Aqueous DMF Solution Research Articles

Tetrakis(2-quinolinylmethyl)ethylenediamine (TQEN) as a new fluorescent sensor for zinc

A new fluorescent sensor for zinc that binds 1 equivalent of zinc ion, N,N,N',N'-tetrakis(2-quinolylmethyl)ethylenediamine (TQEN), has been prepared and characterized. Zinc-bound TQEN exhibits fluorescence around 383 nm upon excitation at 317 nm, while free TQEN emits very weak fluorescence. UV-Vis and 1H NMR spectral changes also detected the binding of TQEN with zinc ion. The crystal structure of zinc complex with TQEN was determined by X-ray crystallography and compared with that of the TPEN-Zn complex (TPEN =N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine). The binding affinity of TQEN with zinc ion is very high (Kd < 1 microM in aqueous dmf solution). Competition experiments reveal that the zinc-binding affinity of TQEN is lower than the parent, strong metal ion chelator TPEN, and comparable to EGTA (EGTA = ethylene glycol-bis(2-aminomethyl)-N,N,N',N'-tetraacetic acid).

A Raman study of aqueous DMF and DMA solutions at low temperatures

Hydrogen bonding in aqueous N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA) solutions was studied by Raman spectroscopy of the OH-stretching spectra of water as functions of solute concentration and temperature (from –50 to 50 °C). The Raman spectra were decomposed successfully into two components (the low- and high-frequency components). The peak area ratio of the low-frequency component to the high-frequency component increases exponentially with decreasing temperature. The frequency of the low-frequency component decreases linearly with lowering temperature down to –50 °C at all solute concentrations (solute mol fraction from 0.3 to 0.7). It is shown that the hydrogen bonds in the clathrate structures around DMA molecules are stronger than those around DMF molecules.Key words: Raman spectrum, DMF, DMA, aqueous solution, low temperature.

Enantioselective reduction of prochiral ketones by chromium(II) amino acid complexes

The reduction of prochiral ketones has been performed by Cr(II) L-amino acid complexes in aqueous DMF solution under mild conditions in good yields and moderate (up to 58%) ee values. The dependence of the yield and enantioselectivity on various factors such as the structure of the ligand, pH and the solvent has also been investigated. A mechanism based on SET from the Cr(II) ion followed by protonation by water and the formation of an organochromium intermediate is also proposed.

Reactivity of supramolecular systems based on calix[4]resorcinarene derivatives and surfactants in hydrolysis of phosphorus acid esters

AbstractThe formation of mixed micelles of amphiphilic calix[4]resorcinarenes with aminomethyl (AMC, PAMC), tris(hydroxymethyl)amide (THAC) fragments and the cationic surfactant cetyl trimethylammonium bromide (CTAB) in water and aqueous DMF solutions (10‐50% DMF) leads to the decrease of the critical micelle concentration of the systems and the increase of the size of the mixed micelles in comparison with CTAB micelles. The catalytic activity of the mixed systems in the hydrolysis of phosphorus acid esters is higher than those of CTAB micelle and AMC, PAMC or THAC aggregates.

Effect of pressure and temperature on volume properties of water-N,N-dimethylformamide mixtures

Specific volumes (ν), isothermal compressibility coefficients ( β T ) and thermal expansion coefficients (α) of the water-N,N-dimethylformamide (DMF) system have been calculated at temperatures T = 278.15 … 323.15 K and pressures up to P = 100 MPa using the data on densities (ϱ) and compressibility coefficients k = ( ν o − ν)/ ν o measured at the atmospheric pressure. It was found, that the composition dependencies ν( x), where x is the mole fraction of DMF, have maxima and minima, and their shape depends on the pressure. The composition dependencies of the isothermal compressibility coefficients β pass through minima at x ≈ 0.15 … 0.20 at all pressures, and the α( x) dependencies have inversion points at various pressures and constant temperatures. it is shown, that the thermodynamic properties of dilute aqueous solutions of DMF are defined by the features of water structure. An increase of pressure, temperature and concentration of a non-electrolyte in the H 2O-DMF system reduces the regularity of the H-bond network of water.

Meso-tetrakis[o-(N-methyl)pyridinium]porphyrin ensembles with axially coordinated cyclodextrin-penetrating phenethylimidazole: reversible dioxygen-binding in aqueous DMF solution.

alpha-Cyclodextrin (alpha CD)-penetrating 2-methyl-1-phenethylimidazole coordinates to the zinc(II) and iron(II) complexes of meso-tetrakis[o-(N-methyl)pyridinium] porphyrinate, giving non-covalently linked alpha CD-porphyrin ensembles; the iron(II) complex can reversibly bind and release dioxygen in aqueous DMF solution.

New hexadentate ligands composed of 1-hydroxy-2(1H )-pyrimidinone, α,ω-diamine and 1,1,1-tris(carboxyethoxymethyl)ethane or tri(carboxybutyl)isocyanurate. Synthesis and characterization of their iron(III) complexes

The successive coupling of 1-benzyloxy-2(1H)-pyrimidinone with α,ω-diamines, 1,1,1-tris(carboxyethoxymethyl)ethane or tri(carboxybutyl)isocyanurate, and final removal of the benzyl protecting group afforded new hexadentate ligands (TEPOHn or TCPOH). The UV/VIS spectroscopic analysis in aqueous solution indicated 1∶1 stoichiometric complexation of the hexadentate ligand with iron(III). The relative stability constants of iron(III) complexes of the hexadentate ligands were estimated to be log K 24.4–26.3 by the competitive reaction with EDTA, suggesting that the stability was affected by the methylene chain length. The standard redox potential E1/2 of Fe(TEPO2) was measured to be –493 mV at apparent pH 8.0 in 50% aqueous DMF solution. This value was approximately 300 mV higher than that of the iron(III) complex of natural desferrioxamine B (DFB). Further, all synthetic hexadentate ligands effectively removed 3–6 times as much iron(III) from human transferrin as DFB even though the ratio of the synthetic ligand to transferrin was one-fifth that of DFB.

Studies on sulfinatodehalogenation: The reaction of polyfluoroalkyl iodides and bromides with sodium Bisulfite

AbstractWithout oxidant, sodium bisulfite reacted with polyfluoroalkyl iodides and bromides in aqueous DMF solution to give the corresponding sulfinates in good yields.

Peroxyl radical formation in aqueous solutions of N,N-dimethylformamide, N-ethylformamide, and dimethylsulfoxide by ultrasound: Implications for sonosensitized cell killing

Sonodynamic therapy, which refers to a synergistic effect of drugs and ultrasound, is a promising new modality for cancer treatment. The sonodynamic effect was found for a number of structurally unrelated compounds, and the underlying mechanisms are still unknown. Recently, Jeffers et al. ( J. Acoust. Soc. Am. 97:669–676; 1995) have shown that the sonodynamic action of nontoxic concentrations of N,N-dimethylformamide (DMF), N-methyl formamide (MMF), and dimethylsulfoxide (DMSO) combined with ultrasound, on killing of cultured HL-60 human promyelocytic leukemia cells, and attributed this toxic effect to unknown short lived reactive species produced from these solutes by ultrasonic cavitation. Using the spin trap 3,5-dibromo-4-nitrosobenzene sulfonate (DBNBS) in nitrogen-saturated aqueous solutions of DMF, MMF, or DMSO exposed to 50 kHz ultrasound, we detected formation of ·CH 3 and ·CH 2N(CH 3)CHO radical adducts for DMF, mostly ·CH 2NHCHO adducts for MMF, and ·CH 3 adducts for DMSO. These radicals were formed either by reactions of the solutes with ultrasound-generated ·H and ·OH radicals (such as ·CH 2R-type radicals in DMF and MMF, and ·CH 3 radicals in DMSO), or by direct pyrolysis of the weak bonds in the solute molecules (e.g., ·CH 3 radicals from DMF). In air-saturated sonicated solutions these carbon centered radicals were converted to the corresponding peroxyl radicals and spin trapped with 5,5-dimethyl-l-pyrroline-N-oxide (DMPO); ·OOCH 2N( ·CH 3)CHO radicals were identified in DMF, ·OOCH 2NHCHO radicals in MMF, and ·OOCH 3 radicals in DMSO solutions. We suggest that these radical species by virtue of their longer lifetimes and higher selectivity, compared to ·OH radicals, which are also formed in sonicated solutions, are the species responsible for sonodynamic cell killing by the combined effect of ultrasound with DMF, MMF, or DMSO.

New Precursors for Barium Metal-Organic Chemical Vapor Deposition. In situ Growth of Epitaxial Barium Titanate Films Using a Liquid Barium Precursor

The synthesis and characterization of two low melting point barium-organic MOCVD precursors, Ba(hfa)[sub 2][center dot]CH[sub 3]O(CH[sub 2]CH[sub 2]O)[sub 5]C[sub 2]H[sub 5] and Ba(hfa)[sub 2][center dot]CH[sub 3]O(CH[sub 2]CH[sub 2]O)[sub 6]-n-C[sub 4]H[sub 9] are reported. The complexes were synthesized by reaction of n-C[sub 3]H[sub 7]NH[sub 3][sup +]hfa[sup [minus]] solutions in DMF with aqueous DMF solutions of Ba(NO[sub 3])[sub 2] and the corresponding polyethers. Single-crystal X-ray structural analysis of 4 reveals a monomeric 10-coordinate, bicapped square antiprismatic configuration about barium with only six of the available seven oxygen atoms of 2,5,8,11,14,17,20-heptaoxatetracosane coordinated, thus leaving a dangling, uncoordinated n-butoxy substituent.

Fourier transform infrared spectroscopy studies of cyanide ion solutions of dimethylformamide and aqueous dimethylformamide

Fourier transform infrared spectroscopy has been used to investigate the behaviour of HCN and alkali metal and tetraethylammonium cyanides in DMF and aqueous DMF. The cyanide ion exists as free ions and ion pairs in pure DMF but as water-solvated and DMF-solvated ions in aqueous DMF. The aqueous DMF solutions can be treated as a pseudo two-phase system with a distribution coefficient of 0.018 between the aqueous and DMF-rich pseudo phases. A kinetic analysis of the cyanide ion – benzyl chloride reaction in DMF and aqueous DMF has shown that the rate constant for the SN2 reaction is markedly decreased with the addition of as little as 2.5% water. This decrease is primarily due to changes in transition state solvation. The SN2 reactions between cyanide ion and benzylmethyl-4-substituted phenylsulphonium perchlorates in 20% aqueous DMF have also been investigated.

Studies on sulfinatodehalogenation. XXVIII. The addition of polyfluoroalkyl iodides to olefins initiated by sodium disulfite

AbstractPolyfluoroalkyl iodides reacted with olefins in aqueous DMF solution of sodium disulfite under mild conditions to give the corresponding 1:1 adducts in good yields, providing a convenient polyfluoroalkylation method. This indicated that RF. radicals were formed in the reaction of polyfluoroalkyl iodides and sodium disulfite. A SET mechanism is proposed for the sulfinatodehalogenation reaction of sodium disulfite.

N-hydroxy amides. Part 9. Synthesis and lron(III) complexes of tripodal hydroxamic acids derived from ω-(N-hydroxyamino)alkanoic acids and tris(2-aminoethyl)amine

Tripodal oligoamide hydroxamic acids with different chain lengths (compounds 8a–d) are prepared via condensation of N-hydroxysuccinimide esters of N-acyl-N-benzyloxyaminoalkanoic acids with tris-(2-aminoethyl)amine. These synthetic trihydroxamic acids form iron(III) complexes in aqueous DMF solution. The behaviour of these iron(III) complexes is investigated in terms of absorption vs pH and of iron(III) exchange reactions with EDTA. A biological assay performed with Aureobacterium flavescens reveals that the trihydroxamic acids have substantial growth-promoting activity although weak relative to that of natural desferrioxamine B.

Studies on protein semisynthesis. I. Formation of esters, hydrazides, and substituted hydrazides of peptides by the reverse reaction of trypsin.

An enzymatic method for converting tryptic peptides into their intermediates for the azide method of peptide synthesis was investigated by using model substrates, Bz-Arg, Bz-Gly-Arg, and Bz-Gly-Lys. The conditions favorite for the formation of the esters, hydrazides, and substituted hydrazides were deduced from the theoretical analysis on the pH and pKa dependence of the synthetic reactions and the pKa values of the substrates in various solvents. The theory based on the empirical relationship between the pKa of amines and the formation constant of the amides (Fersht, A.R. & Requena, Y. (1971) J. Am. Chem. Soc. 93, 3499-3504) indicates that the most favorite amine in the formation of amides is the one with a pKa value equal to the pKa of the carboxyl group and with such amines the amide formation takes place almost quantitatively even in aqueous solutions. Boc- and Cbz-hydrazine were found to satisfy the above condition approximately. The methyl esters of the substrates were formed in 30-35% yields in 50% aqueous methanol at pH near 4.5 by the reverse reaction of trypsin [EC 3.4.4.4]. Bz-Gly-Arg-NHNH2 was formed in a 34% yield in 2 M aqueous hydrazine and in 70-80% yields in 50% aqueous solutions of dioxane, DMF, and DMSO containing 1 M hydrazine at pH near 7. Bz-Gly-Arg-NHNH-Boc and Bz-Gly-Lys-NHNH-Boc were formed quite readily in 90-98% yields in H2O and in 50% aqueous solutions of dioxane, DMF, and DMSO containing 0.5 or 1 M Boc hydrazine at pH from 4 to 5. The Cbz-hydrazides of the peptides were also formed readily in 88-95% yields in the above mixed solvents containing 0.5 M Cbz-hydrazine. The formation constants of the hydrazides in H2O were in good agreement with those predicted by the empirical relationship. The formation constants in the form of log Ke in the mixed solvents calculated by taking the activity coefficients of the reactants as unity were 0.1 to 0.5 lower than the predicted values.

The stereochemistry of sodium dithionite reductions of cyclic ketones

The stereochemistry of reduction of several substituted cyclohexanones, norcamphor, and camphor by sodium dithionite (sodium hydrosulfite, Na 2S 2O 4) in aqueous DMF solution has been studied. The cyclohexanones yield mainly equatorial alcohols while the bicyclic ketones give mainly endo alcohols.

Electron spin resonance study of solute-solute interactions in aqueous solutions containing transition metal ion chelates of 4, 4′, 4″, 4‴-tetrasulphophthalocyanine

The e.s.r. spectra of frozen aqueous-dimethylformamide (dmf) solutions containing binary mixtures of cobalt(II) tetrasulphophthalocyanine (tspc), nickel(II)tspc, copper(II)tspc and zinc tspc have been used to discern various solute–solute interactions. Addition of zinc tspc or nickel(II) tspc to an aqueous solution containing copper(II) tspc has a profound influence on the ability of dmf to bring about the disaggeregation of the copper(II)tspc. The presence of zinc tspc results in a stabilization of the polymeric form of copper(II) tspc while nickel(II) tspc brings about a breakdown of the aggregated form of copper(II)tspc by addition of dmf. There is unambiguous evidence for the formation of a molecular species containing both nickel(II) tspc and cobalt(II) tspc. The e.s.r. spectra of an aqueous–dmf solution containing copper(II) tspc and cobalt(II) tspc provide evidence for the formation of a species in which dissimilar ion coupling occurs between copper(II) and cobalt(II). Spectra due to cobalt(II) tspc were interpreted by an axial model which did not require the inclusion of quadrupole effects.

Hydroxamic acid polymers

AbstractA polymer bearing hydroxamic acid groups and having a high affinity for iron(III) was prepared through the following procedure. Acryloylalanine (III), prepared by the reaction of acryloyl chloride with alanine, was treated with N‐hydroxysuccinimide in the presence of dicyclohexylcarbodiimide to give the N‐hydroxysuccinimide ester (IV). The ester IV was polymerized by using AIBN in dioxane to give polymer V. Treatment of polymer V with methylhydroxylamine in DMF gave the hydroxamic acid polymer II. The water‐soluble polymer II was purified by dialysis or by gel‐permeation chromatography (GPC) on Sephadex G‐25. Analytical GPC on Sephadex G‐200 and Sepharose 4B indicate that the average molecular weight of the polymer is in the range of 5 × 105 to 1 × 106. The presence of hydroxamic acid groups is confirmed by the intense red‐brown color produced by the addition of iron(III) to a 50% aqueous DMF solution of the polymer under acidic conditions. In pure water the polymer‐iron complex precipitates as a tan solid. Iron‐binding studies of the polymer reveal that the iron(III) trihydroxamic acid complex FeA3 forms at low concentrations of iron. At higher iron levels a lower order of stability is apparent, which can be accounted for by the conversion of FeA3 to FeA2+. In contrast, the FeA3 complex of the trihydroxamic acid deferoxamine‐B is stable at all iron levels. These results are consistent with the polymer structure, which for steric reasons would favor a stable complex, FeA2+, between iron and two adjacent hydroxamic acid groups. An FeA3 complex would be expected to have a lower stability as a result of either bond angle strain and atomic compression, or a lower probability in bringing a third hydroxamic acid into position to form the octahedral complex.