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Reaction of L- and DL-N-acetylmethionine (Hacmet) and Ag(2)O in water at ambient temperature afforded the remarkably light-stable silver complexes {[Ag(L-acmet)]}(n) (1) and {[Ag(2)(D-acmet)(L-acmet)]}(n) (2), respectively. The color of the solids and aqueous solutions of 1 and 2 did not change for more than 1 month under air without any shields. The light stability of these two silver(I) complexes is much higher than that of silver(I) methioninate {[Ag(2)(D-met)(L-met)]}(n) (3) (Hmet = methionine), silver(I) S-methyl-L-cysteinate {[Ag(L-mecys)]}(n) (4), and silver(I) L-cysteinate {[Ag(L-Hcys)]}(n) (5). X-ray crystallography of 1 obtained by vapor diffusion revealed that ladder-like coordination polymers with two O- and two S-donor atoms were formed. The acetyl group of acmet(-) prevents chelate formation of the ligand to the metal center, which is frequently observed in amino acid metal complexes, but allows for formation of hydrogen bonds between the ligands in the crystals of 1. These two silver(I) N-acetylmethioninates showed a wide spectrum of effective antimicrobial activities against gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and yeasts (Candida albicans and Saccharomyces cerevisiae), the effectiveness of which was comparable to that of water-soluble Ag-O bonding complexes. 相似文献
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Miura T Kasuga H Imai K Ina M Tada N Imai N Itoh A 《Organic & biomolecular chemistry》2012,10(11):2209-2213
A fluorous organocatalyst promotes direct asymmetric aldol reactions of aromatic aldehydes with ketones in brine to afford the corresponding anti-aldol products in high yield with up to 96% ee. Fluorous organocatalyst can be readily recovered by solid phase extraction using fluorous silica gel and reused without purification. 相似文献
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Masayuki Nogami Yusuke Daiko Yoichi Goto Yoshitaka Usui Toshihiro Kasuga 《Journal of Sol-Gel Science and Technology》2003,26(1-3):1041-1044
We have investigated the proton conductivities of the sol-gel-derived P2O5-SiO2 glass at –50 to 120°C. The obtained glass is porous, where the surface area, pore volume and pore diameter are 740 m2/g, 0.5 cm3/g and <5 nm, respectively. The freezing temperature of water molecules adsorbed in the pores was –20°C, which is much lower than that of free liquid water due to the quantum size effect of the water confined in the pores. The electrical conductivities followed the Arrhenius equation in the temperatures between –20 and 120°C. Below –20°C, the adsorbed-water molecules were frozen, resulting in a rapid decrease of the proton conductivity. Considering the high conductivity, chemical and thermal stability, this oxide glass membranes have potential for the fuel cell membrane. 相似文献
35.
Katsuhiko Iwase Shinnosuke Kasuga Takahiro Kawai Yuta Matsushima 《Journal of Sol-Gel Science and Technology》2012,64(1):170-177
A new water-soluble precursor of BaTiO3 was prepared from citratoperoxotitanate and barium citrate as the Ti and Ba sources, respectively. The water-soluble precursor was easily solved in water to form a stable solution, which produced BaTiO3 by heat-treatment at 500 °C and above. A water-based dip-coating technique demonstrated a potential application as the coating solution of BaTiO3. Transparent BaTiO3 films were formed on the quartz-glass substrates with an increment of typically 9 nm per coating with 0.05 mol dm?3 solution. The transmittance of the 180 nm-thick film attained almost 90 % at the maximum and the overall transmittance was above 60 % over the visible region. The polycrystalline film was composed of BaTiO3 grains smaller than 200 nm. Although the film was an insulator, it was not suited for the dielectric application because of the structural problems due to the relatively low density and the thinness of the BaTiO3 layer. The BaTiO3 pellet obtained from the water soluble precursor by condensation, pyrolysis and sintering showed the good dielectric properties with εr = 3,500 and tan δ = 0.027 with a sintering temperature of 1,375 °C. 相似文献
36.
Moriyuki Sato Yuji Tada Shinji Nakashima Ken‐ichi Ishikura Makoto Handa Kuninobu Kasuga 《Journal of polymer science. Part A, Polymer chemistry》2005,43(7):1511-1525
Novel thermotropic liquid‐crystalline (LC) copolyesters were prepared with three disubstituted (4,4′‐, 3,4′‐, and 3,3′‐) dioxydiundecanol derivatives of terphenyl analogues of 1,3,4‐thiadiazole [2,5‐diphenyl‐1,3,4‐thiadiazole (DPTD)], and their optical and electrochemical properties were examined. Their structures were characterized with Fourier transform infrared, 1H NMR spectroscopy, and elemental analyses. The thermal and mesomorphic properties of the copolyesters were investigated with differential scanning calorimetry measurements, polarized microscopy observations, and X‐ray analyses; the data suggested that these copolymers formed LC smectic or nematic phases. The mesomorphic tendency decreased in the following order: 4,4′‐DPTD and 3,4′‐DPTD copolyesters > 4,4′‐DPTD and 3,3′‐DPTD copolyesters > 3,4′‐DPTD and 3,3′‐DPTD copolyesters. Solution and solid‐state ultraviolet–visible (UV–vis) and photoluminescence spectra indicated that the copolyesters displayed maximum absorbances and blue emissions according to the DPTD unit; the peak maxima of absorption and emission spectra of the copolyesters shifted to lower wavelengths in the aforementioned order for the LC properties. Cyclic voltammetry measurements indicated that the electrochemical band gaps of the polyesters estimated from the onset of reduction and oxidation processes were almost the same as the optical band gaps determined from the solid‐state UV–vis spectral data. The DPTD unit enhanced the hole‐injection barrier and improved the charge‐injection balance in these polyesters. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1511–1525, 2005 相似文献
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Tsuyoshi Miura Kie ImaiHikaru Kasuga Mariko InaNorihiro Tada Nobuyuki ImaiAkichika Itoh 《Tetrahedron》2011,67(34):6340-6346
Fluorous organocatalyst 3 promotes direct asymmetric aldol reactions of ketones with aldehydes in brine, leading to the synthesis of the corresponding anti-aldol products in high yields with up to 96% ee. Fluorous organocatalyst 3 is easily recovered by solid-phase extraction using fluorous silica gel and can be reused up to five times without purification. 相似文献