Showing papers by "Hiroshi Nishihara published in 1994"

A Chemical Modification of Alkanethiol Self‐Assembled Monolayers with Alkyltrichlorosilanes for the Protection of Copper Against Corrosion

Abstract: A self-assembled monolayer of 11-mercapto-1-undecanol chemisorbed on the copper surface was chemically modified by reactions of the monolayer with alkyltrichorosilane and water to form alkylsiloxane polymer in the film. The alkylsiloxane modified monolayers were characterized by x-ray photoelectron (XPS) and Fourier transform infrared reflection spectroscopies (FTIRAS) and impedance, polarization, and contact angle measurements. A structure of the cross-linked alkylsiloxane modified layer adsorbed on the copper surface was confirmed by XPS and FTIRAS

Synthesis and Reactions of Monosilylated 1,3,5-Hexatriyne and 1,3,5,7-Octatetrayne. Total Synthesis of Caryoynencins.

Abstract: Selective monodesilylation of 1,8-bis(t-butyldiphenylsilyl)-1,3,5,7-octatetrayne and 1,6-bis(t-butyldiphenylsilyl)-1,3,5-hexatriyne with lithiated phenylacetylene gave unstable 1-(t-butyldiphenylsi...

Composite Film Formation on Iron in Sulfuric Acid by Bismuth(III) Chloride and Benzyl Thiocyanate

Abstract: A synergistic inhibitory effect of bismuth(III) chloride (BiIIICl3) and benzyl thiocyanate (C6H5CH2SCN) on corrosion of iron (Fe) in 1 N sulfuric acid (H2SO4) was investigated using polari...

Electrochemical synthesis of soluble poly(9-hexylfluorene) and poly(1-hexylindene)

Abstract: Electrochemical oxidation of 9-hexylfluorene and 1-hexylindene in 0.1 mol dm–3 Bu4NBF4–nitromethane affords π-conjugated polymers, PHF and PHI, respectively, which are fusible and soluble in common organic solvents. Electrode materials affect the formation of the polymers significantly; the molecular weight of PHF increases in the order, glassy carbon (GC) < indium–tin oxide (ITO)⩽ SnO2, and that for PHI, SnO2 GC < ITO. 1 H NMR and IR spectra of the polymers indicate that PHF and PHI comprise mainly linkage of 1,4-fluorenylene and 2, 4-indenylene units, respectively. PHF undergoes a reversible oxidation reaction in acetonitrile, whereas electrochemical oxidation of PHI is irreversible. The electrical conductivities of PHF and PHI doped with SO3 are 10–5 and 10–6 S cm–1, respectively, at room temperature.

Synthesis of soluble cobaltacyclopentadiene oligomers and polymers

Abstract: Summary form only given. Transition metal complex polymers involving highly and linearly /spl pi/-conjugated organic moieties have a possibility to show novel physical and chemical properties based on electronic interaction between /spl pi/-electrons (orbitals) and d-orbitals (electrons). Our previous study has shown that successive addition reaction of 4,4'-diethynylbiphenyl to CoCp(PPh/sub 3/)/sub 2/] gives a /spl pi/-conjugated organometallic polymer, poly(4,4'-biphenylene 2,5-cobaltacyclopenta-2,4-dienylene) as an insoluble material. We report here a study on the synthesis of soluble cobaltacyclopentadiene oligomers and polymers. The soluble oligomers and polymers, HC/spl equiv/C-C/sub 6/H/sub 4/{C/sub 4/H/sub 2/[Co(hexyl-Cp)(PPh/sub 3/)]-C/sub 6/H/sub 4/}nC/spl equiv/CH, were obtained by a reaction of [Co(hexyl-Cp)(PPh/sub 3/)/sub 2/] with p-diethynylbenzene. The n-hexyl group introduced in Cp ring increases the solubility of the polymers in common organic solvents such as toluene. The products were separated with a recycling preparative HPLC apparatus into several oligomers and a polymer. Characterization and electrochemical properties of the products will be reported.

Corrosion Inhibition of Cobalt in Some Acid Solutions by Bismuth(III) Chloride

Abstract: Inhibition effects of bismuth(III) chloride on cobalt corrosion in 1N HClO[sub 4], 1N H[sub 2]SO[sub 4], and 1N HCl were investigated by polarization measurements and colorimetry of dissolved cobalt ion. More than 85% of the inhibition efficiency was obtained for cobalt in these acid solutions. X-ray photoelectron spectra showed the formation of a protective film which comprises an inner layer composed of metallic bismuth and an outer layer of cobalt(II), bismuth(III), chloride, oxide, and hydroxide ions. Because the cathodic bismuth deposition was stimulated and a uniform layer of bismuth was not formed on the surface, the corrosion reaction was accelerated in 1N HClO[sub 4] at a high concentration of the inhibitor. The inhibition efficiency of the compound for various metals in 1N HClO[sub 4] was confirmed as being associated with a difference in the standard electrode potential between bismuth and a metal.

Effect of Formic Acid on Iron Corrosion in an Anhydrous Methanol Solution

Abstract: Such a protic acid as formic acid is possible to react with anhydrous methanol , Effect of the formic acid reaction with methanol on the corrosion rate of iron in an anhydrous methanol solution of 0.1M NaClO4 was investigated by cyclic voltammetry and impedance measurement, The corrosion rate was lowered as the concentration of formic acid decreased with an increase in the immersion time . The fomation of methyl formate and water by the reaction complicates the process of iron corrosion in the methanol solution.

Synthesis and physical properties of transition metal complexes of poly(9-n-hexylfluorene) and poly(l-n-hexylindene)

Abstract: Summary form only given. Polyfluorene and polyindene are /spl pi/-conjugated organic polymers with both /spl eta/sub 5// - or /spl eta/sub 6// /spl pi/-coordination abilities to transition metal centers. It is interesting to understand how the electrical, optical and magnetic properties of the /spl pi/-conjugated systems in such polymers can be perturbed by the electronic interaction with d-electrons (orbitals) of transition metals. We have previously reported the electrochemical synthesis of poly(9-n-hexylfluorene) (PHF) and poly(l-n-hexylindene) (PHI), which are soluble in less polar organic solvents such as benzene or dichloromethane and thus utilizable as reagents in homogeneous reactions. In this paper we present a study on the synthesis and physical properties of transition metal complexes of PHF and PHI. Reaction of PHF with Mn(CO)/sub 5/Br in the presence of AICl/sub 3/ gives PHF-Mn(CO)/sub 3/ where PHF behaves as /spl eta/sub 5//-ligands. PHF-Mn(CO)/sub 3/ shows a shift of absorption edge in the visible spectrum to the longer wavelength and an increase in electric conductivity compared to free PHF. Synthesis and physical properties of other polymer complexes, PHF-CO(C/sub 5/Me/sub 5/)/sup +/ and PHI-Rh(C/sub 5/Me/sub 5/)/sup +/ will be also reported.

The Inhibitive Effect of Organic Cations on Passive Film Breakdown of Iron in a Chloride-Containing Borate Buffer Solution.

Abstract: The inhibitive effect of an organic cation inhibitor, alkyltrimethylammonium ions on the passive film breakdown of an iron electrode in the borate buffer containing Cl − was investigated by polarization measurement and X-ray photo-electron spectroscopy. The pitting potential of a passivated iron electrode shifted in the positive direction following the addition of the inhibitor, indicating inhibition of the breakdown. Since X-ray photo-electron spectra showed the absence of Cl − in the passive film near the iron substrate, it is concluded that the cation inhibitor suppresses migration of Cl − into the passive film via an electrostatic interaction between the adsorbed Cl − and the cation at the film surface. The inhibitive effect of alkyltrimethylammonium ion increased and then decreased with an increase in the carbon number of an alkyl chain. The increase of the effect is attributed to coverage of the passive film surface with the cation inhibitor to hinder adsorption of Cl − and the decrease is ascribed to lowering of the film thickness and the borate ion content in the film.

Corrosion Inhibition of Cobalt in Some Acid Solutions by Bismuth(III) Chloride.

Abstract: Inhibition effects of bismuth(III) chloride on cobalt corrosion in 1N HClO[sub 4], 1N H[sub 2]SO[sub 4], and 1N HCl were investigated by polarization measurements and colorimetry of dissolved cobalt ion. More than 85% of the inhibition efficiency was obtained for cobalt in these acid solutions. X-ray photoelectron spectra showed the formation of a protective film which comprises an inner layer composed of metallic bismuth and an outer layer of cobalt(II), bismuth(III), chloride, oxide, and hydroxide ions. Because the cathodic bismuth deposition was stimulated and a uniform layer of bismuth was not formed on the surface, the corrosion reaction was accelerated in 1N HClO[sub 4] at a high concentration of the inhibitor. The inhibition efficiency of the compound for various metals in 1N HClO[sub 4] was confirmed as being associated with a difference in the standard electrode potential between bismuth and a metal.

Synthesis and Reactions of Monosilylated 1,3,5-Hexatriyne and 1,3,5,7- Octatetrayne. Total Synthesis of Caryoynencins.

Abstract: Selective monodesilylation of 1,8-bis(t-butyldiphenylsilyl)-1,3,5,7-octatetrayne and 1,6-bis(t-butyldiphenylsilyl)-1,3,5-hexatriyne with lithiated phenylacetylene gave unstable 1-(t-butyldiphenylsi...