Bis(cyclopentadienyl)titanium complexes of naphthalene-1,8-dithiolates, biphenyl 2,2'-dithiolates, and related ligands

Titanocene 1,8-dithiolato-naphthalene and titanocene 2,2'-dithiolato biphenyl are produced by the reaction of naphtho[1,8-cd]-1,2-dithiole [or the biphenyl] with titanocene dicarbonyl (Ti(II)) in toluene at room temperature. The pro-ligands 2,7-di(tert-butyl)naphtho[1,8-cd]-1,2-dithiole, 5,6-dihydroacenaphtho[5,6-cd]-1,2-dithiole, 4,5-dithioacephenanthrylene, and 13,14-dithiapicene have been used in similar reactions with titanocene dicarbonyl to investigate the effect of steric bulk and of varying the naphthalene backbone on the final complex. The resulting Cp(2)TiS(2)Ar complexes (Ar = naphthalene) have been shown by temperature-dependent (1)H NMR spectroscopy to exist in solution in an envelope conformation with the six-membered TiS(2)C(3) rings undergoing inversion on the NMR time scale while the similar Cp(2)TiS(2)Ar complexes (Ar = biphenyl, binaphthalene) interconvert more rapidly. Titanocene 2,2'-disulfinato biphenyl has been synthesized by the salt elimination reaction of titanocene dichloride (Ti(IV)) and the disodium salt of biphenyl 2,2'-disulfinic acid. Finally, the effect of using pro-ligands where the sulfur atoms have been mono- or di-oxidized has been studied, and an interesting oxygen elimination reaction is observed for the S=O fragments but not for the SO(2) groups. All complexes have been characterized spectroscopically and seven X-ray structures are reported.     

Ruthenium-catalyzed propargylic substitution reactions of propargylic alcohols with oxygen-, nitrogen-, and phosphorus-centered nucleophiles

The scope and limitations of the ruthenium-catalyzed propargylic substitution reaction of propargylic alcohols with heteroatom-centered nucleophiles are presented. Oxygen-, nitrogen-, and phosphorus-centered nucleophiles such as alcohols, amines, amides, and phosphine oxide are available for this catalytic reaction. Only the thiolate-bridged diruthenium complexes can work as catalysts for this reaction. Results of some stoichiometric and catalytic reactions indicate that the catalytic propargylic substitution reaction proceeds via an allenylidene complex formed in situ, whereby the attack of nucleophiles to the allenylidene C(gamma) atom is a key step. Investigation of the relative rate constants for the reaction of propargylic alcohols with several para-substituted anilines reveals that the attack of anilines on the allenylidene C(gamma) atom is not involved in the rate-determining step and rather the acidity of conjugated anilines of an alkynyl complex, which is formed after the attack of aniline on the C(gamma) atom, is considered to be the most important factor to determine the rate of this catalytic reaction. The key point to promote this catalytic reaction by using the thiolate-bridged diruthenium complexes is considered to be the ease of the ligand exchange step between a vinylidene ligand on the diruthenium complexes and another propargylic alcohol in the catalytic cycle. The reason why only the thiolate-bridged diruthenium complexes promote the ligand exchange step more easily with respect to other monoruthenium complexes in this catalytic reaction should be that one Ru moiety, which is not involved in the allenylidene formation, works as an electron pool or a mobile ligand to another Ru site. The catalytic procedure presented here provides a versatile, direct, and one-step method for propargylic substitution of propargylic alcohols in contrast to the so far well-known stoichiometric and stepwise Nicholas reaction.     

Ultralow interfacial tension for enhanced oil recovery at very low surfactant concentrations

The interfacial tension (IFT) between alkanes and several individual surfactants and their mixtures has been investigated, using three kinds of alkyl hydrocarbons: decane, dodecane, and tetradecane. For individual and mixed surfactant systems, critical micelle concentrations and areas per molecule at the hydrocarbon-aqueous solution interface were calculated; for the mixed surfactant systems, betasigma(LL), the molecular interaction parameter at the hydrocarbon-aqueous solution interface, and beta(M), the molecular interaction parameter in mixed micelle formation, were calculated. It was found that IFT in the 10(-3) mN/m (ultralow) range can be obtained at surfactant concentrations below 0.05 wt % and even at concentrations below 0.01 wt %, when mixtures of certain surfactants are used at the proper ratio. Surfactants with branched-chain alkyl groups show a much better IFT reduction effectiveness than those with straight-chain alkyl groups. Contrary to what has been observed at the air-aqueous solution surface, mixtures of two homologues with two hydrophobic groups show significant molecular interactions, with both betasigma(LL) and beta(M) having negative values in the 4-5 range in some cases, with the betasigma(LL) value more negative than beta(M). The relationship between micellar shape and ultralow IFT was investigated by calculating the critical packing parameter of the surfactants. It was found that ultralow IFT between the surfactant mixtures and the three hydrocarbons investigated could reach ultralow (<10(-2) mN/m) values when the critical packing parameter is very close to 1.     

Direct determination of selenium in urine samples by electrothermal atomic absorption spectrometry using a Zr plus Rh-treated graphite tube and co-injection of Rh as chemical modifier

Different chemical modifiers for use with electrothermal atomic absorption spectrometry (ET AAS) were investigated in relation to determining the selenium in human urine samples. The samples were diluted in a solution containing 1% v/v HNO₃ and 0.02% m/v cetyltrimethylammonium chloride (CTAC). Studying the modifiers showed that the use of either Ru or Ir as the permanent modifier gave low sensitivity to Se and the peak shape was very noisy, while Zr or Rh gave no peak at all. The same occurred when Zr was used in solution. For mixtures of permanent modifiers, Ir plus Rh or Zr plus Rh gave very low sensitivity, Zr plus Rh with co-injection of Ir in solution was also not efficient, Zr plus Rh in solution gave good sensitivity, but the best results were obtained with a mixture of Zr and Rh as the permanent modifier and co-injection of Rh in solution. Using this last modifier, the following dilutions with the HNO₃ and CTAC were studied: 1:1, 1:2, 1:3 and 1:4. The best dilution was 1:1, which promoted good sensitivity and a more defined peak shape and made it possible to correct for the background using a deuterium arc lamp. Under these conditions, a characteristic mass of 26±0.2 pg was obtained for Se in aqueous solution. Six certified urine samples were analyzed using matrix matching calibration and the measured concentrations were in agreement with the certified values, according to a t-test at the 95% confidence level. Recovery tests were carried out and the recoveries were in the range 100–103%, with relative standard deviation better than 9%. The limit of detection (LOD, 3 sd, n=10) was 3.0 μg L⁻¹ in the sample. The treated graphite tube could be used for at least 600 atomization cycles without significant alteration of the analytical signal.     

The infrared spectra and theoretical calculations of frequencies of fac-tricarbonyl octahedral complexes of manganese(I)

The carbonyl stretching frequencies in the infrared spectra of 38 fac-tricarbonyl octahedral complexes of manganese(I) prepared in this laboratory were determined. These complexes may be grouped into three types: (a) neutral complexes of the structure (CO)(3)Mn(P-P)Z where P-P represents depe, dppe, or dppp, and Z represents various anionic functional groups bonded to the manganese; (b) ionic complexes of the structure [(CO)(3)Mn(P-P)Z](+)BF(4)(-) where Z represents various neutral molecules possessing one phosphorous, nitrogen, or oxygen atom coordinated to the manganese; (c) complexes of the structure (CO)(3)Mn(pn)Z where the chelating pn represents 1,1-diphenylphosphino-2,2-dimethylaminoethane, Ph(2)PCH(2)CH(2)NMe(2). All of these complexes show three carbonyl stretching modes (2A' + A"). The effects on the frequencies of these modes induced by both the various Z groups and the various ligands are discussed. Theoretical calculations (B3LYP/6-31G) with optimization of the full molecule make it possible to distinguish between the three stretching modes and to make unambiguous assignments of appropriate symmetry species to each.     

Structural effects on surface and micellar properties of alkanediyl-alpha, omega-bis(sodium N-acyl-beta-alaninate) gemini surfactants

A study of the equilibrium surface properties (in water and in the presence of 0.01 M NaCl) of a novel series of anionic gemini surfactants, alkanediyl-alpha,omega-bis(sodium N-acyl-beta-alaninates), is described. Parameters studied include cmc (critical micelle concentration), C20 (required to reduce the surface tension of the solvent by 20 mN/m), gamma(cmc) (the surface tension at the cmc), Gamma(max) (the maximum surface excess concentration at the air/aqueous solution interface), Amin (the minimum area per surfactant molecule at the air/water interface), and the cmc/C20 ratio (a measure of the tendency to form micelles relative to adsorb at the air/water interface). The geminis with a spacer consisting of two methylene groups show premicellar self-aggregation, both in water and in 0.01 M NaCl, when the N-acyl group contains more than 12 carbon atoms; geminis with a spacer consisting of four methylene groups show no premicellar aggregation even when the N-acyl group contains 16 carbon atoms. For the acyl chain lengths where premicellar aggregation does not occur, the values of the cmc of the geminis with a two-methylene spacer are lower than those for the corresponding analogous geminis with a four-methylene spacer. The premicellar formation for the geminis with a two-methylene spacer is due to the short-chain linkage. The geminis show little or no break in their specific conductance-surfactant molar concentration plots and an increase in the pH at the cmc. This is attributed to protonation of the carboxylate group and strong Na+ release during micellization.     

Synthesis of novel 4-amino-1,4-benzodiazepine-2,5-diones for anticonvulsant testing

A series of novel 4-amino-1,4-benzodiazepine-2,5-diones was synthesized via two pathways. The first method involved reductive alkylation of unsymmetrical hydrazines with glyoxylic acid, followed by Fisher esterification. The resulting N-aminoglycinate ethyl ester was subsequently o-nitrobenzoylated, reduced, and thermally cyclized to obtain 4-dialkylaminobenzodiazepinones. In the second method methylhydrazine was acetylated at N_α then benzoylated at N_β to give 1,2-diacylhydrazines. Alkylation with ethyl bromoacetate and reduction of the nitro group, followed by thermal cyclization yielded 4-acetamidobenzodiazepinones. All title compounds were evaluated in mice in MES seizure and sc Met seizure threshold tests for anticonvulsant activity, and in the rotorod test for neurotoxicity. Activity and toxicity were both minimal.     

Optical and Electrical Properties of Polymerizing Plasmas and Their Correlation with DLC Film Properties

Diamond-like carbon (DLC) films were grown from radiofrequency plasmas of acetylene-argon mixtures, at different excitation powers, P. The effects of this parameter on the plasma potential, electron density, electron temperature, and plasma activity were investigated using a Langmuir probe. The mean electron temperature increased from about 0.5 to about 7.0 eV while the mean electron density decreased from about 1.2 × 10⁹ to about 0.2 × 10⁹ cm^–3 as P was increased from 25 to 150 W. Both the plasma potential and the plasma activity were found to increase with increasing P. Through actinometric optical emission spectrometry, the relative concentrations of CH, [CH], and H, [H], in the discharge were mapped as a function of the applied power. A rise in [H] and a fall in [CH] with increasing P were observed and are discussed in relation to the plasma characteristics and the subimplantation model. The optical properties of the films were calculated from ultraviolet-visible spectroscopic data; the surface resistivity was measured by the two-point probe method. The optical gap, E _G, and the surface resistivity, _s, fall with increasing P. E _G and _s are in the ranges of about 2.0–1.3 eV and 10¹⁴–10¹⁶ /, respectively. The plasma power also influences the film self-bias, V _b, via a linear dependence, and the effect of V _b on ion bombardment during growth is addressed together with variation in the relative densities of sp² and sp³ bonds in the films as determined by Raman spectroscopy.