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121.
Hirotaka Furukawa Katsuhiro Ajito Machiko Takahashi Masatoki Ito 《Journal of Electroanalytical Chemistry》1990,280(2)
CO adsorbed on UPD and OPD (under- and overpotential deposited) Ag layers on a Pt electrode surface was studied by SERS and IRRAS in conjunction with cyclic voltammetry. Electrochemical activation of a uniform UPD Ag adlayer produced Ag clusters on the Pt electrode as well as bare Pt sites. The strong adsorption of CO on the UPD Ag/Pt electrode compared with a bulk Ag electrode is explained by the influence of the substrate Pt atoms. The degree of electron back-donation to CO increases the degree of lower frequency shifts of CO on the electrodes in the order Pt electrodes < monolayer Ag/Pt < multilayer Ag/Pt. 相似文献
122.
Minoru Yamaji Ai Suzuki Fuyuki Ito Shozo Tero-Kubota Seiji Tobita Bronislaw Marciniak 《Journal of photochemistry and photobiology. A, Chemistry》2005,170(3):253-259
Photodissociation of the carbon-X (X = Br and Cl) bonds in p-bromo- and p-chloromethylbenzophenone (BMBP and CMBP) in solution were investigated by time-resolved EPR and laser flash photolysis techniques. BMBP and CMBP were found to undergo ω-bond cleavage to yield the p-benzoylbenzyl radical (BBR) at 295 K, and the quantum yields (ΦBBR) were determined. The CIDEP signal originated from BBR formed upon decomposition of CMBP was obtained while that for BMBP was absent. By using triplet sensitization of acetone, the efficiencies (BBR) of the CX bond fission in the triplet states of BMBP and CMBP were determined. The agreement between the ΦBBR and BBR values for CMBP indicates that the CCl bond dissociation occurs only in the triplet state. In contrast to CMBP, the cleavage of the CBr bond in BMBP upon direct excitation was concluded to be the event only in the excited singlet state without triplet formation, whereas the triplet state was also reactive for ω-bond dissociation. The rate of CBr bond dissociation seemed to be greater than that of intersystem crossing from the S1 to the T1 state. Schematic energy diagrams of the excited states of BMBP and CMBP were shown, and the reaction profiles were discussed from the viewpoint of the CX bond enthalpies. 相似文献
123.
Yoshihiko Ito Yoshinori Inubushi Toru Sugaya Takeo Saegusa 《Journal of organometallic chemistry》1977,137(1):1-9
Reaction of carboxamides with Cu2O in the presence of t-butyl isocyanide gave new chelated copper(I) complexes, which probably are formed by the insertion of t-butyl isocyanide into the coppernitrogen bond of copper(I) amide isonitrile complexes, which were initially produced from the carboxamides and Cu2Ot-butyl isocyanide complex. The same chelated copper(I) complexes were prepared more readily by the reaction of the corresponding N-trimethylsilyl-carboxamides with Cu2Ot-butyl isocyanide complex. Reactions of the copper(I) complexes thus obtained with alkylating agents, such as alkyl halides, alkyl tosylates and triethyloxonium tetrafluoroborate, also were described. 相似文献
124.
Hideki Sugimoto 《Tetrahedron letters》2004,45(22):4213-4216
Enantioselective intramolecular radical cyclization of benzimidazolyl iodoalkenyl and iodoalkadienyl sulfones using chiral Lewis acids gave products with good enantioselectivity. Newly formed chiral centers could be induced effectively by enantioselective coordination to one of the sulfonyl oxygens. 相似文献
125.
Du Q Jerz G Ha Y Li L Xu Y Zhang Q Zheng Q Winterhalter P Ito Y 《Journal of chromatography. A》2005,1074(1-2):43-46
Salicin in the bark extract of Salix alba and amygdalin in the fruit extract of Semen armeniacae were each separated by slow rotary counter-current chromatography (SRCCC). The apparatus was equipped with a 40-L column made of 17 mm i.d. convoluted Teflon tubing. A 500g amount of crude extract containing salicin at 13.5% was separated yielding 63.5 g of salicin at 95.3% purity in 20h using methyl tert-butyl ether-l-butanol (1:3) saturated by methanol-water (1:5) as a stationary phase and methanol-water (1:5) saturated by methyl tert-butyl ether-1-butanol (1:3) as a mobile phase. A 400g amount of crude extract containing amygdalin at 55.3% was isolated to yield 221.2g of amygdalin at 94.1% purity in 19h using ethyl acetate-1-butanol (1:2) saturated by water as a stationary phase and water saturated by ethyl acetate-1-butanol (1:2) as a mobile phase. The flow rate of the mobile phase was 50 ml/min. The results show that industrial SRCCC separation of salicin and amygdalin is feasible using a larger column at a higher flow rate of the mobile phase. 相似文献
126.
Hiroshi Ito 《Tetrahedron letters》2005,46(50):8757-8760
Fourteen isomers of bis(formylmethano)C60 were isolated and characterized. A mixture of the bisadducts was obtained by the reaction of C60 with an α-formylsulfonium ylide, and then separated into 15 fractions by preparative HPLC, preparative TLC, and recycling preparative HPLC. Fourteen of the fifteen fractions were found to consist of a single isomer, respectively, which were assigned to the trans-2 (3 diastereo-isomers), trans-3 (3 diastereo-isomers), trans-4 (3 diastereo-isomers), equatorial (2 diastereo-isomers), and cis-2 (3 diastereo-isomers) bisadducts by the comparison of their UV/vis spectra with those of the bisadducts obtained by the Bingel-Hirsch reaction. The 1H and 13C NMR analysis, the transformation of the formyl groups, and the dipole moment calculation clarified the stereochemistry of the substituents on the two cyclopropane bridge-head carbons (in/in, in/out, and out/out). 相似文献
127.
The reaction of 2-functionalized 1-halo-2,n-enynes (n = 7 or 8) with a divalent titanium reagent, Ti(O-i-Pr)4/2i-PrMgCl, proceeded in a domino fashion to afford bicyclic compounds in good yields. 相似文献
128.
Tsuneyuki Sato Osamu Ito Shigeki Mori Takayuki Otsu 《Journal of polymer science. Part A, Polymer chemistry》1984,22(7):1661-1676
Poly(dimethylaminoethyl methacrylate N-oxide) (poly(DMAEMNO)) was prepared by oxidation of poly(dimethylaminoethyl methacrylate) with hydrogen peroxide in methanol. From thermogravimetric and IR spectroscopic investigations Cope elimination of amine oxide group in poly(DMAENO) was found to occur at 120–150°C. The postpolymerization of partially pyrolyzed polymer carrying vinyl ester group as pendant was performed with azobisisobutyronitrile at 60°C in methanol to give cross-linked polymer that was found to form hydrogel. Poly(DMAEMNO) gave metal–polymer complexes with CuCl2, ZnCl2, and CoCl2. Cobalt–polymer complex had a constitution of 1:2 of metal ion to amine oxide group, while copper– and zinc–polymer complexes seemed to have structures of 1:1 and 1:2 of metal ion to amine oxide group. Furthermore, polymer complexes of poly(DMAEMNO) with poly(methacrylic acid) and poly(acrylic acid) were found to be formed by mixing aqueous solutions of both polymers and also by radical polymerization of the acid monomers in the presence of poly(DMAEMNO). From elemental analysis, thermogravimetric investigation, and measurement of turbidity it was concluded that the resulting polymer–polymer complexes contained more than one acid monomer unit per one N-oxide unit. 相似文献
129.
Sakamoto S Ito A Kudo K Yoshikawa S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(15):3717-3726
The introduction of a flavin chromophore on the myoglobin (Mb) surface and an effective electron-transfer (ET) reaction through the flavin were successfully achieved by utilizing the self-assembly of heterostranded coiled-coil peptides. We have prepared a semiartificial Mb, named Mb-1alphaK, in which an amphiphilic and cationic alpha-helix peptide is conjugated at the heme propionate (Heme-1alphaK). Heme-1alphaK has a covalently bound iron-protoporphyrin IX (heme) at the N terminus of a 1alphaK peptide sequence. This sequence was designed to form a heterostranded coiled-coil in the presence of a counterpart amphiphilic and anionic 1alphaE peptide sequence in a parallel orientation. Two peptides, Fla(1)-1alphaE and Fla(31)-1alphaE, both incorporating a 10-methylisoalloxazine moiety as an artificial flavin molecule, were also prepared (Fla=2-[7-(10-methyl)isoalloxazinyl]-2-oxoethyl). Heme-1alphaK was successfully inserted into apomyoglobin to give Mb-1alphaK. Mb-1alphaK recognized the flavin-modified peptides and a two-alpha-helix structure was formed. In addition, an efficient ET from reduced nicotinamide adenine dinucleotide to the heme center through the flavin unit was observed. The ET rate was faster in the presence of Fla(1)-1alphaE than in the presence of Fla(31)-1alphaE or the equivalent molecule that has no peptide chain. These results demonstrate that the introduction of a functional chromophore on the Mb surface can be achieved by using specific peptide-peptide interactions. Moreover, the dependence of the ET rate on the position of the flavin indicated that the distance between the heme active site and the flavin chromophore was regulated by the three-dimensional structure of the designed polypeptide. 相似文献
130.
The electronic structure of the proflavine cation is studied by the SCF –ASMO –CI method using the Pariser–Parr–Pople approximations. It is shown that the band at 445 mμ may be assigned to the 1A1 → 1B1, transition polarized along the long axis of the molecule. The bands in the neighbourhood of 260 mμ, which are composed of three absorption bands, are tentatively assigned to the 1A1 → 1B1, 1A1 → 1B1, and 1A1 → 1A1 transitions, respectively, in order of decreasing wavelength. The spectrum of the acridine orange cation may be understood to have the same assignment as that of the proflavine cation. The acridine dye cations are well known for their dimerization with concentration. The intermolecular distances in these dimers are estimated from the band shifts due to the formation of dimers, using the exciton theory. The main contribution to the molecular interaction is shown to be the electrostatic dipole–dipole interaction. Since the first excitation band of the dye molecule which exhibits a remarkable change due to the formation of the DNA–acridine dye complex, is suggested to be polarized along the long axis, preference of the outside stacking or the intercalation model is qualitatively discussed from the spectral shift of the acridine dye bound to the DNA, assuming simple models. 相似文献