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PubMed2006

Distribution of neutral organic compounds between n-heptane and methanol or N,N-dimethylformamide.

Partition coefficients for a number of varied compounds were determined for the n-heptane-methanol and n-heptane-DMF partition systems and used to derive a general model for the distribution of neutral compounds in the biphasic systems. The partition coefficient, log Kp, was correlated through the solvation parameter model giving log Kp = -0.056 + 0.164E-0.620S-1.337A-0.957B + 0.507V for the n-heptane-methanol system with a multiple correlation coefficient of 0.986, standard error of the estimate 0.086, and Fischer statistic 413 for 65 compounds. For n-heptane-DMF, the model is log Kp = 0.065 + 0.030E-1.405S-2.039A-0.806B + 0.721V with a multiple correlation coefficient of 0.991, standard error of the estimate 0.080, and Fischer statistic 560 for 59 compounds. In the models the solute descriptors are excess molar refraction E, dipolarity/polarizability S, overall hydrogen bond acidity, and basicity A and B, respectively, and McGowan's characteristic volume V. Either model is expected to be able to estimate further values of the partition coefficient to about 0.08 log units and is applicable to a wide range of compounds. Applications include the choice of partitioning systems for sample clean-up, countercurrent chromatography, and estimation of solute descriptors for water insoluble or unstable compounds.

Journal Article↗
PubMed2002

Analysis of problematic complexing behavior of ferric chloride with N,N-dimethylformamide using combined techniques of FT-IR, XPS, and TGA/DTG.

A problematic coordination behavior of highly hygroscopic FeCl(3) in DMF solution was studied. From the compositional and structural analyses for the adduct of FeCl(3)/DMF using various techniques such as FTIR, elemental analysis, UV/vis, XPS, and TGA/DTG, it was found that the iron cation exists in the form of an Fe(3+) cation and coordinates via the carbonyl oxygen atom of amide bond in DMF. The analyses of both FT-IR and XPS C 1s spectra for the adduct revealed that 2.1 molecules of DMF coordinate with a more electron-deficient Fe(3+); otherwise 1.2 molecules of DMF coordinated with a relatively electron-rich Fe(3+). The Cl 2p spectrum indicated that the electron-deficient Fe(3+) coordinated with two chlorine ions and the electron-rich Fe(3+) with four chlorines so that the chemical formula of the adduct is of [FeCl(2)(DMF)(1.2)(H(2)O)(2.7)](+)[FeCl(4)(DMF)(2.1)](-). The water molecules in the adduct were found chemisorbed rather than physisorbed, with a singular binding energy.

Journal Article↗
PubMed2003

Ferromagnetic ordering and metamagnetism in malonate bridged 3D diamond-like and honeycomb-like networks: [Cu(mal)(DMF)]n and [[Cu(mal)(0.5pyz)].H2O]n (mal = Malonate Dianion, DMF = N,N-dimethylformamide, pyz = Pyrazine).

Two three-dimensional (3D) malonate bridged networks, [Cu(mal)(DMF)](n) (1) and [[Cu(mal)(0.5pyz)].H(2)O](n) (2), have been synthesized in H(2)O-DMF solution. Compound 1 exhibits ferromagnetic ordering below 2.6 K (T(c)), and 2 displays a metamagnetic behavior below 3.2 K (T(N)).

Journal Article↗
PubMed2005

Electrochemistry of [(TMpyP)M(II)]4+ (X-)4 (X- = Cl- or BPh4-) and [(TMpyP)M(III)Cl]4+ (Cl-)4 in N,N-dimethylformamide where M is one of 15 different metal ions.

The electrochemistry of 16 different water-soluble porphyrins of the type [(TMpyP)M(II)]4+ (X-)4 or [(TMpyP)M(III)Cl]4+ (Cl-)4 is reported in nonaqueous media where TMpyP is the dianion of meso-tetrakis(N-methylpyridiniumyl)porphyrin and X- = Cl- or BPh4-. These studies were carried out to examine the effect of the metal ion and porphyrin counterion (X-) on the electrochemical properties of the TMpyP complexes with a special emphasis being given to the overall number of electrons added and the number of electrode processes upon reduction. All of the investigated compounds with electroinactive central metal ions undergo an overall addition of six electrons. This occurs for most compounds via three two-electron-transfer steps, but more than three processes are observed for porphyrins having metal ions with a low electronegativity (e.g., Cd(II)). The first reduction of each porphyrin having an M(II) ion or an electroinactive M(III) ion yields a porphyrin dianion which is characterized by an intense band located close to 800 nm, and this reversible reduction is followed by further reductions of the 1-methyl-4-pyridyl groups at more negative potentials. Four of the compounds with electroactive central metal ions, [(TMpyP)M(III)Cl]4+(Cl-)4 (M = Co, Fe, Mn, or Au), undergo an additional reversible M(III)/M(II) process prior to reactions involving the porphyrin pi-ring system and the 1-methyl-4-pyridyl substituents.

Journal Article↗
PubMed2002

Lewis base-promoted aldol reaction of dimethylsilyl enolates in aqueous dimethylformamide: use of calcium chloride as a Lewis base catalyst.

In the presence of CaCl2, dimethylsilyl (DMS) enolates smoothly reacted with aldehydes under mild conditions to give aldol adducts in good to high yields. The catalytic activities of various metal and tetrabutylammonium salts have revealed that CaCl2 works as a Lewis base catalyst to activate DMS enolates. The CaCl2-promoted reaction proceeded even in the presence of water or in pure water. This catalytic system was applicable to the aldol reaction with aqueous aldehydes such as formalin.

Journal Article↗
PubMed2006

Tetraaqua(7-hydroxy-5-oxidoflavone-6-sulfonato-kappa2O4,O5)nickel(II) dimethylformamide solvate monohydrate.

In the title compound, [Ni(C15H8O7S)(H2O)4].C3H7NO.H2O, the NiII cation is chelated by a 7-hydroxy-5-oxidoflavone-6-sulfonate ligand through one oxide and one carbonyl O atom, and the sixfold coordination is completed by four aqua ligands. Individual molecules are linked into hydrogen-bonded dimers by way of five pairs of O-H...O hydrogen bonds. These dimers, in turn, determine a three-dimensional supramolecular arrangement through a variety of interdimeric interactions, such as O-H...O, C-H...O and pi-pi stacking.

Crystallography, X-Ray↗