Bulletin of the Chemical Society of Japan

Ogumi, Zempachi; Mizoe, Toshiyuki; Zhen, Chen; Takehara, Zen-ichiro

doi: 10.1246/bcsj.63.3365pmid: N/A

The electrochemical behavior of a manganese redox couple incorporated into an SPE (Solid Polymer Electrolyte) composite electrode using Nafion (Pt–Nafion) was examined as a mediator for electroorganic syntheses. The mediatory reaction of the redox couple was examined in the oxidation of cinnamyl alcohol. The oxidation proceeded smoothly and gave cinnamaldehyde in high selectivity; the current efficiency was as high as 85%. The dissolving-out of manganese from the SPE was suppressed by the addition of 0.025 mol dm−3 MnSO4 to the catholyte.

Suga, Kosaku; Fujita, Shigeru; Yamada, Hiroshi; Fujihira, Masamichi

doi: 10.1246/bcsj.63.3369pmid: N/A

The rate constants of intramolecular photoinduced electron-transfer reactions of a linked pyrene–viologen molecule A and a linked pyrene–ferrocene molecule B solubilized in micellar solutions of a hexadecyltrimethylammonium chloride were determined to be 9×108 and 4×108 s−1 respectively, from the stationary fluorescence intensity. However, the observed fluorescence decay curve of A suggests that a large fraction of the molecules have conformations for which the distances between two functional moieties are sufficiently small to permit direct electron transfer. The quasi-first-order rate constants of the intermolecular photoinduced electron-transfer reactions between 1-hexylpyrene (HPy) and dodecylviologen (DDV), and between HPy and butylferrocene (BFc) solubilized in a micellar solution, were also determined to be 9×106 and 2×107 s−1 respectively, from the fluorescence decay curves. It is shown that the rate constants of the intermolecular photoinduced electron-transfer reaction in micelles are determined by the diffusion of the reactants in a micelle. On the other hand, it is suggested that the rate constants of the intramolecular electron-transfer reactions are determined by the molecular conformations of the linked compounds in micelles.

Uedaira, Hisashi; Ishimura, Miyuki; Tsuda, Sakae; Uedaira, Hatsuho

doi: 10.1246/bcsj.63.3376pmid: N/A

The spin-lattice relaxation times, T1, of H217O have been measured for aqueous solutions of 2 di-, 2 trisaccharides, α-, and γ-c clodextrins as a function of the concentration at 25°C. The dynamic hydration numbers, nDHN, for 17 sugars including monosaccharides were expressed by the linear relation of the mean number of the equatorial OH groups. The second virial coefficients showed a good correlation with nDHN. Though the rotational correlation times, τch, of water molecules in the cosphere of sugar molecules increased with increasing the number of equatorial OH groups for monosaccharides, those for trisaccharides and cyclodextrins showed almost constant values. The relation between the values of the limiting diffusion coefficients and nDHN for sugars was found to be expressed by two lines with a large negative slope for mono- and di- saccharides, and a small negative slope for trisaccharides and cyclodextrins.

Miyoshi, Hirokazu; Nippa, Satoru; Uchida, Hiroyuki; Mori, Hirotaro; Yoneyama, Hiroshi

doi: 10.1246/bcsj.63.3380pmid: N/A

TiO2 microcrystallites of different sizes were prepared in Nafion and the energy diagrams of these were determined from the onset potential of photocurrents due to oxidation of tartrate ions and the bandgap energy which was estimated from absorption spectra. The smallest particle prepared in the present study had the diameter less than 2 nm and the bandgap energy of 3.95 eV. Photocatalytic activities of the TiO2 microcrystallites prepared in Nafion for photodecomposition of acetic acid were very low compared to those of TiO2 microcrystallites prepared in clay interlayers and were comparable to those of the latter photocatalysts obtained in the presence of SO42−, suggesting that sulfonate groups of Nafion made the photocatalytic activity of TiO2 microcrystallites decrease.

Miyasaka, Hiroshi; Morita, Kazuhiro; Kamada, Kenji; Mataga, Noboru

doi: 10.1246/bcsj.63.3385pmid: N/A

Photoreduction processes of excited benzophenone (BP) by N,N-dimethylaniline (DMA) in acetonitrile solution were studied by means of picosecond-femtosecond laser photolysis and time resolved transient absorption spectroscopy as well as transient photoconductivity measurement. Proton transfer process in the triplet ion pair formed by electron transfer (ET) at encounter between 3BP* and DMA, competing with the ionic dissociation process was observed. It was clearly demonstrated that, in addition to the triplet ion pair, the ion pair produced by the excitation of the CT complex between BP and DMA formed in the ground state and that produced by ET reaction between 1BP* and DMA played important roles in the reaction processes of excited benzophenone. The behaviors of the three kinds of ion pairs were investigated in detail, leading to the elucidation of reaction mechanism of each ion pair. The reactivity characteristic of each kind of the ion pair and its relation to the structure of the ion pair were discussed.

Kohata, Katsunori; Kawamonzen, Yoshiaki; Odashima, Tsugikatsu; Ishii, Hajime

doi: 10.1246/bcsj.63.3398pmid: N/A

Four new water-soluble hydrazones, α-(5-nitro-2-pyridyl)hydrazono-α-(2-quinolyl)-3-toluenesulfonic acid, α-(5-nitro-2-pyridyl)hydrazono-α-(2-thiazolyl)-3-toluenesulfonic acid, α-(2-benzothiazolyl)-α-(5-nitro-2-pyridyl)hydrazono-3-toluenesulfonic acid, and α-(2-benzimidazolyl)-α-(5-nitro-2-pyridyl)hydrazono-3-toluenesulfonic acid, were synthesized. Their proton dissociation constants were determined spectrophotometrically. The chromogenic properties of the synthesized hydrazones and their reactions with metal ions were investigated spectrophotometrically in detail. The results revealed that the synthesized hydrazones react with various metal ions including transition metal ions, especially with cadmium(II), nickel(II), and zinc(II) to form stable colored complexes with very large apparent molar absorptivities, so that they were found to be all very useful as highly sensitive spectrophotometric reagents.

Ishii, Hajime; Odashima, Tsugikatsu; Kawamonzen, Yoshiaki

doi: 10.1246/bcsj.63.3405pmid: N/A

The complexation reaction of four water-soluble hydrazones, α-(5-nitro-2-pyridyl)hydrazono-α-(2-quinolyl)-3-toluenesulfonic acid (NPHQTS), α-(5-nitro-2-pyridyl)hydrazono-α-(2-thiazolyl)-3-toluenesulfonic acid (NPHTTS), α-(2-benzothiazolyl)-α-(5-nitro-2-pyridyl)hydrazono-3-toluenesulfonic acid (BTNPHTS) and α-(2-benzimidazolyl)-α-(5-nitro-2-pyridyl)hydrazono-3-toluenesulfonic acid (BINPHTS), with nickel(II) has been studied spectrophotometrically. These hydrazones react with nickel(II) to form a stable 1:2 (metal: ligand) complexes with high molar absorptivities. A sensitive and selective spectrophotometric method for the determination of nickel with BINPHTS has been developed. The nickel–BINPHTS complex is formed quantitatively in the pH range 6.5–8.9 and its absorption spectrum shows a maximum at 498 nm. Beer’s law is obeyed over the range 0.02–0.8 μg cm−3 of nickel and the apparent molar absorptivity of the complex is 8.67×104 dm3mol−1cm−1 at 498 nm. The proposed method was applied to the determination of nickel in manganese nodule samples, satisfactory results being obtained. Furthermore, the overall formation constants of nickel complexes of the four hydrazones were also determined spectrophotometrically.

Tsuchimoto, Masanobu; Kita, Masakazu; Fujita, Junnosuke

doi: 10.1246/bcsj.63.3410pmid: N/A

The electronic spectra of trans-[CoCl2(NH3)4]Cl and its analogues measured in the solid state at 113 K show four ligand field bands assignable to the Ia(1Ega← 1A1g), Ib(1A2g← 1A1g), IIa(1B2g← 1A1g), and IIb(1Egb← 1A1g) transitions in D4h approximation. The ligand field parameters obtained from the observed data are; eσ(N)=7400–8000 cm−1, eσ(Cl)=4500–5400 cm−1, eπ(Cl)=300–830 cm−1, and the Racah’s parameter C estimated with the assumption of C=4B is ca. 2000 cm−1. A nearly linear relationship is obtained between the eσ(Cl) and eπ(Cl) values; the stronger the coordination of Cl− to Co(III), the stronger the π interaction of Cl− with Co(III).

Kawata, Satoshi; Yokoi, Hiroshi; Iwaizumi, Masamoto

doi: 10.1246/bcsj.63.3414pmid: N/A

Binuclear copper(II) complexes of 3,12-bis(carboxymethyl)-6,9-dioxa-3,12-diazatetradecanedioic acid have been investigated by EPR. It has been confirmed that three different binuclear complexes are formed, depending on the pH of the solution. The complex formed in the low pH region has a copper–copper distance of 5.5 Å and a weak magnetic dipolar interaction. The other two are of olated forms with strong magnetic interactions between the copper atoms through oxygen bridges. One of them has an antiferromagnetic interaction; though the other has a weak antiferromagnetic interaction, it shows a large zero-field splitting. Such differences between the magnetic properties of the two olated complexes are attributed to a difference in the bridged style, i.e., the former is a mono-μ-hydroxo-bridged complex and the latter is a double-μ-hydroxobridged complex.

Radnai, Tamas; Inoue, Kenta; Ohtaki, Hitoshi

doi: 10.1246/bcsj.63.3420pmid: N/A

The structures of mono(α-alaninato)zinc(Il), bis(α-alaninato)zinc(II), and tris(α-alaninato)zincate(II) complexes in aqueous solutions were determined by the X-ray diffraction method. All the three complexes have the octahedral structure in the form [Zn(α-ala)(H2O)4]+, [Zn(α-ala)2(H2O)2], and [Zn(α-ala)3]−. The structures of the complexes were different from those of the glycinato complexes of zinc(II) ion, which were all regular octahedral. The length of the Zn–O bond in the α-alaninato complexes was shorter than that of the Zn–N bond due to the inductive effect of the substituted methyl group at the α-carbon on the oxygen atom in the amino acid. The lengths of the Zn–O and Zn–N bonds in the complexes determined are, respectively, as follows: [Zn(α-ala)(H2O)4]+, 202 and 214 pm; [Zn(α-ala)2(H2O)2], 203 and 214 pm; [Zn(α-ala)3]−, 202 and 213 pm.