selective fluorescence sensors for selective detection of Al3+ is an essential task because of the importance of Al3+ to the human body. A fluorescent chemosensor S based on quinoline as a binding and signaling unit has been designed and synthesized in a one-step procedure. More importantly, when Al3+ ions are added to the sensor S, it showed immediate responses toward Al3+ ions in dimethylformamide (DMF) solution with the strong blue fluorescence quenching. And the S detection limit (LOD) of Al3+ in aqueous media (1.0 M) is 1.75x10-7 M. Furthermore, the proposed mechanism of action for sensor S and metal ions has been learned using some research techniques such as FE-SEM, FT-IR, XRD and XPS. Further, the fluorescence chemical sensor specifically recognizes the metal aluminum ion.

A facile synthesis of a copper(I) thiourea sulphate complex and its application for highly efficient chalcopyrite solar cells.

The precursor compound plays a crucial role in the development of low-cost chalcogenide thin-film solar cells via a solution approach. In this work, we report on the synthesis of a new complex [Cu((NH2)2CS)3]2SO4·H2O through a simple redox reaction between inexpensive Cu(CH3COO)2·H2O and thiourea (TU) in water. Using this complex as a copper source, a stable dimethylformamide solution was made and copper indium sulfoselenide CuIn(S,Se)2 thin film solar cells with a high efficiency of 12.2% have been demonstrated.

Evaluation of Lapatinib-Loaded Microfibers Prepared by Centrifugal Spinning.

Lapatinib (Lap) is a lypophilic drug frequently used in cancer treatment; however, due to its limited solubility and permeability, achieving therapeutic dose through oral administration proves to be a challenge. There are various methods for enhancing the solubility of Lap and other similar drugs, one being the preparation of amorphous solid dispersions (ASD). In this study, a Lap-loaded polyvinylpyrrolidone (PVP) fiber mat was created with centrifugal spinning from a PVP/Lap solution in dimethyl formamide and ethanol. The production rate was 12.2 g/h dry fibers, and the fibers had an average thickness of 2.55 ± 0.92 μm. In the differential scanning calorimetry (DSC) thermogram of the fiber mat, the melting peak of the crystalline Lap was not visible, suggesting that Lap was in an amorphous state. A dissolution study was carried out in 0.2 M phosphate buffer saline solution at 37 °C. UV spectrophotometry data indicated that in the sample containing the fiber mat, the Lap concentration was 332 μg/mL (66%) in 10 min, decreasing to 227 μg/mL by 45 min. Meanwhile the crystalline Lap formed a 30-40 μg/mL (6-8%) solution in 5 min, maintaining that concentration. We conclude that centrifugal spinning can be an effective and easy method to produce ASDs.

Aminolysis of Poly-3-Hydroxybutyrate in N,N-Dimethylformamide and 1,4-Dioxane and Formation of Functionalized Oligomers.

The degradation pattern of bacterial poly-3-hydroxybutyrate (PHB) in dimethylformamide (DMF) and dioxane solutions at 100 °C assisted by ethylenediamine, 1,4-diaminobutane and monoaminoethanol was studied. When diamines were introduced into the PHB solution in DMF in the amount of 1 mol of the reagent to 5 or 10 mol of PHB monomers, a rapid decrease in the molecular weight of the polymer was observed. The initial value of the weight average molecular weight (Mw) 840 kDa had decreased by 20-30 times within the first 10-20 min of the experiment, followed by its gradual decrease to several thousand Da. When a similar molar quantity of aminoethanol was added, the molecular weight decreased slower. PHB had been degrading much slower in the dioxane solution than in DMF. By varying the number of reagents, it was possible to reach stabilization of the Mw at 1000-3000 Da when using diamines and 8000-20,000 Da using aminoethanol. 1H NMR analysis of the oligomers revealed of amino and amido groups forming in their structure. From the opposite end of the polymer chain, residues of 3-hydroxybutyric, crotonic and isocrotonic acids were formed during degradation. Differential scanning calorimetry indicated that after oligomerization there was a decrease in the melting point from 178 °C to 140-170 °C depending on the decrease in the molecular weight. The method proposed can be used for obtaining aminated PHB oligomers.

Dinuclear Lanthanide Compound as a Promising Luminescent Probe for Al3+ Ions.

Luminescent probes have wide applications in biological system analysis and environmental science. Here, one novel luminescent dinuclear europium compound with a crown ether analogous ligand was synthesized through a solvent-thermal reaction. Through transformation, upon the addition of Al3+ ions to the N,N'-dimethyl formamide solution of the europium compound, the luminescent intensity of the characteristic emission of Eu3+ decreased, and a new emission peak appeared at 346 nm and increased rapidly. The luminescent investigation indicated that it could act as a highly sensitive and selective luminescent probe for Al3+ ions. Moreover, mass spectrometry and single-crystal X-ray diffraction confirmed the formation of a new more stable trinuclear aluminium compound during the sensing process.

Fabrication of an ultrasensitive and single-use graphite paper based immunosensor for Neuropeptide Y detection: A promising biosensing system for early detection of childhood obesity

The purpose of this study was to develop a label-free impedimetric immunosensing system as an analysis technique for hypothalamic Neuropeptide Y hormone with the goal of determining childhood obesity. A novel process for producing a bioelectrode modified with reduced graphene oxide and its biocompatibility with neuropeptide Y was discussed. The immobilization process is based on the adsorption of reduced graphene oxide (dispersed in dimethylformamide solution) onto a novel graphite paper electrode. Anti-neuropeptide Y antibodies were covalently immobilized on the reduced graphene oxide modified electrode surface using ethyl(dimethylaminopropyl) carbodiimide / N-Hydroxysuccinimide coupling chemistry. Electrochemical impedance spectroscopy and cyclic voltammetry techniques were used to monitor and evaluate all immobilization stages, optimization studies, and analytical characterization of the biosensor. The scanning electron microscopy was used to observe the surface morphology during the immobilization steps of the biosensor. The applicability of the designed biosensor to real serum samples was evaluated for clinical use. The biosensor demonstrated high sensitivity for determining neuropeptide Y in real serum samples. The developed immunosensor had a large linear range (0.005 pg mL -1 -10 pg mL -1 ) and a low limit of detection for neuropeptide Y antigen (0.11 fg mL -1 ). Additionally, the designed immunosensor demonstrated high repeatability, reproducibility, long storage stability (after the fifth week, up to 87% of initial activity), and reusability (20 times). Immobilization scheme of the Neuropeptide Y biosensor

Investigation of solutions of iron(II) complexes with tris(pyrazol-1-yl)methane, possessing the spin-crossover phenomenon

Using methods of static magnetic susceptibility, UV and visible spectrometry and conductometry, dimethylformamide solution of iron(II) complex with tris(pyrazol-1-yl)methane (HC(pz)3) having the composition [Fe(HC(pz)3)2]ns2 (ns = 2-naphthalene sulfonate) has been studied. In solution, as in the solid state, this compound exhibits a spin crossover of 1A1 ↔ 5T2, while in solution it is shifted to a region of lower temperatures and is sharper. It is shown that at a given concentration of 2.5 × 10−4 mol/L at 298 K, the molar electrical conductivity for the [Fe(HC(pz)3)2]ns2 complex in dimethylformamide is Λ298k = 100 ± 2 Ohm−1cm2 mol−1. Solutions of the [Fe(HC(pz)3)2]ns2 complex in a polar aprotic solvent with high dielectric permittivity are characterized by a high degree of dissociation by the type of 1,1-charging electrolyte. The dependences of the logarithm of the electrical conductivity of the studied solutions as a function of the logarithm of concentration and of 1/T are linear. The values of the electrolyte dissociation constant, pK = 2.3, and the activation energy of the charge transfer process, Ea = 5815 J/mol, are calculated. It is shown that a change in the spin state of the central atom of the complex in solution does not lead to changes in the nature of electrical conductivity and does not change Ea.

Functionalization of titania nanotubes surface with platinum(II) complexes

Functionalization of modern materials is one of the possibilities to make them better tailored for human needs. The paper describes a method of covering the titania nanotubes (TNTs) surfaces formed on Ti6Al4V (grade V) titanium alloy with four platinum(II) bimetallic complexes and cisplatin. The first step of the fabricated TNTs modification was their covering with (3-mercaptopropyl)triethoxysilane (MPTES) which plays a role of a bridge between the TNTs and platinum(II) coordination centres. The final application of platinum(II) dimethylformamide (DMF) solutions allowed to form a homogeneous layers of platinum(II) complexes bonded to the TNTs substrate by thiol sulphur atoms of MPTES without visible crystals of physically deposited complexes. The complexes were characterized with XRD, IR, Raman, 1H and 13C NMR spectroscopies, and thermal and elemental analyses. Characterization of titania substrates was done with IR, Raman, SEM, SEM/EDX, XRD, and XPS.

Effect of surface modification of printed electrodes on the performance of supercapacitors

Fused Deposition Modeling (FDM), one of the 3D printing techniques is a low-cost method to print electrodes using conductive polymer composite filaments. In this study, electrochemical performance of EDLC supercapacitor assembled with 3D printed electrodes and two different electrolyte salts (KCl and (NH4)2SO4) in a PVA gel has been analysed. The electrodes are printed using graphene/carbon nanofiber incorporated PLA composite filaments. It is found that post-processing of printed electrodes is necessary to improve the electrochemical performance. Therefore, printed electrodes are sonicated in Dimethylformamide (DMF) solution, which modifies the electrode surface and increases the exposure of conducting materials with electrolyte. Effect of sonication time has been studied by exposing electrodes for 2 min and 10 min. The specific capacitance increases by two orders with 2 min sonication in both KCl and (NH4)2SO4. Also, increasing the sonication time to 10 min decreases the specific capacitance by 43 % for KCl and 23 % for (NH4)2SO4, respectively. This is due to loss of structural integrity of the printed electrode with prolonged sonication time. This study provides a foundation to design more efficient electrodes for EDLC supercapacitors.

Quantitative determination of the N-glycoside derivative of substituted indolo[2,3a]carbazole in innovative dosage forms

Background. A glycoside derivative of indolocarbazole LHS-1269, one of the new drugs selectively affecting tumors, which was first synthesized at the N.N. Blokhin National Medical-Research Center of Oncology of the Ministry of Health of Russia, is of particular scientific interest. Experimental studies demonstrated a multi-target mechanism of action of this compound. LHS-1269 interacts with several intracellular targets and induces various pathways of cell death. Several innovative models of the dosage forms were designed to achieve the highest antitumor activity of the compound and to perform further preclinical studies.Aim. To develop the methods for the quantitative determination of LHS-1269 in pharmaceutical compositions proposed as a result of the search for the optimal dosage form.Materials and methods. The study analyzed the spectrophotometric characteristics of LHS-1269 solutions in dimethylformamide, dimethylsulfoxide (DMSO) and in the mixture of solvents DMSO–ethyl alcohol, as well as electronic absorption spectra of the excipients in the mixture of solvents DMSO–ethyl alcohol. Spectrophotometric measurements were performed on a Cary 100 spectrophotometer (Varian, Inc., Australia) in the wavelength range from 200 to 500 nm. The standard sample is the substance LHS-1269 (N.N. Blokhin Oncology Research Center of the Ministry of Health of Russia).Results. The carried out studies showed that LHS-1269 solutions in dimethylformamide, DMSO and mixture of DMSO– ethyl alcohol are suitable for spectrophotometric measurements. Several variants of the methodology for the assay of LHS-1269 in various dosage form models that differ in the content of the active substance and the excipients composition have been developed: LHS-1269 concentrate for solution for injection and infusion; lyophilisate for solution for injection; liposomal lyophilisate for dispersion for injection.Conclusion. Techniques for the assay of LHS-1269 in dosage form models have been developed. It has been shown that the developed techniques are applicable for LHS-1269 quantitative determination in innovative dosage forms containing polymeric low molecular weightsolubilizers, lipids, cholesterol, mono- or oligosaccharides as excipients.

Computational Study of Some 4’-Aryl-1,2,4-triazol-1-ium-4-R2-phenacylid Derivatives in Vacuum and Dimethylformamide

Four carbanion monosubstituted 4’-aryl-1,2,4-triazol-1-ium-4-R2-phenacylids, used as precursors in obtaining new heterocyclic compounds, and their corresponding derivatives belonging to the C2v point group of symmetry were studied by computational means in dimethylformamide (DMF) solutions compared with their isolated state. The changes in the computed parameters induced by the solvent compared with those of the isolated molecules were analyzed in this paper. The charge distribution and the molecular energies in the HOMO and LUMO, the electronic states responsible for the visible absorption band of 4’-aryl-1,2,4-triazol-1-ium-4-R2-phenacylids, in their isolated state and in solutions achieved in DMF were computed and compared with the visible electronic absorption spectra. The molecular descriptors of the studied compounds were computed, and the higher reactivity of the carbanion monosubstituted 4’-aryl-1,2,4-triazol-1-ium-4-R2-phenacylids compared with symmetric derivatives was established. The obtained results can help researchers to obtain new heterocycles with applications in the drug industry.

Highly Emissive Luminogens in Both Solution and Aggregate States

Highly Emissive Luminogens in Both Solution and Aggregate States

Synthesis of fully divanillic acid-based aromatic polyamides and their thermal and mechanical properties

Fully divanillic acid (DVA)-based aromatic polyamides (R-R′-DVAPAs) having methyl or butyl side chains (R = -(CH2)n-1-CH3; n = 1 or 4) with weight-average molecular weights ranging from 49,000 to 60,000 g mol−1 were synthesized by polycondensation of alkylated DVA-based dicarboxylic acid monomers and diamine monomers. Thermogravimetric analysis of the polyamides found decomposition temperatures at approximately 380 °C and glass transition temperatures of 207 °C–262 °C, depending on the side-chain length, indicating high heat resistance and thermal stability. Differential scanning calorimetry and dynamic mechanical analysis revealed an amorphous structure for the DVAPAs. The DVAPAs showed good solubility in common polar organic solvents, although cast films prepared from dimethylformamide solution were brittle. Thermo-pressed films were prepared at temperatures higher than the glass transition temperature. The film of Bu-Bu′-DVAPA, which has butyl side chains along the fully aromatic main chain, exhibited a maximum tensile strength of approximately 40 MPa. These polyamides are promising as fully bio-based aromatic high-performance plastics.

Over 12% Efficient CuIn(S,Se)2 Solar Cell with the Absorber Fabricated from Dimethylformamide Solution by Doctor‐Blading in Ambient Air

Thin Film Solar Cells In article number 2200150, Weibo Yan, Hao Xin, and co-workers fabricated high quality CuInS2 precursor films from N,N-dimethylformamide molecular precursor solution by doctor-blading in ambient air. CuIn(S,Se)2 solar cells with a power conversion efficiency of 12.54% on a small area and 8.43% on 1 cm2 level have been achieved from doctor-bladed absorbers, demonstrating great potential of the solution approach for the low-cost industrial production of CuIn(S,Se)2 thin film solar cells.

Local Weak Hydrogen Bonds Significantly Enhance CO 2 Electroreduction Performances of a Metal–Organic Framework

Local Weak Hydrogen Bonds Significantly Enhance CO ₂ Electroreduction Performances of a Metal–Organic Framework