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PubMed1996

Alterations of hepatic drug metabolising system due to dimethylformamide (DMF).

The effect of repeated exposures to N, N-dimethylformamide (DMF) on the liver and the hepatic microsomal monooxygenase system and glutathione metabolizing enzymes were investigated. DMF was administered to Wistar male rats by subcutaneous (s.c.) injection at 1.0 ml/kg body weight (950 mg/kg), 3 times a week for 2 weeks. The gain in the body weight in the DMF group were suppressed compared with the control group at 2 week. The relative weight of the liver, spleen and kidney also appeared to increase in the DMF group as same as in the control group. Hematological examinations showed no changes. Glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) did not change in the DMF group. Hepatic microsomal protein and cytochrome P-450 did significantly decrease by 30% and 38%, respectively, while there was no change in cytochrome b5, NADPH-cytochrome c reductase and NADH-ferricyanide reductase. Glutathione peroxidase (GPx) activity was not affected by DMF administration, while glutathione reductase (GR) and glutathione S-transferase, (GST) activity were significantly increased by 16% and 64%, respectively. These results indicate that DMF alters tke hepatic drug metabolizing system without significant increase of the serum transaminase levels. These findings may contribute to elucidate the mechanism of DMF hepatotoxicity.

Animals↗

PubMed1996

[Studies on cell-mediated immunotoxicity of dimethylformamide].

Pathological examination of the immune organs, pedal pad swelling experiments, alpha-acetate naphthalol esterase stain for peripheral blood lymphocyte, spleen cell interleukin-2 (IL-2) release, in vitro concanavalin-A (Con-A)-induced lymphocyte proliferation test were carried out to study the effects of dimethylformamide (DMF) on the animal immune organs and its cellular immunotoxicity. Results showed DMF could lower the relative weight of spleen and thymus and decrease significantly reaction value of pedal pad swelling mediated by sheep red blood cell in mice. Exposure to DMF through subcutaneous injection and gastric instillation could cause the decrease of peripheral ANAE-positive lymphocyte in different species of animals. Exposure to DMF at doses of 1/10 and 1/160 LD50 could significantly cause decrease of IL-2 release. Tests in vitro showed DMF with doses of 10-150 mmol/L could inhibit significantly lymphocyte proliferation induced by Con-A. It suggests DMF has effects on cellular immunotoxicity in mice.

Animals↗

PubMed1998

Dimethylformamide-induced occupational liver injury--a case report.

Dimethylformamide(DMF), a widely used industrial solvent, has been reported to induce subtle to clinically overt hepatotoxicity. Liver injury due to occupational exposure through inhalation and skin contact have been sporadically reported. We reported a 42-year-old male Taiwanese who developed progressive, intermittent abdominal pain for 6 months after working in a synthetic leather factory. Acute hepatitis episode occurred after working in an enclosed and poorly-ventilated workplace for one day. Based on occupational history, pathological examination and serial liver function examinations, the case was compatible with DMF-induced acute chemical hepatitis.

Adult↗

PubMed2003

Biological monitoring of workers exposed to N, N-dimethylformamide in synthetic leather manufacturing factories in Korea.

OBJECTIVES: To investigate the relationship between N, N-dimethylformamide (DMF) exposure and excretion of urinary N-acetyl- S-( N-methylcarbamoyl)cysteine (AMCC) and N-methylformamide (NMF) in workers at synthetic leather manufacturing factories in Korea, for the first time. METHODS: One-hundred forty-four male workers at nine synthetic leather manufacturing factories were surveyed. Exposure to DMF was evaluated through breathing zone air sampling followed by analysis via a gas chromatograph equipped with a flame ionization detector (GC-FID). The levels of NMF and AMCC were determined by a GC with a flame thermionic detector (GC-FTD). Urine samples were collected at the end of the workshift. RESULTS AND CONCLUSIONS: Geometric mean of workplace air DMF and urinary NMF was 8.8 ppm and 47.5 mg/l, respectively, and the level of DMF and NMF was significantly correlated. The biological exposure limit for NMF (15 mg/ml) was exceeded in 89.5% of urine samples, and 37.9% of air samples exceeded the environmental DMF exposure limit (10 ppm), indicating a serious health risk to the employees of the synthetic leather industry in Korea. Exposure to 10 ppm DMF in the workplace air corresponded to a urinary NMF concentration of 53.4 mg/l. Alcohol intake the day before urine was sampled influenced NMF excretion into urine (40.5 mg/l NMF for the no-alcohol group and 94.6 mg/l for the group consuming more than 63.0 g alcohol/day). We could not find a significant relationship between air DMF and urinary AMCC concentration. Exposure to 10 ppm DMF corresponded to an AMCC concentration of 8.0 mg/l in the urine samples collected on the same day as the air was sampled.

Acetylcysteine↗

PubMed2005

Low-temperature (180 K) crystal structures of tetrakis-mu-(niflumato)di(aqua)dicopper(II) N,N-dimethylformamide and N,N-dimethylacetamide solvates, their EPR properties, and anticonvulsant activities of these and other ternary binuclear copper(II)niflumate complexes.

Two pseudopolymorphs, solvates, of [Cu(2)(II)(niflumate)(4)(H(2)O)(2)] of unknown structure were obtained following solution of [Cu(2)(II)(niflumate)(4)(H(2)O)(2)] in N,N-dimethylacetamide (DMA) or N,N-dimethylformamide (DMF). Low-temperature crystal structures obtained for these solvates revealed that they were ternary aqua DMA and DMF solvates: [Cu(2)(II)(niflumate)(4)(H(2)O)(2)].4DMA and [Cu(2)(II)(niflumate)(4)(H(2)O)(2)].4DMF. Intermolecular hydrogen bonding interactions account for the formation of these stable DMA and DMF solvates. These pseudopolymorphs contain a centrosymmetric binuclear center with Cu-Cu bond distances ranging from 2.6439(7) to 2.6452(9) A; the coordination sphere of Cu(II) is characterized by one long Cu-O (water) bond length of 2.128(3)-2.135(3) A and four short Cu-O (carboxylate) bonds of 1.949(3)-1.977(3) A. Crystal parameters for the DMA pseudopolymorph: a=10.372(1), b=19.625(2), c=17.967(2) A, beta=97.40(1) degrees , V=3626.8(6) A(3); monoclinic system; space group: P2(1)/a and for the DMF pseudopolymorph: a=10.125(2), b=18.647(3), c=19.616(4) A, alpha=74.38(2)(o), beta=88.18(2)(o), gamma=79.28(2)(o), V=3504(1) A(3); triclinic system; space group: P1. EPR spectra of these solids are identical and show strong antiferromagnetic coupling between the copper atoms, similar to the spectrum obtained for [Cu(2)(II)(niflumate)(4)(DMSO)(2)]. The [Cu(2)(II)(niflumate)(4)(H(2)O)(2)], [Cu(2)(II)(niflumate)(4)(H(2)O)(2)].4DMA, [Cu(2)(II)(niflumate)(4)(H(2)O)(2)].4DMF, [Cu(2)(II)(niflumate)(4)(DMF)(2)], and[Cu(2)(II)(niflumate)(4)(DMSO)(2)] evidenced protection against maximal electroshock-induced seizures and Psychomotor seizures at various times after treatment, consistent with the well known antiinflammatory activities of Cu chelates, but failed to protect against Metrazol-induced seizures while evidencing some Rotorod Toxicity consistent with a mechanism of action involving sedative activity.

Animals↗

PubMed1980

Glass capillary column gas chromatography of barbiturates after flash-heater derivatization with dimethylformamide dimethylacetal.

Glass capillary column gas chromatography has been used for quantitative and qualitative analyses of barbiturates. The barbiturates are first converted into the corresponding acetal derivates by flash-heater derivatization, using dimethylformamide dimethylacetal as the derivatization reagent. The influence of the injection port temperature, the column temperature, the solvent used to dissolve the substances and the reagent dilution were studied in order to obtain the optimal response with good reproducibility. Calibration graphs in the concentration range 5--50 micrograms/ml were evaluated and the relative standard deviations for the quantitative analyses were calculated. High sensitivity was obtained when extracts from plasma containing phenobarbital in the low therapeutic concentration range were analysed using the described derivatization technique.

Barbiturates↗

PubMed2003

Electrochemical and spectroelectrochemical studies on UO(2)(saloph)L (saloph = N,N'-disalicylidene-o-phenylenediaminate, L=dimethyl sulfoxide or N,N-dimethylformamide).

To examine properties of pentavalent uranium, U(V), we have carried out electrochemical and spectroelectrochemical studies on UO(2)(saloph)L [saloph = N,N'-disalicylidene-o-phenylenediaminate, L = dimethyl sulfoxide (DMSO) or N,N-dimethylformamide (DMF)]. The electrochemical reactions of UO(2)(saloph)L complexes in L were found to occur quasireversibly. The reduction processes of UO(2)(saloph)L complexes were followed spectroelectrochemically by using an optical transparent thin layer electrode cell. It was found that the absorption spectra measured at the applied potentials from 0 to -1.650 V versus ferrocene/ferrocenium ion redox couple (Fc/Fc(+)) for UO(2)(saloph)DMSO in DMSO have clear isosbestic points and that the evaluated electron stoichiometry equals 1.08. These results indicate that the reduction product of UO(2)(saloph)DMSO is [U(V)O(2)(saloph)DMSO](-), which is considerably stable in DMSO. Furthermore, it was clarified that the absorption spectrum of the [U(V)O(2)(saloph)DMSO](-) complex has a very small molar absorptivity in the visible region and characteristic absorption bands due to the 5f(1) orbital at around 750 and 900 nm. For UO(2)(saloph)DMF in DMF, the clear isosbestic points were not observed in the similar spectral changes. It is proposed that the UO(2)(saloph)DMF complex is reduced to [U(V)O(2)(saloph)DMF](-) accompanied by the dissociation of DMF as a successive reaction. The formal redox potentials of UO(2)(saloph)L in L (E(0), vs Fc/Fc(+)) for U(VI)/U(V) couple were determined to be -1.550 V for L = DMSO and -1.626 V for L = DMF.

Journal Article↗

PubMed1999

Anti-Inflammatory Dinuclear Copper(II) Complexes with Indomethacin. Synthesis, Magnetism and EPR Spectroscopy. Crystal Structure of the N,N-Dimethylformamide Adduct.

Veterinary anti-inflammatory Cu(II) complexes of indomethacin (1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1H-indole-3-acetic acid = IndoH), of the general formula [Cu(2)(Indo)(4)L(2)] (L = N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), N-methylpyrrolidone (NMP), and water), were studied by zero-field and X-band EPR spectroscopies, electronic spectroscopy, magnetic measurements, and X-ray powder diffraction. The complexes are similar to Cu(II) acetate monohydrate, with a strong antiferromagnetic exchange interaction, J, ranging from -141 to -152 cm(-)(1). Variable temperature magnetic susceptibility data for all of the complexes are similar, with the exception of a [Cu(2)(Indo)(4)(H(2)O)(2)] complex, which displays an unusual increase in magnetic moment with decreasing temperature from 50 to 10 K. The X-ray powder diffraction patterns of the DMF and DMA dimers show that they are isostructural. Two isostructural H(2)O complexes were synthesized from different methods yet displayed different variable temperature magnetic susceptibity data. All of the [Cu(2)(Indo)(4)L(2)] complexes crystallize in the triclinic space group P&onemacr;. Single-crystal X-ray diffraction analysis of the DMF complex, [Cu(2)(Indo)(4)(DMF)(2)].1.6(DMF), shows that it is similar to the previously reported [Cu(2)(Indo)(4)(DMSO)(2)] with a Cu-Cu bond length of 2.630(1) Å, Cu-O(RCOO) of 1.960(4)-1.967(4) Å, and Cu-O(DMF) of 2.143(5) Å and crystal parameters a = 10.848(3) Å, b = 13.336(6) Å, c = 16.457(4) Å, alpha = 104.67(3) degrees, beta = 100.94(2) degrees, and gamma = 107.16(3) degrees. The X-ray structure of the DMF dimer does not exhibit strong intermolecular interactions due to the hydrophobic nature of the exterior. This may be important in facilitating its dissolution in micelles and transport through membranes.

Journal Article↗

PubMed2000

Kinetics and mechanism of complex formation of nickel(II) with tetra-N-alkylated cyclam in N,N-dimethylformamide (DMF): comparative study on the reactivity and solvent exchange of the species Ni(DMF)6(2+) and Ni(DMF)5Cl+.

13C NMR was used to study the rate of DMF exchange in the nickel(II) cation Ni(DMF)6(2+) and in the monochloro species Ni(DMF)5Cl+ with 13C-labeled DMF in the temperature range of 193-395 K in DMF (DMF = N,N-dimethylformamide). The kinetic parameters for solvent exchange are kex = (3.7 +/- 0.4) x 10(3) s-1, delta H++ = 59.3 +/- 5 kJ mol-1, and delta S++ = +22.3 +/- 14 J mol-1 K-1 for Ni(DMF)6(2+) and kex = (5.3 +/- 1) x 10(5) s-1, delta H++ = 42.4 +/- 4 kJ mol-1, and delta S++ = +6.7 +/- 15 J mol-1 K-1 for Ni(DMF)5Cl+. Multiwavelength stopped-flow spectrophotometry was used to study the kinetics of complex formation of the cation Ni(DMF)6(2+) and of the 100-fold more labile cation Ni(DMF)5Cl+ with TMC (1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) and TEC (1,4,8,11-tetraethyl-1,4,8,11-tetraazacyclotetradecane) in DMF at 298 K and I = 0.6 M (tetra-n-butylammoniumperchlorate). Equilibrium constants K for the addition of the nucleophiles DMF, Cl-, and Br- to the complexes Ni(TMC)2+ and Ni(TEC)2+ were determined by spectrophotometric titration. Formation of the complexes Ni(TMC)2+ and Ni(TEC)2+ was found to occur in two stages. In the initial stage, fast, second-order nickel incorporation with rate constants k1(TMC) = 99 +/- 5 M-1 s-1 and k1 (TEC) = 235 +/- 12 M-1 s-1 leads to the intermediates Ni(TMC)int2+ and Ni(TEC)int2+, which have N4-coordinated nickel. In the second stage, these intermediates rearrange slowly to form the stereochemically most stable configuration. First-order rate constants for the one-step rearrangement of Ni(TMC)int2+ and the two-step rearrangment of Ni(TEC)int2+ are presented. Because of the rapid formation of Ni(DMF)5Cl+, the reactions of Ni(DMF)6(2+) with TMC and TEC are accelerated upon the addition of tetra-n-butylammoniumchloride (TBACl) and lead to the complexes Ni(TMC)Cl+ and Ni(TEC)Cl+, respectively. For initial concentrations such that [TBACl]o/[nickel]o > or = 20, intermediate formation is 230 times (TMC) and 47 times (TEC) faster than in the absence of chloride. The mechanism of complex formation is discussed.

Journal Article↗

PubMed2003

Photoinduced magnetization of the cyano-bridged 3d-4f heterobimetallic assembly Nd(DMF)(4)(H(2)O)(3)(micro-CN)Fe(CN)(5).H(2)O (DMF = N,N-dimethylformamide).

Photoinduced magnetization of the cyano-bridged 3d-4f heterobimetallic assembly Nd(DMF)4(H2O)3(mu-CN)Fe(CN)5.H2O (1) (DMF = N,N-dimethylformamide) is described in this paper. The chiMT values are enhanced by about 45% after UV light illumination in the temperature range of 5-50 K. We propose that UV light illumination induces a structural distortion in 1. This small structural change is propagated by molecular interactions in the inorganic network. Furthermore, the cooperativity resulting from the molecular interaction functions to increase the activation energy of the relaxation processes, which makes observation of the photoexcited state possible. The flexible network structure through the hydrogen bonds in 1 plays an essential role for the photoinduced phenomenon. This finding may open up a new domain for developing the molecule-based magnetic materials.

Journal Article↗

PubMed2002

Dimethylformamide as a carbon monoxide source in fast palladium-catalyzed aminocarbonylations of aryl bromides.

Dimethylformamide (DMF) acts as an efficient source of carbon monoxide and dimethylamine in the palladium-catalyzed aminocarbonylation (Heck carbonylation) of p-tolyl bromide to provide the dimethylamide. Addition of amines to the reaction mixture in excess delivers the corresponding aryl amides in good yields. The amines employed, benzylamine, morpholine, and aniline, all constitute good reaction partners. The reaction proceeds smoothly with bromobenzene and more electron-rich aryl bromides, but electron-deficient aryl bromides fail to undergo aminocarbonylation. The reactions are conducted at 180-190 degrees C for 15-20 min with microwave heating in a reaction mixture containing imidazole and potassium tert-butoxide: the latter is required to promote decomposition of the DMF solvent at a suitable rate. The beneficial effects of controlled microwave irradiation as an energy source for the rapid heating of the carbonylation reaction mixture are demonstrated. The carbonylation procedure reported herein, which relies on the in situ generation of carbon monoxide, serves as a convenient alternative to other carbonylation methods and is particularly applicable to small-scale reactions where short reaction times are desired and the direct use of carbon monoxide gas is impractical.

Journal Article↗

PubMed2003

Electroreductive intramolecular cyclization of a bromo propargyloxy ester catalyzed by nickel(i) tetramethylcyclam electrogenerated at carbon cathodes in dimethylformamide.

Cyclic voltammetry and controlled-potential electrolysis have been employed to investigate and characterize the reductive intramolecular cyclization of ethyl 2-bromo-3-(3',4'-dimethoxyphenyl)-3-(propargyloxy)propanoate (1) promoted by (1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane)nickel(I), [Ni(tmc)](+), electrogenerated at glassy carbon cathodes in dimethylformamide containing tetraalkylammonium salts. Cyclic voltammograms for reduction of [Ni(tmc)](2+) in the presence of 1 reveal that [Ni(tmc)](+) catalytically reduces 1 at potentials more positive than those required for direct reduction of 1. During controlled-potential electrolyses of solutions containing [Ni(tmc)](2+) and 1, catalytic reduction of the latter proceeds via one-electron cleavage of the carbon-bromine bond to form a radical intermediate that undergoes cyclization to afford 2-(3',4'-dimethoxyphenyl)-3-(ethoxycarbonyl)-4-methylenetetrahydrofuran (2). In the presence of a base (either electrogenerated or deliberately added as potassium tert-butoxide), 2 rearranges to give 2-(3',4'-dimethoxyphenyl)-3-(ethoxycarbonyl)-4-methyl-2,5-dihydrofuran (3). A mechanistic scheme is proposed to explain the results obtained by means of cyclic voltammetry and controlled-potential electrolysis.

Journal Article↗

PubMed2006

Catalytic reduction and intramolecular cyclization of haloalkynes in the presence of nickel(I) salen electrogenerated at carbon cathodes in dimethylformamide.

[reaction: see text] Pentylidenecyclopentane can be conveniently prepared in up to 86% yield via the catalytic reduction of 1-iodo- or 1-bromo-5-decyne by [[2,2'-[1,2-ethanediylbis(nitrilomethylidyne)]bis[phenolato]]-N,N',O,O']nickelate(I) electrogenerated at a carbon cathode in dimethylformamide containing tetramethylammonium tetrafluoroborate. This electrosynthesis can be accomplished at potentials for which the haloalkynes are electroinactive, and it can be completed within 30 min at room temperature. Attempts to synthesize pentylidenecyclobutane and pentylidenecyclohexane from 1-halo-4-nonynes and 11-halo-5-undecynes, respectively, under similar conditions afford the carbocycles in very low yields (2% and 6%, respectively). Other products derived from the various haloalkynes are dimers, alkynes, and 1-alkenynes. Dimers (alkadiynes) arising from 1-halo-4-nonynes and 11-halo-5-undecynes are formed in yields ranging from 80% to 89%, whereas icosa-5,15-diyne (the dimer obtained from a 1-halo-5-decyne) is found in significantly lower yield (</=13%). Alkynes and 1-alkenynes are produced in yields of 3-10% and 2-3%, respectively. A mechanistic scheme, involving alkyn-1-yl radicals arising from nickel(I) salen catalyzed cleavage of the carbon-halogen bond of each haloalkyne, is proposed to account for the formation of all products.

Journal Article↗

PubMed1996

Electrochemical Reduction of Mono- and Dihalothiophenes at Carbon Cathodes in Dimethylformamide. First Example of an Electrolytically Induced Halogen Dance.

Cyclic voltammetry and controlled-potential electrolysis have been employed to probe the electrochemical reduction of a number of mono- and dihalothiophenes at carbon cathodes in dimethylformamide containing tetramethylammonium perchlorate. Reduction of 2-bromo-, 3-bromo-, 2-chloro-, 3-chloro-, and 2-iodothiophene gives rise to a single irreversible cyclic voltammetric wave for each compound that corresponds to the two-electron cleavage of the carbon-halogen bond, and thiophene is obtained as the only product. Cyclic voltammograms for the reduction of 2,3-dibromo-, 2,4-dibromo-, 2,5-dibromo-, 3,4-dibromo-, 2-bromo-5-chloro-, and 3-bromo-2-chlorothiophene each exhibit a pair of irreversible two-electron waves. Electrolyses of either 2,3-dibromo- or 2,4-dibromothiophene at potentials corresponding to the first voltammetric wave yield a two-to-one mixture of 3-bromo- and 3,4-dibromothiophene; under similar conditions, electrolyses of 2,5-dibromothiophene give a mixture of 2-bromo-, 3-bromo-, and 3,4-dibromothiophene, electrolyses of 2-bromo-5-chlorothiophene afford a mixture of 3-bromo-, 3,4-dibromo-, 3-bromo-2-chloro-, 4-bromo-2-chloro-, and 2-chlorothiophene, and electrolyses of 3-bromo-2-chlorothiophene yield 2-chlorothiophene. Aside from the last result, these product distributions appear to arise from an electrolytically induced halogen dance. When electrolyses of the dibromothiophenes and of 2-bromo-5-chloro- and 3-bromo-2-chlorothiophene are performed at potentials that correspond to the second voltammetric wave, thiophene is the only product obtained.

Journal Article↗

PubMed2005

Molecular dynamics of a polymer in mixed solvent: atactic polystyrene in a mixture of cyclohexane and N,N-dimethylformamide.

Local structural and dynamic properties of atactic polystyrene in a mixed solvent of cyclohexane (CH) and N,N-dimethylformamide (DMF) have been investigated using molecular dynamics simulations. We measure local conformations in the polymer and classify them by distance and angle distribution histograms. End-to-end distances and structure factors are employed to describe the static structure of polystyrene chains. Polystyrene concentration, including 1.6%, 4.8%, and 14% (by weight), and solution temperatures of 300, 330, or 360 K are used to elucidate the concentration and temperature dependencies of the solvation by the two solvents. Both solvent molecules preferentially approach the phenyl rings. At lower temperatures, polystyrene dissolves more favorably in cyclohexane. With rising temperature DMF molecules approach more closely with the oxygen oriented toward the phenyl rings. Additionally, the global and segmental relaxation times of the chains decrease and the system becomes more homogeneous. The segmental and global dynamics of polystyrene show different concentration behaviors: the reorientation times of solvent molecules and segments of polystyrene increase with concentration while the global dynamics of polystyrene decelerates as the concentration is changed from 1.6% to 4.8% but accelerates when the concentration rises to 14%. We conclude that the change of concentration from 4.8% to 14% qualitatively marks the change from a dilute to a semidilute solution. The diffusion constants of the small molecules and corresponding activation energies have also been measured. Our simulation data are compared with available experimental results and we find a satisfactory agreement.

Journal Article↗

PubMed2005

Anomalous green emission and energy transfer in the n,n-dimethylformamide/hydrochloric acid/europium chloride system.

The unusual green photoluminescence (PL) of N,N-dimethylformamide (DMF)/hydrochloric acid (HCl)/europium chloride (EuCl3) solutions discovered earlier was investigated in more detail to clarify the emission mechanism. It was revealed that the DMF/HCl pair alone can yield a green PL band under UV excitation, and the emission has features of that of excimers. The addition of EuCl3 salt to the solution further stimulates the green emission. The quantum yield of the line emission of Eu3+ ions at 592 and 612 nm is also affected by the presence of HCl in the solution. Both the green emission band and Eu3+ emission lines possess a common channel of excitation at approximately 280 nm. This channel is the only source for the green emission band and an additional source for the Eu3+ emission lines, which can also be stimulated through a conventional Eu3+ excitation channel at 394 nm. The common excitation channel was found to be time-dependent, and its excitation maximum gradually shifts to longer wavelengths. Changes in the PL profiles of europium ions were also observed depending on the presence of HCl and the solution aging.

Journal Article↗

PubMed2006

Liquid structure and preferential solvation of metal ions in solvent mixtures of N,N-dimethylformamide and N-methylformamide.

Raman spectra of aprotic N,N-dimethylformamide (DMF) and protic N-methylformamide (NMF) mixtures containing manganese(II), nickel(II), and zinc(II) perchlorate were obtained, and the individual solvation numbers around the metal ions were determined over the whole range of solvent compositions. Variation profiles of the individual solvation numbers with solvent composition showed no significant difference among the metal systems examined. In all of these metal systems, no preferential solvation occurs in mixtures with DMF mole fraction of x(DMF) < 0.5, whereas DMF preferentially solvates the metal ions at x(DMF) > 0.5. The liquid structure of the mixtures was also studied by means of small-angle neutron scattering (SANS) and low-frequency Raman spectroscopy. SANS experiments demonstrate that DMF molecules do not appreciably self-aggregate in the mixtures over the whole range of solvent composition. Low-frequency Raman spectroscopy suggests that DMF molecules are extensively hydrogen-bonded with NMF in NMF-rich mixtures, whereas NMF molecules extensively self-aggregate in DMF-rich mixtures, although the liquid structure in neat NMF is partly ruptured. The bulk solvent structure in the mixtures thus varies with solvent composition, which plays a decisive role in developing the varying profiles of the individual solvation numbers of metal ions in the solvent mixtures.

Journal Article↗

PubMed2006

Effects of intermolecular vibrational coupling and liquid dynamics on the polarized Raman and two-dimensional infrared spectral profiles of liquid N,N-dimethylformamide analyzed with a time-domain computational method.

A time-domain method for calculating polarized Raman and two-dimensional infrared (2D-IR) spectra that includes the effects of both the diagonal frequency modulations (of individual molecules in the system) and the off-diagonal (intermolecular) vibrational coupling is presented and applied to the case of the amide I band of liquid N,N-dimethylformamide. It is shown that the effect of the resonant off-diagonal vibrational coupling and the resulting delocalization of vibrational modes is clearly seen as the noncoincidence effect in the polarized Raman spectrum and some spectral features (especially as asymmetric intensity patterns) in the 2D-IR spectra. The type of 2D-IR spectra (concerning the polarization condition) most appropriate for observing this effect is discussed. On the basis of the agreement between the observed and calculated band profiles of the polarized Raman spectrum, the time dependence of the transient IR absorption anisotropy is also calculated. The method of evaluating the extent of delocalization of vibrational modes that is relevant to the features of these optical signals in the time and frequency domains is discussed. The nature of the molecular motions (concerning the liquid dynamics) that are effective on the diagonal frequency modulations is also examined.

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