Mössbauer study on characterization of Co[Fe(CN)5NH3 \cdot x H2O

The electronic states of Fe atoms in Co[Fe(CN)₅NH₃ H₂O were studied by means of ⁵⁷Fe Mössbauer spectroscopy. The Mössbauer spectra of Co[Fe(CN)₅NH₃ 6H₂O show the coexistence of mixed valences for the Fe atoms and a magnetic relaxation at 4 K. When water molecules were removed, electron transfer from Co to Fe occurred.     

Characterization of an NH-pi interaction in Co(III) ternary complexes with aromatic amino acids

The NH-pi interaction has been detected in the crystal structures of Co(III) ternary complexes with N,N-bis(carboxymethyl)-(S)-phenylalanine (BCMPA) and aromatic amino acids including (S)-phenylalanine ((S)-Phe), (R)-phenylalanine ((R)-Phe), and (S)-tryptophan ((S)-Trp)). Additionally, this interaction has been studied in solution for Co(III) ternary complexes with BCMPA or NTA (NTA = nitrilotriacetic acid) and several amino acids (AA) by means of electronic absorption, circular dichroism (CD), and (1)H NMR spectroscopies. The CD intensities of the Co(III) complexes with aromatic amino acids measured in the d-d region ( approximately 20.5 x 10(3) cm(-)(1)) are significantly decreased in ethanol solutions relative to water. Analogous complexes with aliphatic amino acids do not exhibit this solvent effect. The (1)H NMR spectra of the Co(III) complexes with aromatic amino acids measured in DMSO-d(6) exhibit upfield shifts of the NH peaks compared with those with aliphatic amino acids, which suggest a shielding effect due to the aromaticity. The upshift values coincide with those experimentally evaluated from the crystal structures. The magnitude of the upfield shifts agrees well with Hammett's rule, indicating that the increase of pi-electron densities on the aromatic rings leads attractive NH-pi interaction that exerts a larger shielding effect for the NH protons. In ligand-substitution reactions of the carbonatocobalt(III) complexes with amino acids, the yields of those with aromatic amino acids are higher than the yields obtained for complexes with aliphatic amino acids. This observation is discussed in connection with the important contribution of the NH-pi interaction as one of the promotion factors in the reaction.     

Structural and Spectroscopic Characterization of a Mononuclear Hydroperoxo–Copper(II) Complex with Tripodal Pyridylamine Ligands

A model for the key intermediate in copper oxygenase reactions, the Cu(II )–OOH complex, was prepared with the novel tripodal pyridylamine ligand, bis(6-pivalamide-2-pyridylmethyl)(2-pyridylmethyl)amine. The HOO⁻ moiety is stabilized by hydrogen bonding to two amine H atoms (see structure on the right).     

Sustainable Mizoroki-Heck reaction in water: remarkably high activity of Pd(OAc)2 immobilized on reversed phase silica gel with the aid of an ionic liquid

Palladium acetate immobilized on reversed phase amorphous silica gel with the aid of an ionic liquid, [bmim]PF6, was highly efficient in the promotion of the Mizoroki-Heck reaction in pure water without a ligand up to the sixth re-use, in 95% average yield with TON and TOF 1,600,000 and 71,000 (h(-1)), respectively.     

The onset of three-phase separation in ternary polymer solutions

A theoretical study is made of three-phase separation in a ternary solution consisting of a pure solvent and two homologous monodisperse polymers with relative chain lengths P₁ and P₂. The Flory—Huggins interaction parameter X is assumed to depend linearly on the volume fraction ? of the polymer mixture: χ = χ₀(T) + k(T)_?. For a given P₁ the ratio of P₂ to P₁ for the onset of three-phase separation increases with an increase in k, first gradually and then sharply. Loci of critical points for this condition on the χ₀ vs. ? diagram are determined for a series of fixed values of P₁ and their significance is discussed.     

Fließeigenschaften von Polymerlösungen. 2. Mitt. Phänomenologische Beziehungen für die Spannung nach dem plötzlichen Start des stationären Fließens unter Scherung

Ohne Zusammenfassung     

Electrochemical Oxidation Behavior of Nitrogen Dioxide for Gas Detection Using Boron Doped Diamond Electrodes

The electrochemical oxidation reaction of nitrogen dioxide (NO₂) using boron doped diamond (BDD) electrodes is presented. Cyclic voltammetry of NO₂ in a 0.1 M KClO₄ solution exhibits oxidation peaks at +1.1 V and +1.5 V (vs. Ag/AgCl) which are attributable to oxidation of HONO and NO₂⁻, respectively. Moreover, the pH and scan rate dependences were investigated to study the oxidation mechanism. A linear calibration curve was observed in the concentration range of ∼1 to 5 mM (R²=0.99) with a detection limit of 11.1 ppb (S/B=3) for HONO and 58.6 ppb (S/B=3) for NO₂⁻. In addition, the analytical performance was compared with those using glassy carbon, platinum and stainless steel as the working electrode.     

A New Family of Anionic FeIII Spin Crossover Complexes Featuring a Weak‐Field N2O4 Coordination Octahedron

Unprecedented anionic Fe^III spin crossover (SCO) complexes involving a weak‐field O,N,O‐tridentate ligand were discovered. The SCO transition was evidenced by the temperature variations in magnetic susceptibility, Mössbauer spectrum, and coordination structure. The DFT calculations suggested that larger coefficients on the azo group in the HOMO?1 of a ligand might contribute to the enhancement of a ligand‐field splitting energy. The present anionic SCO complex also exhibited the light‐ induced excited‐spin‐state trapping effect.     

Crystal-face-selective adsorption of Au nanoparticles onto polycrystalline diamond surfaces

Crystal-face-selective adsorption of Au nanoparticles (AuNPs) was achieved on polycrystalline boron-doped diamond (BDD) surface via the self-assembly method combined with a UV/ozone treatment. To the best of our knowledge, this is the first report of crystal-face-selective adsorption on an inorganic solid surface. Hydrogen-plasma-treated BDD samples and those followed by UV/ozone treatment for 2 min or longer showed almost no adsorption of AuNP after immersion in the AuNP solution prepared by the citrate reduction method. However, the samples treated by UV/ozone for 10 s showed AuNP adsorption on their (111) facets selectively after the immersion. Moreover, the sample treated with UV/ozone for 40-60 s showed AuNP adsorption on the whole surface. These results indicate that the AuNP adsorption behavior can be controlled by UV/ozone treatment time. This phenomenon was highly reproducible and was applied to a two-step adsorption method, where AuNPs from different batches were adsorbed on the (111) and (100) surface in this order. Our findings may be of great value for the fabrication of advanced nanoparticle-based functional materials via bottom-up approaches with simple macroscale procedures.