Bulletin of the Chemical Society of Japan

The title complex, [Co(odmbpc)], which is a single isomer and is highly soluble in common organic solvents, has been prepared and investigated electrochemically and spectroelectrochemically in dichloromethane solutions. The cyclic voltammograms of this complex at a concentration of ca. 6 × 10−5 mol dm−3 exhibited two reversible reduction waves at E1/2 = −0.67 V (vs. ferrocenium+/ ferrocene) and −1.74 V, which were attributed to cobalt-centered and triple-bond-centered (in a peripheral substituent) reductions, respectively, and three quasi-reversible oxidation waves at 0.26, 0.46, and 0.74 V, the former two and the latter one of which were attributed to phthalocyanine-chromophore-centered and cobalt-centered oxidations, respectively. Some of these assignments were supported by the electronic absorption spectra of the electro-generated species. The first reduction wave was not observed at 6 × 10−4 mol dm−3 until the applied potential was swept to the second reduction wave. Nevertheless, under the same conditions, the controlled-potential electrolyses in an optically transparent thin-layer electrode at potentials around the first reduction wave gave rise to drastic spectral changes without any preliminary electrolysis at potentials around the second reduction wave. Such strange phenomena are discussed in terms of molecular aggregation of the complexes in solutions. The peripheral alkynyl group has been found to be slightly electron-donating.

The effects of temperature and Zr concentration in solution on the composition and degree of crystallinity of zirconium phosphate have been examined. Pure θ-zirconium phosphate with an interlayer spacing of 10.4 Å has been prepared by direct precipitation.

The conditions for the synthesis of γ-NH4ZrH(PO4)2 and the ion-exchange properties of γ-Zr(HPO4)2·2H2O were investigated. The influence of the mole ratio of MH2PO4 (M=Na, K, and NH4) to ZrOCl2 on the formation of γ-zirconium phosphate using NaH2PO4 as MH2PO4 was such that the γ-form was obtained not in the NaH2PO4/ZrOCl2 mole ratio of 4, but in are of 8.3 or more. In case of the Na or K salt, a non-stoichiometric compound, MxZrH2−x(PO4)2, was obtained. When using the NH4 salt, a stoichiometric compound was synthesized at 120–280 °C in accordance with the following equation: ZrOCl2+NH4H2PO4→NH4ZrH(PO4)2+NH4Cl+HCl+H2O. Using an autoclave lined with Hastelloy-B and equipped with a stirrer, the synthesis was carried out by a reaction at 150–160 °C for 18–54 h. γ-Zr(HPO4)2·2H2O was prepared from NH4ZrH(PO4)2, and its ion-exchange capacity at pH 4.5 and selectivity quotient toward alkali metals and ammonium ions were measured. The measured values increased in the order of Li+<Cs+<Na+<K+<NH4+.

The direct-precipitation method was studied as a possible way to synthesize crystalline zirconium phosphate of a large and uniform crystal size. The yield and the crystal size were examined as functions of the initial hydrofluoric-acid and phosphoric-acid concentrations and the warming temperature. The conditions for preparing the largest crystal were: ZrOCl2·8H2O, 0.13 M; hydrofluoric acid concentration, 0.715 M; phosphoric acid concentration, 5 M; temperature, 50 °C. Those for preparing the material with uniform crystal-size distribution and a possibly large-mean crystal size were: ZrOCl2·8H2O, 0.13 M; hydrofluoric acid concentration, 0.715 M; phosphoric acid concentration, 9 M; temperature, 60 °C. The product was confirmed to be crystalline Zr(HPO4)2·H2O by means of chemical, thermal, and X-ray analyses, and by an examination of the titration curve.

The crystal structure of creatine monohydrate has been refined from three-dimensional X-ray data. This refinement introduces minor modifications to the positional and thermal parameters and confirmed the zwitter ion structure.

The reaction of various phenols with 2-ethoxy-1,3-dithiolane proceeded smoothly in the presence of BF3·Et2O to afford 1,3-dithiolan-2-ylated phenols, which were readily hydrolyzed to the corresponding aldehydes. This process was also extended to N,N-dimethylaniline and indole.

The synthesis of isoflavone derivatives by means of palladium-catalyzed cross-coupling reaction between 3-bromochromones and arylboronic acids or its butyl esters is described.

The interaction of a number of cationic dyes (I) with a varying number of methylene groups (Cn) in the alkyl chain attached to pyridyl nitrogen with a cationic surfactant (CTAB) assembly is reported. The binding constant of the dyes (C5 to C18) with the micelle have been calculated, and are found to increase with increasing carbon chain. A plot of the binding constant vs. the chain length shows a curve with a maximum for C16, which is attributed to a compatibility factor. From studies of the electronic and emission spectra it is proposed that a micelle has a hydrophobic force field and that the dyes are localized in various pockets of the field.

The thermal behavior of five complexes, [Co(NH3)6]Cl3 (1), [Co(NH3)5NO2]Cl2 (2), [Co(NH3)5NO]Cl2 (3), [(NH3)5Co–N(O)–NO–Co(NH3)5]Cl4·2H2O (4), and [(NH3)5Co–NO–ON–Co(NH3)5]Cl4·4H2O (5), has been investigated. The pyrolysis-gaschromatographic technique has been successfully applied to the N2- and N2O analyses of the gases evolved on the pyrolysis of the complexes. The thermal decomposition of these complexes is characterized predominantly by the reduction process of Co(III) to Co(II). In the simple nitrosyl 3, the NO− group reduces the Co(III) ion and dissociates as NO. As for the remaining complexes, a thermally induced transient-state tends to dissociate H+ from the coordinated ammonia as follows : CoIII–NH3→[CoIII–NH2δ−···Hδ+]→CoII+NH2+H+. The NH2 species is subsequently decomposed as NH2→2/3NH3+1/6N2. Moreover, H+ is captured by an anionic species and/or the NH3 present in the system, that is, by Cl− and NH3 forming NH4Cl in the case of 1, by NO2− and NH3 forming NH4NO2, which then decomposes to N2 and H2O, in 2, and by N2O22− forming H2N2O2, which then decomposes to N2O and H2O, in 4. The 5 complex undergoes an exothermic decomposition, affording a larger amount of N2 and N2O than those to be expected from the above stoichiometry, suggesting an oxidative behavior of the bridged, dimeric (–NO–ON–)2− group towards ammonia.