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931.
Yu Liu Shang Li Xiao-Peng Bai Takehiko Wada Yoshihisa Inoue 《Supramolecular chemistry》2013,25(4):529-537
Abstract Calorimetric titrations have been performed for the first time in anhydrous acetonitrile at 25°C to give the complex stability constant (K S) and thermodynamic quantities for the complexation of light lanthanoid(III) nitrates (La-Gd) with 5,11,17,23-tetra-tert-butyl-26,28-bis(cyanomethoxy)-25,27-dihydroxy-calix[4]arene (1) and 5,11,17,23-tetra-tert-butyl-26, 28-bis(2-aminoethoxy)-25,27-dihydroxycalix[4]arene (2). X-ray crystallographic structures of 1 and 2 were also determined and compared. Possessing the cyanomethoxy and aminoethyl substituents, 1 and 2 displayed strikingly different cation binding abilities and selectivity profiles with much higher K S values for La3+ and Ce3+, which may be related to the original structures in the solid state. Thus, the binding profile for 2 showed a rapid decrease in K S with decreasing ionic diameter from La3+ to Pr3+ and then became flat up to Gd3+, while 1 gave a very flat profile which is superimposable with that for 2 between Pr3+-Gd3+. Thermodynamically, the complexation is driven absolutely by enthalpy which compensates the entropic loss arising from the structural freezing of the calix[4]arene derivatives upon simultaneous binding of lanthanoid ion by the phenolic oxygen and acetonitrile molecule in the cavity. The general validity and the meaning of the compensative enthalpy-entropy relationship observed are discussed. 相似文献
932.
Lorena Machi Iliana C. Muñoz Refugio Pérez-González Mario Sánchez Motomichi Inoue 《Supramolecular chemistry》2013,25(8):665-673
Fluorescent response to pH has been studied on water-soluble pyrene-based bichromophores, (edtapy)H2 and (dtpapy)H3, in which two pyrenyl groups are linked by an ethylenediaminetetraacetate (EDTA) and a diethylenetriaminepentaacetate (DTPA) unit, respectively, through amide linkages. The excimer emission of the EDTA derivative is strengthened sharply with increasing pH at two steps; the first step is associated with the dissociation of acidic hydrogen from amino nitrogen in partially protonated species (edtapy)H? and the second step is attributable to the amide group. The excitation spectra have evidenced the formation of a static excimer in the ground state of completely deprotonated species (edtapy)2 ? . The close contact between pyrenyl groups in (edtapy)2 ? has been confirmed by density functional theory, which has also shown that the close contact is broken when amino nitrogen is protonated. The DTPA derivative exhibits a strong excimer emission, which shows an intensity–pH profile of an ‘off–on–off–on’ type. This rare pH response is ascribable to multiple protonation sites in the DTPA chain, as confirmed by 1H NMR. The novel pH-sensing capabilities in specific pH regions are due to the combination of the fluorescent group with the polyaminopolycarboxylate chains whose conformations are reversibly altered by protonation–deprotonation processes. 相似文献
933.
Yuji Tada Narimasa Moriya Takashi Inoue Atsuko Suzuki Shigeto Koyama 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):1555-1567
Abstract Novel cyclotriphosphazenes containing cyanato group (PZCN) derivatives were synthesized by a substitution reaction of 4-hydroxyphenoxycyclotriphosphazenes and cyanogen bromide (BrCN) in the presence of triethylamine (TEA). The PZCNs were characterized by FT-IR, liquid chromatography–mass spectrometry (LC-MS), 1H NMR, 13C NMR, and 31P NMR spectroscopy. Curing reactions of the PZCNs were evaluated by FT-IR spectroscopy, thermogravimetry/differential thermal analysis (TG/DTA), and differential scanning, calorimetry (DSC). The PZCNs exhibited an exothermic peak due to curing within the temperature range of 140–300°C by DSC. The PZCNs were completely cured at 220°C. The cured PZCNs exhibited high thermal stability up to 350°C, a high char-forming capability, and electrical properties, such as dielectric constants (Dks) between 2.68 and 2.87, and dissipation factors (Dfs) between 0.008 and 0.013 at 1 MHz. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. 相似文献
934.
α, β, γ δ-Tetraphenylporphinatoaluminum carboxylate (TPPA10COR) and phenoxide (TPPA10Ar) bring about the polymerization of β-lactone and epoxide to give polymers with controlled chain length having a carboxylic ester or phenoxy group at the end of each polymer molecule. Acrylate (TPPA10COCH=CH2) and p-vinylphenoxide (TPPA1-OC6H4,CH[dbnd]CH2 (p)) as initiator give polyester or polyether macromer with narrow molecular weight distribution. 相似文献
935.
Noboru Yoshida Kazuaki Harata Tetsuya Inoue Naohito Ito Kazuhiko Ichikawa 《Supramolecular chemistry》2013,25(2):63-67
Abstract The crystal structure and molecular recognition behaviour of a new chiral-amino cyclodextrin are reported; van der Waals interaction, hydrogen bond and the electrostatic interactions play an important role in the self-assembling process and chiral recognition for (R)-(-)-and (S)-(+)-mandelic acid. 相似文献
936.
Koichi Inoue Nuntawat Prayoonhan Haruhito Tsutsui Tasuku Sakamoto Maiko Nishimura Toshimasa Toyo'oka 《Journal of separation science》2013,36(8):1356-1361
Dichlorprop is available for agricultural use as a chiral pesticide. In this study, the stereoselective determination of dichlorprop enantiomers in tea samples such as green, black, jasmine, and oolong was developed by ultra performance LC with fluorescence spectrometry after covalent chiral derivatization. The separation was achieved on an Acquity BEH C18 column with the mobile phase consisting of 0.1% formic acid in acetonitrile/water at a flow rate of 0.4 mL/min. In the covalent chiral derivatization using (S)‐(+)‐4‐(N,N‐dimethylaminosulfonyl)‐7‐(3‐aminopyrrolidin‐1‐yl)‐2,1,3‐benzoxadiazole, the peak resolution between the S and R‐dichlorprop enantiomers was 2.6. LODs and LOQs values were 10 and 50 ng/mL standard solution. The linearity of the calibration curves yielded the coefficients (r2 > 0.99, ranging from 0.05 to 5 μg/mL) of determination of each of the dichlorprop enantiomers. SPE extraction was used for the sample preparation of dichlorprop in various tea samples. Recoveries were in the range of 82.4–97.6% with associated precision values (within‐day: 82.4–95.8%, n = 6, and between‐day: 83.7–97.6% for 3 days) for repeatability and reproducibility. Based on this result, our method has been proven to be highly efficient and suitable for the routine assay of dichlorprop enantiomers in various tea samples. We propose that the ultra performance LC assay after covalent chiral derivatization would be the renewed tools in the era of chiral stationary platform for chiral pesticide residues in foods. 相似文献
937.
938.
939.
Methodology and Computing in Applied Probability - In this article, we consider random occupancy models and the related problems based on the methods of generating functions. The waiting time... 相似文献
940.
Scattering and absorption in the tissues are major problems for in vivo imaging based on a fluorescence reflectance imaging
technique. We evaluated the quantitative relationship between body thickness and fluorescent signals from a deep abdominal
source in intact mice. Mice were injected with quantum dots (peak emission, 800 nm) into the right rear footpad, and fluorescent
signals from the iliac lymph node located deeply in the abdomen were assessed by fluorescence reflectance imaging. Stepwise
compression of the mouse abdomen to reduce the body thickness was attained using a homemade simple device. The iliac node
signals were weak and diffuse without compression but became stronger and more localized with decreasing body thickness. Using
excitation light of approximately 710 nm wavelength, the lymph node/background contrast increased about 16 times with a 4 mm
reduction in body thickness. Contrast enhancement was more evident using shorter wavelength excitation light. Overlying tissues
profoundly affect signals from a deep source in fluorescence reflectance imaging. Our simple compression method may contribute
to quantitatively assessing deep fluorescent sources. 相似文献