DMF-H2O Mixture Research Articles

Development of C3 symmetric triaminoguanidine-2-naphthol conjugate: Aggregation induced emission, colorimetric and turn-off fluorimetric detection of Co2+ ion, smartphone and real sample applications

Herein, a simple aggregation induced emissive star shaped organic compound LH3 with 2-naphthol moiety was prepared by simple one-pot condensation reaction from low-cost chemicals. Aggregation induced emission (AIE) features of LH3 was established in DMF-H2O mixtures. Further, the cation sensing capability of the probe LH3 was examined towards various metal ions in DMF-H2O (Tris−HCl buffer solution pH 7.4, 8:2, and v/v) by using UV–vis and emission spectral experiments. The probe LH3 exhibits high selective and sensitive detection towards Co2+ ions over different metal ions via colorimetric as well as turn-off fluorometric fashion. Job’s plot analysis and mass spectral measurement confirms the formation of LH3-Co2+ complex (L-Co3) with 1:3 stoichiometric ratio. When the probe LH3 binds with Co2+ in 1:3 ratio, turn-off emission behavior was observed via chelation enhanced quenching (CHEQ) mechanism. To establish the practical application of the probe LH3, the detection of Co2+ ions present in real water was established. The visual noticeable color variation of probe LH3 upon addition of Co2+ ions have been clearly incorporated with a smartphone app via variation in RGB color values to build an on-site analysis of Co2+ ions.

Preparation a novel pyrene-based AIE-active ratiometric turn-on fluorescent probe for highly selective and sensitive detection of Hg2+

Pyren-DT, as an AIE material, is facile prepared for detecting Hg2+ in aqueous. The obtained Pyren-DT sample is characterized via LC-MS and 1HNMR. Pyren-DT shows admirable an aggregation induced fluorescent emission (AIE) character in DMF-H2O mixture solvent with the water volume fraction (fw) beyond 80%. With the fw given at 70%, Pyren-DT probe presents turn-on fluorescent probe property with fluorescent intensity at 462 nm reliably positive linear with concentration of Hg2+. The LOD of the probe reaches 2.88 × 10−8 mol·L−1. The Pyren-DT probe shows good selectivity and sensibility towards Hg2+ and strong anti-interference towards some cations and anions. Pyrene-1-carbaldehyde is produced by the reaction between Pyren-DT and Hg2+. In the detection of real water samples, the probe shows better fluorescence characteristics in the system of river water samples rather than in the tap water samples for detecting mercury ion.

The Reaction of 2-Chloroquinoxaline with Piperidine in DMSO–H2O and DMF–H2O Mixtures: Kinetics and Solvent Effects

The rate constant of the reaction of 2-chloroquinoxaline with piperidine was measured spectrophotometrically using different aqueous solutions containing DMSO or DMF. Whatever the experimental conditions used, this reaction follows pseudo first order kinetics and is not amine catalyzed. Furthermore, the second order rate constant, kA, increases with increasing percentage of DMSO in the solution, in contrast to DMF. The kA values were then correlated with solvent parameters α, β, π*, $$E_{\text{T}}^{\text{N}}$$ and Y. Plots of log10kA against the reciprocal of the dielectric constant at 25 °C were found to be nonlinear in DMSO, while a linear relationship with a negative slope was found in the case of DMF. This difference between the solvents is presumably due to different solvation pathways between their initial and transition states. Thus, activation parameters ΔH#, ΔS# and ΔG# were evaluated and discussed to support this hypothesis. Finally, DFT calculations were performed, using the B3LYP functional and 6-311G(d,p) basis set, to determine optimum molecular geometry. IR, NMR spectra for both reactant and product and were then compared with experimental values.

Electrochemical reduction, radical anions and solvation energies of 1,2,3,4-tetrafluoro-9,10-anthraquinone and its N-piperidyl derivatives in DMF and DMF–water mixtures

The electrochemical reduction of 1,2,3,4-tetrafluoro-9,10-anthraquinone and its 2-(N-piperidyl) derivative in DMF and DMF–H2O mixtures represents an EE-process, whereas that for 1-(N-piperidyl) and 1,4-di(N-piperidyl) derivatives occurs as an EEC-process. Based on the linear dependences of the first reversible one-electron reductive half-wave potentials of these compounds on the water content of DMF–H2O mixtures, the corresponding changes in the free energies of solvation under electron transfer have been calculated. Radical anions of the above compounds were obtained in DMF and characterized by EPR spectroscopy and DFT calculations at the (U)B3LYP/6-31+G* level of theory.

Coumarin-Pyrazole Hybrid with Red Shifted ESIPT Emission and AIE Characteristics - a Comprehensive Study.

The newly synthesized three coumarin pyrazole hybrid excited state intramolecular proton transfer (ESIPT) dyes show efficient charge transfer from the pyrazole ring and the coumarin towards the electron withdrawing dicyanovinylene group as revealed from the frontier molecular orbitals. Aggregation induced emission enhancement (AIEE) studies with 2-((3-(4-hydroxy-2-oxo-2H-chromen-3-yl)-1-phenyl-1H-pyrazol-4-yl)methylene) malononitrile showed 9 fold increase in the emission enhancement in 90% DMF-H2O mixture. Lippert-Mataga theory explained the solvatochromic behavior of the dyes in various solvents. The charge transfer characteristics and non-linear optical (NLO) properties have been supported and correlated with bond length alternation, bond order alternation and vibrational spectrum. As values of bond order alternation (BOA) tend to be more towards negative and as the value of α increases β decreases while the values of γ depends on the values of α and β. The observed values of γ are positive which revealed that β contributes significantly. The dyes exhibit linear and NLO properties superior to urea. (E)-2-(3-(2-(3-(4-Hydroxy-2-oxo-2H-chromen-3-yl)-1-phenyl-1H-pyrazol-4-yl)vinyl)-5,5-dimethylcyclohex-2-en-1-ylidene) malononitrile shows enhanced linear and non-linear properties among the three dyes.

Stimuli-responsive luminescent coumarin thiazole hybrid dye: Synthesis, aggregation induced emission, thermochromism and DFT study

Novel coumarin thiazole hybrid dye with azomethine linkage was synthesized. The dye is very sparingly soluble in DMF and insoluble in other solvents. The dye shows 2 fold increase in emission enhancement on aggregation caused at 60% DMF-H2O mixture. Differential thermal analysis revealed a change from one polymorph to the other polymorph at 285 °C leading to emission in the red region. Excited State Intramolecular Proton Transfer takes place with thiazole nitrogen atom and not with N atom of azomethine linkage contrary to Pigment Yellow 101. High color value (K/S = 10.42) and light fastness (rating = 8) properties were found as compared to Pigment Yellow 101. The computed absorption and emission values were found closer to the experimental values. The pigment exhibits higher first and second order hyperpolarizabilities (24 times more α0, 248 times more β0 and 756 times more γ value than urea).

The structural diversity, band gap energy and photoluminescence properties of thiophenedicarboxylate based coordination polymers

A series of 2,5-thiophenedicarboxylic acid (TDC) ligand based coordination polymers were solvothermally synthesized, namely, 1, [Mg3(OH)2(H2O)4(TDC)2]; 2, [NH2(CH3)2]2[Mg3(TDC)4]; 3, [Mg2(TDC)2(DMF)2]; 4, [Zn2(TDC)2(bpe)](solvent)X; and 5, [(CH3)2NH2][In(TDC)], where DMF = N,N′-dimethylformamide and bpe = 1,2-bis(4-pyridyl)ethane. Compound 1 was synthesized in a MeOH–H2O solvent mixture and it has a two dimensional layered structure. Compound 2 was obtained using a DMF–H2O mixture and it has a three dimensional structure. It contains Mg3O16 trimeric units which are linked by TDC anions to form the three-dimensional connectivity. Compounds 3 and 5 were synthesized using only DMF as a solvent and compound 4 was synthesized using a DMF–MeOH mixture. Compound 3 also has a three-dimensional structure where Mg4O20 clusters are linked through the TDC anions. Compounds 4 and 5 have three-dimensional structures with a 2-fold interpenetration. All the compounds are characterized well through powder X-ray diffraction, IR spectroscopy, photoluminescence spectroscopy and thermogravimetric analysis. Interestingly compound 5 crystallizes in a chiral space group which has been confirmed by solid state circular dichroism (CD) spectroscopy. We have measured the optical band gap energy for all the compounds and the results showed that the band gap energy varies from 3.44 eV to 3.86 eV. This variation in the band gap energy may be due to the difference in structural arrangement.

Structure–function relationship of electrodeposited MoSx film in N, N-dimethyl-formamide/H2O mixture solvent as electrocatalyst for hydrogen evolution

Nanostructured plate-like island molybdenum sulfides (MoSx) film has been synthesized successfully through a facile one-step electrodeposition method from the mixture solution of N, N-dimethyl-formamide (DMF) and H2O. The effect of different ratio of DMF to H2O on the MoSx film has been investigated. Scanning electron microscopy (SEM) shows that when the ratio of DMF to H2O is 1:20, the as-prepared MoSx film exhibits maximum island structures, exposing most edges and rims. The electrochemical measurements confirm that MoSx film deposited in the mixed solution of VDMF: VH2O = 1:20 has the best hydrogen evolution reaction (HER) activity, with an overpotential of 80 mV. The improved HER activity may be attributed to the polarity difference of DMF-H2O and morphology directing of DMF. Therefore, using DMF–H2O mixture solution with the appropriate ratio may be a facile and effective way to prepare the excellent electrocatalysts for HER.

Viscosity of Urea in the Mixture of N,N-Dimethylformamide and Water

The viscosity of urea (U) in the mixtures of N,N-dimethylformamide (DMF) and water (H2O) was measured within the temperature range from (293.15 to 308.15) K. The results obtained were used to calculate the dynamic viscosities, η, of the DMF–H2O mixture and urea in aqueous DMF solution. Based on the relative viscosity values calculated, ηr, and Jones–Dole’s equation, the values and sign of viscosity coefficient B were determined and analyzed on account of the destructive or constructive properties of urea regarding the solvent structure. The data obtained were discussed from the point of view of temperature changes and interactions in solutions.

Polymer-assisted dispersion of carbon nanotubes and silver nanoparticles and their applications

We report a family of novel dispersants that are highly effective for finely dispersing carbon nanotubes (CNT) and silver nanoparticles (AgNPs) in aqueous medium. The imide functionalized dispersants were prepared from the amidation of diamine and dianhydrides such as 4,4′-oxydiphthalic dianhydride, 4,4′-carbonyldiphthalic anhydride and pyromellitic dianhydride. The poly(oxyalkylene)-diamines with different backbones including poly(oxypropylene) (POP) and poly(oxyethylene) (POE) were allowed to react with dianhydride at 2 : 1 to 7 : 6 molar ratio under the conditions of condensation at 150 °C. The amidoacid intermediates were readily converted into cyclic imide structures as the thermodynamic products, as characterized by Fourier transform infrared. These copolymers were screened for the dispersed ability for CNT in a DMF–H2O mixture, characterized by UV-visible absorption. The comparison identified that the amine-terminated and POE-segmented imide (POE-imide) at >6 : 5 of amine/anhydride ratio was more effective for dispersing CNT than the anhydride-terminated imide analogs and POP-segmented imide. The tandem procedures of dispersing CNT and then AgNPs were developed by in situ reduction of AgNO3 in the presence of the POE-imide dispersant. As a result, the homogeneous dispersion of mixtures of CNT-tethered AgNPs (20–30 nm in diameter) and free AgNPs (8–30 nm) was prepared. Furthermore, the AgNPs/CNT nanohybrid was also isolated by centrifugation and removal of the free AgNPs, and characterized by transmission electron microscopy and we prepared a conductive film (10 μm) with the conductivity of 103 to 105 S cm−1 by controlling the annealing temperature in air.

Volumetric Properties of Urea in the Mixture of N,N-Dimethylformamide with Water

The density of urea (U) in the mixtures of N,N-dimethylformamide (DMF) and water (H2O) was measured within the temperature range of (293.15 to 308.15) K. The results obtained were used to calculate the excess molar volume, VE, of the DMF–H2O mixture, apparent molar volumes, VΦ, of DMF in water and of water in DMF, as well as the partial molar volume of urea in a solution at infinite dilution, Vm∞, within the whole concentration range of the mixed solvent (DMF–H2O). The data obtained were discussed from the point of view of temperature changes and interaction in solution.

Peculiarities of the mechanism of electroreduction of cinnamic acid in DMF and DMF-H2O mixture

The electrochemical behavior of cinnamic acid (CA) on the cathodes with a high hydrogen overpotential (Hg, glassy carbon, and carbositall) in the aprotic solvent (DMF) and in DMF with additions of H2O or Et4NOH is studied by the methods of polarography, preparative electrolysis, cyclic voltammetry (CVA), coulometry, and chronoammetry. It is found that the mechanism of CA electroreduction is in conflict with the classical notion of the mechanism of electroreduction of α,β-unsaturated carboxyl compounds. It is shown that in the aprotic solution, in contrast to similar carbonyl compounds or ethers, which are the derivatives of organic acids, the products of double-bond hydrogenation, rather than the dimeric compounds, are the only products of CA electroreduction, i.e the presence of carboxyl group changes essentially the direction of electrochemical process. From the data of CVA, it is concluded that stable dimeric associates are present in the DMF solutions in the equilibrium with nondissociated CA.

Electrochemical hydrogenation of 3-(methoxyphenyl)propenoic acids

Electrosynthesis can successfully be used for double bond hydrogenation in 3-(methoxyphenyl)propenoic acids. The corresponding 3-(methoxyphenyl)propanoic acids were produced in a virtually quantitative yield under the conditions of both electrocatalytic hydrogenation at the Ni cathode modified by electrodeposited dispersed nickel in a DMF-H2O mixture in the presence of AcOH and direct electroreduction using mercury and glassycarbon cathodes in DMF with Bu4NClO4 as the supporting electrolyte, although the mechanisms of these processes are different.

Cyanide Detection with Heterocyclic Quinoid Compounds

Compound 2 was found to selectively detect cyanide ions in DMF-H2O mixtures (99:1) at ambient conditions with a detection limit of 1.0 µM.

Self-assembled micelles of N-phthaloyl-carboxymethychitosan for drug delivery

Micelles were self-assembled from N-phthaloyl-carboxymethylchitosan (CMPhCh) in a DMF-H 2O mixture solution, and they were used to evaluate drug deliveries of levofloxacine hydrochloride (Lfloxin) and bovine serum albumin (BSA). Their morphologies and the physical properties were investigated by X-ray diffraction patterns, fluorescence intensity, and transmission electron microscopy (TEM). The results indicated that the critical micelle concentration (CMC) of CMPhCh in aqueous solution was 0.20 mg/mL. The CMPhCh loaded with Lfloxin exhibited micelles having 60–90 nm diameters, whereas that with BSA displayed vesicular shape with 30–200 nm diameters. Moreover, the Lfloxin and BSA could be controlled to release within 72 h in sodium phosphate buffer (pH 7.4), indicating promising applications of the CMPhCh micelles in the drug delivery and release fields.

Suzuki Reactions of Aryl Bromides Catalyzed by Hydroxyapatite-Supported Manganese

Abstract Suzuki cross-coupling reactions between aryl bromides and phenylboronic acids were studied over a hydroxyapatite-supported Mn catalyst (MnHAP) for the first time. An increased yield was obtained over the fluoride ion-exchanged hydroxyapatite-supported Mn catalyst (MnFAP). Under optimized conditions, the yield was about 70%. The effect of solvent compositions and different substituents were studied over the MnFAP catalyst. The DMF-H2O mixture with a DMF/H2O volume ratio of 1/3 was the best solvent. Moderate yields (18%–46%) were obtained for all tested aryl bromides and phenylboronic acids substituted by different groups.

Synthesis and characterization of polystyrene–poly(ethylene oxide)–heparin block copolymers

AbstractA procedure for the preparation of new block copolymers composed of a hydrophobic block of polystyrene, a hydrophilic spacer‐block of poly(ethylene oxide) and a bioactive block of heparin was investigated. Polystyrene with one amino group per chain was synthesized by free radical oligomerization of styrene in dimethylformamide, using 2‐aminoethanethiol as a chain transfer agent. This amino group was used in the coupling reaction with amino‐telechelic poly(ethylene oxide) to produce an AB type diblock copolymer with one amino group per polystyrene (PSt)–poly(ethylene oxide) (PEO) chain. The amino‐semitelechelic oligo‐styrene was converted into the isocyanate‐semitelechelic oligo‐styrene using toluene 2,4‐diisocyanate and subsequent coupling with H2N–PEO–NH2 afforded AB type block copolymers with terminal amino groups. The coupling of PSt–PEO–NH2 with heparin was performed in a DMF–H2O mixture, first by activating the heparin carboxylic groups with EDC at pH 5.1–5.2 and subsequently reacting the activated carboxylic groups with the amino groups of the PSt–PEO–NH2 at pH 7.5. Depending on the molecular weights of the diblock copolymer used 25–29% w/w heparin was incorporated. These polymers will be further evaluated for their blood‐compatibility.

Intermediates in reactions of the diimine complex trisferrozineiron(II) with hydroxide or cyanide in binary aqueous solvent mixtures and in micelles

Kinetic and spectroscopic observations are reported for the reaction of tris-ferrozineiron(II) with hydroxide in DMSO- and DMF-H2O mixtures and with cyanide in MeOH- and DMSO-H2O mixtures. Micellar effects (CTAB) are described for the reactions of tris-ferrozineiron(II) and of tris-5-sulphonato-1,-10-phenanthrolineiron(II) with hydroxide. Results for the ferrozine complex are discussed in terms of mechanisms involving intermediates formed by attack of hydroxide or cyanide at the coordinated ligand.