Spin orientation and excitation of magnetic nanocluster on metal surface

The spin orientation and excitation of the ferromagnetic nanocluster on the magnetic metal surface are studied numerically. We show that localized magnetic excitation modes are generated by the spin fluctuation of the cluster, when the ferromagnetic interaction J′ between the cluster and the metal surface is small and the spins in the cluster are oriented in the opposite direction with those of the metal surface by the external field. This magnetic structure is similar to the domain wall (DW) structure of a ferromagnetic wire, both sides of which connect with metal surfaces. As the interaction J′ increases, the sign of the thermal average of the spins in the cluster changes, i.e., the spin-flip takes place. In this time, the magnetic fluctuation of the cluster becomes large and the magnetic excitation energies, except for that of one excitation mode, overlap with the excitation spectrum of the spin wave. We also show that, by the overlap, sharp peaks and dips occur in the excitation spectrum of the spin wave.     

Enzymatic synthesis of (-)- and (+)-acetoxyhexamides and (-)- and (+)-hydroxyhexamides.

The enantioselective hydrolysis of (+/-)-4-(1-acetoxyethyl)-N-(cyclohexylcarbamoyl)-benzenesulfona mides 3 with lipase Amano P from Pseudomonas sp. in a water-saturated solvent gave (R)-4-(1-hydroxyethyl)-N-(cyclohexylcarbamoyl)benzenesulfonamide 2 (39%, > 99% ee) and unchanged (S)-3 (50%, 62% ee). On the other hand, enantioselective esterification of (+/-)-2 with lipase Amano P in the presence of vinyl acetate provided (R)-3 (41%, > 99% ee) and unchanged (S)-2 (46%, 78% ee).     

Conversion of Molecular Oxygen into a Hydroperoxo Species by Ring-Opening Protonation of a Cyclic η2-Peroxo Intermediate: Characterization of the η2-Peroxo and Hydroperoxo Complexes

A transition metal–hydroperoxo species is formed by the oxygenation of a low-valent rhodium precursor followed by a protonation of the resulting η²-O₂ ligand; the latter process is assisted by an intramolecular hydrogen-bonding interaction (see scheme). This process is the first structural evidence for an effective method for the activation of molecular oxygen as postulated for the cytochrome P-450 system.     

Studies on molecular composite. III. Nano composites consisting of poly(p‐phenylene benzobisthiazole) and thermoplastic polyamide

A bulk sample of a nano composite consisting of poly(p‐phenylene benzobisthiazole) (PBZT) and a thermoplastic matrix polymer was obtained by polymer blending of a matrix polymer of thermoplastic aromatic polyamide and a reinforcing polymer of a copolymer consisting of a precursor of PBZT and a fragment in common with the matrix polymer, using organic solvent, followed by molding. The phase structure of obtained specimens was varied by controlling the molding process conditions. In particular, the mechanical properties, heat resistance, and chemical resistance of the matrix polymer of a bulk specimen which has a three‐dimensional network structure of PBZT were improved drastically, even when only a small amount of the reinforcing material was added. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 209–218, 1999     

Combining Photoredox‐Catalyzed Trifluoromethylation and Oxidation with DMSO: Facile Synthesis of α‐Trifluoromethylated Ketones from Aromatic Alkenes

Trifluoromethylated ketones are useful building blocks for organic compounds with a trifluoromethyl group. A new and facile synthesis of ketones with a trifluoromethyl substituent in the α‐position proceeds through a one‐pot photoredox‐catalyzed trifluoromethylation–oxidation sequence of aromatic alkenes. Dimethyl sulfoxide (DMSO) serves as a key and mild oxidant under these photocatalytic conditions. Furthermore, an iridium photocatalyst, fac[Ir(ppy)₃] (ppy=2‐phenylpyridine), turned out to be crucial for the present photoredox process.