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981.
New dinuclear copper(I) complexes [Cu2(micro-X)2(micro-1,8-naphthyridine)(PPh3)2] (X=I, Br) having the butterfly-shaped {Cu2(micro-X)2} unit show red phosphorescence at room temperature in the solid state. Molecular orbital calculations show that the emissions of the new complexes are not directly related to their short Cu...Cu separations [2.6123(5) and 2.6271(4) A] and are assignable to the triplet charge-transfer excited states from the {Cu2(micro-X)2} core to 1,8-naphthyridine. 相似文献
982.
Ju MJ Yang DH Takahara N Hayashi K Toko K Lee SW Kunitake T 《Chemical communications (Cambridge, England)》2007,(25):2630-2632
Highly sensitive and selective detection of 2,4-DNT, a representative explosive, was achieved by the synergic effect of molecular imprinting and host (cyclodextrin)-guest interaction in ultrathin layers of TiO(2) and SiO(2) gel; the detection limit using cSPI measurements reached nM concentration. 相似文献
983.
Bisindolylmaleimides with large Stokes shift and long-lasting chemiluminescence properties 总被引:1,自引:0,他引:1
Various bisindolylmaleimides have fluorescence emission maxima wavelengths longer than 500 nm, large Stokes shifts longer than 200 nm, different fluorescence emission wavelengths at an excitation wavelength of 365 nm, and a long-lasting chemiluminescence. The expansion of the pi-conjugation, the pi-bond electronic structure, and oxidation of the C=C bond at the 2,3-position of the maleimide moiety are crucial for producing these fluorescence and chemiluminescence properties. 相似文献
984.
The flavoprotein D-amino acid oxidase (DAO) degrades the gliotransmitter D-Ser, a potent activator of N-methyl-D-aspartate-type glutamate receptors. A body of evidence suggests that DAO, together with its activator, G72 protein, may play a key role in the pathophysiology of schizophrenia. It has also been suggested that 3,4-dihydroxy-D-phenylalanine (D-DOPA), the stereoisomer of 3,4-dihydroxy-L-phenylalanine (L-DOPA), is oxidized by DAO and converted to dopamine via an alternative biosynthetic pathway. We determined the crystal structures of human DAO in complex with the reaction products of two clinically important substrates, D-Ser and D-DOPA. Kinetic data show that the maximum velocity is much greater for D-DOPA than that for D-Ser, which strongly supports the proposed alternative pathway for dopamine biosynthesis in the treatment of Parkinson's disease. In addition, biochemical characterization of human DAO indicates that it binds FAD more weakly than does porcine D-amino acid oxidase (pDAO) and exists as a stable homodimer, even in the apoprotein form. Determination of the structures of human DAO in various states reveals that, in contrast to pDAO, the hydrophobic-Val-Ala-Ala-Gly-Leu (VAAGL) stretch (residues 47-51, structurally ambivalent peptide) located at the si-face of the flavin ring assumes a uniquely stable conformation, which provides a structural basis for the unique kinetic features of human DAO. 相似文献
985.
Sugimori K Ito T Takata Y Ichitani K Nagao H Nishikawa K 《The journal of physical chemistry. A》2007,111(38):9417-9423
The above-threshold dissociation of the ground state of a OH molecule under intense nonresonant laser pulses has been studied using the time-dependent Schr?dinger equation with discrete variable representation. The applied field is assumed as a two-color mixed nonresonant laser pulses which has the nonresonant frequency omega and the overtone 2omega. After modulating the relative phase factor between the omega and 2omega pulse, we extracted a three-photon absorption peak or a five-photon absorption peak in the ATD spectrum. 相似文献
986.
Than S Maeda H Irie M Itoh S Kikukawa K Mishima M 《The journal of physical chemistry. A》2007,111(27):5988-5994
Free energy changes (DeltaG degrees , copper cation basicity) for the reaction L(2)Cu(+) = Cu(+) + 2L were obtained in the gas phase for substituted pyridines based on the measurement of ligand-exchange equilibria in a Fourier transform ion cyclotron resonance (FT-ICR) spectrometer. For 3- and 4-substituted pyridines, the relative copper cation basicities (DeltaCCB[L(2)Cu(+)]) were linearly correlated with the corresponding gas-phase proton basicities (DeltaGB) with a slope of 1.01. On the basis of a linear relationship between the calculated copper cation basicities of dimeric and monomeric complexes at MP2/6-311+G(2p,2d)//B3LYP/6-311G*, DeltaCCB[L(2)Cu(+)](calcd) = 1.54DeltaCCB[LCu(+)](calcd), the substituent effect on the DeltaCCB for the first ligand was estimated to be 0.66 times smaller than the corresponding DeltaGB. A comparison with the corresponding results for other Lewis cation basicity of the pyridine system showed that the magnitude of the substituent effect decreases in the order H(+) (1.00) > Me(3)Si(+) (0.95) > Cl(+) (0.83) > Cu(+) (0.66) > Li(+) (0.47). This change was associated with the natural charges at the Lewis cation moiety and the natural atomic orbital (NAO) bond order of the M+-N bond of the complex ion, indicating the decrease in covalent character of the M(+)-N bond in this order. Furthermore, when a variety of neutral bases such as amines, carbonyl compounds, and ethers were included in a comparison between CCB[L(2)Cu(+)] and GB, it was found that there is a good linear relationship with significant deviations of small molecules and bulky tributylamine, which is attributed to their different steric environment at the binding sites from others, while there is no simple linear relationship with the lithium cation basicities (LCB). The similarity of the substituent effect between CCB[L(2)Cu(+)] and GB reflects the covalent character in the Cu(+) interaction. In conclusion, although the ionic (ion-dipole interaction) nature of the Cu(+) interaction results in a smaller substituent effect than that for the protonation, the covalent nature also plays an important role in the Cu(+) interaction with neutral molecules. 相似文献
987.
Kiyoshi Endo Tomotsugu Shiroi Kiyoshi Murata 《Journal of polymer science. Part A, Polymer chemistry》2001,39(1):145-151
The thermal polymerization of styrene (St) in the presence of cyclic 1,2‐disulfides at 120 °C was investigated. In the polymerization of St in the presence of 1,2‐dithiane (DT), that is, six‐member cyclic 1,2‐disulfide, the polymer yields and molecular weights increased with the reaction time. The linear relation between the polymer yields and molecular weights was observed, and the line passed through an original point. The molecular weight distributions of the polymers remained almost constant but were not narrow. For this polymerization with a living nature, we proposed the following mechanism: the propagating St radical reacted with thiyl radicals derived from DT, leading to the formation of dormant species, and the formed C S bond of the dormant was dissociated again to give the propagating polystyryl radical and thiyl radical. Similar results were obtained in the thermal polymerization of St at 120 °C in the presence of 1,2‐dithiacycloheptane, that is, seven‐member cyclic 1,2‐disulfide. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 145–151, 2001 相似文献
988.
Fukuji Higashi Kiyoshi Mitani 《Journal of polymer science. Part A, Polymer chemistry》1999,37(19):3710-3714
When mixtures of terephthalic acid (TPA) and 1,6-naphthalenedicarboxylic acid (NDC) or 4,4′-dicarboxydiphenylether (DCDPE), TPA, and isophthalic acid (IPA) were reacted in pyridine (Py) with Tosyl chloride (TsCl)/DMF/Py to activate the diacids, the reaction mixture was soluble in Py, despite each of the separately activated diacids being insoluble. The solubility of the activated diacids was examined at a variety of acid compositions and temperatures. It was expected that a competitive reaction among the diacids with an aromatic diol in solution might be different from those in the melt, resulting in a different distribution of the acids in the copolymers. The TPA/NDC-phenylhydroquinone and DCDPE/TPA/IPA-chlorohydroquinone copolymers were prepared in solution using TsCl/DMF/Py as the condensing agent and the transition temperatures of these liquid crystalline copolyesters were compared to those obtained by melt copolycondensation. A practical depression of the transition temperature by the solution polycondensation was observed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3710–3714, 1999 相似文献
989.
Kiyoshi Endo Yuichi Matsuda 《Journal of polymer science. Part A, Polymer chemistry》1999,37(20):3838-3844
Copolymerization of styrene (St) and butadiene (Bd) with nickel(II) acetylacetonate [Ni(acac)2]-methylaluminoxane (MAO) catalyst was investigated. Among the metal acetylacetonates [Mt(acac)x] examined, Ni(acac)2 showed a high activity for the copolymerization of St and Bd giving copolymers having high cis-1,4-microstructure in Bd units in the copolymer. The effect of alkylaluminum as a cocatalyst on the copolymerization of St and Bd with the Ni(acac)2-MAO catalyst was observed, and MAO was found to be the most effective cocatalyst for the copolymerization. The monomer reactivity ratios for the copolymerization of St and Bd with the Ni(acac)2-MAO catalyst were determined to be rSt = 0.07 and rBd = 3.6. Based on the obtained results, it was presumed that the random copolymers with high cis-1,4-microstructure in Bd units could be synthesized with the Ni(acac)2-MAO catalyst without formation of each homopolymer. The polymerization mechanism with the Ni(acac)2-MAO catalyst was also discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3838–3844, 1999 相似文献
990.
R. C. Patil K. Kuratani M. Nakayama K. Ogura 《Journal of polymer science. Part A, Polymer chemistry》1999,37(14):2657-2665
Poly(o-toluidine) emeraldine base (EB) has been protonated with d,l -camphor sulfonic acid (HCSA). The CSA-doped poly(o-toluidine) (POT-CSA) is completely soluble in m-cresol, and the electrical conductivity is ∼ 28 S/cm. The incorporation of CSA has been proved by means of UV-Vis and IR spectroscopy. Thermogravimetric (TG)/mass (MS) analysis shows that POT-CSA is stable up to 180°C indicating the processability with other insulating polymers upto this temperature. TG curve of POT-CSA yields a four step decomposition pattern, and the degradation of the polymer backbone starts at 430°C. The thermal elimination of CSA occurs in the temperature range of 180 to 430°C. The viscometric and spectroscopic results suggest the change in molecular conformation from the compact coil to the expanded coil type which is enhanced by increasing the protonation level of EB by the addition of HCSA. The conductivity data were well equivalent to the viscometric data. Furthermore, POT-CSA-ABS (acrylonitrile/butadiene/styrene) blends were successfully fabricated with an extremely low percolation threshold of 2.66%. The scanning tunneling microscopic (STM) results reveal that the low percolation threshold reflects the formation of interconnecting path of conducting particles in ABS matrix. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2657–2665, 1999 相似文献