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91.
Zaitsu K Katagi M Kamata H Kamata T Shima N Miki A Iwamura T Tsuchihashi H 《Journal of mass spectrometry : JMS》2008,43(4):528-534
A reliable and accurate GC-MS method was developed that allows both mass spectrometric and chromatographic discrimination of the six aromatic positional isomers of trimethoxyamphetamine (TMA). Regardless of the trifluoroacetyl (TFA) derivatization, chromatographic separation of all the investigated isomers was achieved by using DB-5 ms capillary columns (30 m x 0.32 mm i.d.), with run times less than 15 min. However, the mass spectra of the nonderivatized TMAs, except 2,4,6-trimethoxyamphetmine (TMA-6), showed insufficient difference for unambiguous discrimination. On the other hand, the mass spectra of the TFA derivatives of the six isomers exhibited fragments with significant intensity differences, which allowed the unequivocal identification of all the aromatic positional isomers investigated in the present study. This GC-MS technique in combination with TFA derivatization, therefore, is a powerful method to discriminate these isomers, especially useful to distinguish the currently controlled 3,4,5-trimethoxyamphetmine (TMA-1) and 2,4,5-trimethoxyamphetmine (TMA-2) from other uncontrolled TMAs. 相似文献
92.
In copper(I) complex [Cu(dmphen)(2)]+ (dmphen = 2,9-dimethyl-1,10-phenanthroline), a "flattening" structural change is induced with 1MLCT excitation, which is a prototype of the structural change accompanied with Cu(I)/Cu(II) conversion in copper complexes. Femtosecond and picosecond emission dynamics of this complex were investigated in solution at room temperature with optically allowed S(2) <-- S(0) photoexcitation. Time-resolved emission was measured in the whole visible region, and the lifetimes, intrinsic emission spectra, and radiative lifetimes of the transients were obtained by quantitative analysis. It was concluded that the initially populated S(2) state is relaxed with a time constant of 45 fs to generate the S1 state retaining the perpendicular structure, and the D(2d) --> D(2) structural change (the change of the dihedral angle between the two ligand planes) occurs in the S(1) state with a time constant of 660 fs. The intersystem crossing from the S(1) state to the T(1) state takes place after this structural distortion with a time constant of 7.4 ps. Importantly, the temporal spectral evolution relevant to the structural change clearly exhibited an isoemissive point around 675 nm. This manifests that there exists a shallow potential minimum at the perpendicular geometry on the S1 surface, and the S1 state stays undistorted for a finite period as long as 660 fs before the structural distortion. This situation is not expected for the structural change induced by the ordinary (pseudo-)Jahn-Teller effect, because the distortion should be induced by the spontaneous structural instability at the perpendicular structure. This result sheds new light on the present understanding on the structural change occurring in the metal complexes. 相似文献
93.
Duan WL Iwamura H Shintani R Hayashi T 《Journal of the American Chemical Society》2007,129(7):2130-2138
A full overview on the use of chiral phosphine-olefin ligands 1 in the rhodium-catalyzed asymmetric 1,4-addition of arylboronic acids to alpha,beta-unsaturated carbonyl compounds is described. Effective chiral environment of a Rh/1 complex was shown to resemble that of a Rh/(R,R)-Ph-bod* complex by comparing the experimental results as well as the X-ray crystal structures. High catalytic activity of a Rh/1 complex was disclosed and the catalytic cycle involving a trimer-monomer equilibrium was established through mechanistic studies using a reaction calorimeter and (31)P NMR spectroscopy. A negative nonlinear effect derived from an inactive trimer-active monomer equilibrium of the catalyst was also successfully observed. 相似文献
94.
Jun Kawakami Junko Nakamura Michiko Iwamura 《Journal of photochemistry and photobiology. A, Chemistry》2001,140(3):199-206
The effects of solvent polarity on the fluorescence spectra and fluorescence decays of β-(1-pyrenyl)ethyl p-cyanobenzoate (P2CN) were investigated in detail using binary solvents consisting of various mixing ratios of isooctane-ethyl acetate or ethyl acetate-acetonitrile (dielectric constants ()=1.94–36.2). Whereas both the intensity and wavelength maxima of an intramolecular exciplex emission (EX) are dependent on the solvent polarity, only the intensity of an emission from the locally excited pyrene (LE) is dependent on the solvents used. When monitored at 377 nm, the picosecond SPC (single photon counting) measurements reveal a slow decay (>150 ns) in addition to a fast decay (<1 ns) of the locally excited P2CN. There are also two decays for the EX which vary the intensity ratios by the monitored wavelength. The decay rate constants, kEX1 and kEX2, have a good linear correlation with the dielectric constants of the solvents, indicating that there exist two kinds of exciplexes. It is suggested that the decays of the locally excited-state of P2CN are so fast due to result of the efficient electron transfer that the two kinds of intramolecular exciplexes are formed from the two discrete conformers in the ground state. 相似文献
95.
96.
97.
Takeru Iwamura Ikuyoshi Tomita Masato Suzuki Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2000,38(18):3440-3449
The chemical modification of polymers having amide moieties was carried out with p‐toluenesulfonyl isocyanate. The resulting polymers revealed high hydrolytic character. For example, poly(acrylamide) was refluxed with an excess amount of p‐toluenesulfonyl isocyanate in THF for 50 h to obtain a structurally modified polymer in 76% yield, whose sulfonylurea functionality was 100%. The resulting polymer was subjected to hydrolysis in a 1 M NaOH solution at 50 °C to convert 90% of the sulfonylurea in the side chain to the carboxylic acid moieties. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3440–3449, 2000 相似文献
98.
Megumi Tanaka Kenji Matsuda Tetsuji Itoh Hiizu Iwamura 《Angewandte Chemie (International ed. in English)》1998,37(6):810-812
Despite antiferromagnetic coupling between any two neighboring spins, parallel alignment of the 3d spins of the MnII ions and the 2p spins of the organic ligand is observed for the (degenerate) ground state of [{Mn(hfac)2}2(bnn)] (shown on the right). The “butterfly”-shaped arrangement of the spins contributes to this noteworthy spin configuration. hfac=hexafluoroacetylacetonate, bnn=2,2′-bis(1-oxyl-3-oxide-4,4,5,5-tetramethylimidazolinyl). 相似文献
99.
Stabilization of p-Phenylenebis(N-tert-butylaminoxyl) Relative to p-Benzoquinonediimine N,N′-Dioxide
Shuichi Nakazono Satoru Karasawa Noboru Koga Hiizu Iwamura 《Angewandte Chemie (International ed. in English)》1998,37(11):1550-1552
Steric interactions between methoxy and tert -butyl groups are the reason that 2 only exists as p-phenylenebis(N-tert-butylaminoxyl) B . The p-phenylenebis(N-tert-butylaminoxyl) 1 has the p-quinonediimine N,N′-dioxide structure Q in solution as well as in the crystalline state. 相似文献
100.
Takeru Iwamura Kazufumi Ashizawa Kaoru Adachi Masato Takasaki 《Journal of polymer science. Part A, Polymer chemistry》2019,57(24):2415-2419
Anionic hydrogen‐transfer homopolymerization of N‐isopropylacrylamide (NIPAAm) was carried out using t‐BuOK as an initiator in DMF under microwave irradiation. After 100 W of microwave was irradiated to the reaction mixture at 140°C for 6 h in the temperature control mode, corresponding polymer was obtained in 10% yield. In the case of conventional oil bath heating, by contrast, corresponding polymer was not obtained in similar anionic polymerization conditions. With 100 W and 2.45 GHz of microwave irradiation, formation of the polymer was obtained. Microwave‐assisted anionic hydrogen‐transfer copolymerization of NIPPAm and acrylamide (AAm) led to the formation of thermo‐sensitive copolymers whose thermo‐sensitivity was controlled by the NIPAAm/AAm unit ratio. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2415–2419 相似文献