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421.
Qiu H Mallik AK Takafuji M Ihara H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(26):7288-7297
A new ionic-liquid monomer, 1-vinyl-3-octadecylimidazolium bromide ([C(18)VIm]Br), was prepared and polymerized on porous silica particles by means of a surface-initiated radical chain-transfer reaction. Further modification for functionalization was performed through the exchange of counteranions from bromide to methyl orange (MO). Two new silica-poly(octadecylimidazolium) (Sil-PImC(18)) hybrid materials (Sil-PImC(18)-Br and Sil-PImC(18)-MO) were synthesized and characterized by elemental analysis, thermogravimetric analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), and solid-state (13)C CP/MAS NMR spectroscopy. Sil-PImC(18)-MO presented ultra-high shape selectivity for constrained isomers of polycyclic aromatic hydrocarbons (PAHs) both in reversed- and normal-phase HPLC when used as the stationary phase. Fundamental aspects of the molecular shape selectivity were evaluated by using Standard Reference Material (SRM) 869b; the column selectivity test mixture for liquid chromatography. The impact of this phase was also demonstrated by the separation of SRM 1647e (16 priority pollutant PAHs) and several steroid isomers. Enhanced selectivity could be explained by the highly oriented arrangement between the octadecylimidazolium chain and a rigid segment of MO. These findings may open a new window of research for the design of materials used in chromatographic supports, solid extraction, catalysis, and electrolytes by simple modifications of the counterions in the poly(ionic liquid) analogous phase. 相似文献
422.
423.
Aimé C Manet S Satoh T Ihara H Park KY Godde F Oda R 《Langmuir : the ACS journal of surfaces and colloids》2007,23(26):12875-12885
A new family of self-assembling systems based on nucleoamphiphiles is described. Nano to micrometric left-handed helix formation in aqueous solution was induced simply by complexing a GMP or an AMP with a nonchiral monocationic amphiphile. The assembling behavior such as micellar formation, monolayer at air-water interface, as well as the aggregates in solution of these nucleoamphiphiles are strongly influenced by the presence of nucleosides in solution. The observed effects depend on the properties of complexed nucleotides and nucleosides with a complex mixture of pi stacking, hydrophobicity of the bases, and hydrogen bonding. 相似文献
424.
Suzuki AZ Watanabe T Kawamoto M Nishiyama K Yamashita H Ishii M Iwamura M Furuta T 《Organic letters》2003,5(25):4867-4870
Caged compounds can be used to regulate the spatial and temporal dynamics of signaling molecules in live cells. Photochemical properties of coumarin-4-ylmethoxy carbonates (1a-d) are investigated to construct caged compounds of hydroxy-containing molecules. All the compounds possess desired properties as phototriggers for alcohols and phenols. The 6-bromo-7-hydroxycoumarin-4-ylmethoxycarbonyl (Bhcmoc) group has the highest photochemical efficiency and is applied to make caged compounds of 1,2-dioctanoylglycerol (diC(8)), Tyr-OMe, and adenosine. [reaction: see text] 相似文献
425.
Rhile IJ Markle TF Nagao H DiPasquale AG Lam OP Lockwood MA Rotter K Mayer JM 《Journal of the American Chemical Society》2006,128(18):6075-6088
Three phenols with pendant, hydrogen-bonded bases (HOAr-B) have been oxidized in MeCN with various one-electron oxidants. The bases are a primary amine (-CPh(2)NH(2)), an imidazole, and a pyridine. The product of chemical and quasi-reversible electrochemical oxidations in each case is the phenoxyl radical in which the phenolic proton has transferred to the base, (*)OAr-BH(+), a proton-coupled electron transfer (PCET) process. The redox potentials for these oxidations are lower than for other phenols, predominately from the driving force for proton movement. One-electron oxidation of the phenols occurs by a concerted proton-electron transfer (CPET) mechanism, based on thermochemical arguments, isotope effects, and DeltaDeltaG(++)/DeltaDeltaG degrees . The data rule out stepwise paths involving initial electron transfer to form the phenol radical cations [(*)(+)HOAr-B] or initial proton transfer to give the zwitterions [(-)OAr-BH(+)]. The rate constant for heterogeneous electron transfer from HOAr-NH(2) to a platinum electrode has been derived from electrochemical measurements. For oxidations of HOAr-NH(2), the dependence of the solution rate constants on driving force, on temperature, and on the nature of the oxidant, and the correspondence between the homogeneous and heterogeneous rate constants, are all consistent with the application of adiabatic Marcus theory. The CPET reorganization energies, lambda = 23-56 kcal mol(-)(1), are large in comparison with those for electron transfer reactions of aromatic compounds. The reactions are not highly non-adiabatic, based on minimum values of H(rp) derived from the temperature dependence of the rate constants. These are among the first detailed analyses of CPET reactions where the proton and electron move to different sites. 相似文献
426.
We construct an ab initio generic structure for a predimension function with a positive rational coefficient less than or equal to 1 which is unsaturated and has a superstable non-ω-stable theory. 相似文献
427.
Miyajima K Himeno H Yamada A Yamamoto H Mafuné F 《The journal of physical chemistry. A》2011,115(9):1516-1520
Trimetallic cluster ions containing Ta and other metal elements were prepared in the gas phase by a triple laser-ablation technique in a controlled manner. We have measured the abundances and their thermal stabilities, using time-of-flight mass spectrometry. Taking advantage of specific abundance distribution of the trimetallic cluster ions (magic stoichiometry), relative to the distinguished stabilities, the coalescence or the segregation of Ta and the other elements in the subnanometer sized clusters was discussed. We found that Nb, W, and Mo, which are categorized as elements with a high heat of vaporization, readily coalesce with Ta, while V, Al, Co, and Pt, which are categorized as elements with a low heat of vaporization, tend to be segregated from Ta. Our experiments, along with the calculation by another research group, suggest that the binding energies of atoms are related to the coalescence or segregation of clusters in the gas phase. 相似文献
428.
J.H. Ha J.C. Kim C.S. Lee J.Y. Huh C.-B. Moon Y. Gono S. Mitarai T. Morikawa M. Shibata H. Watanabe M. Miyake E. Komatsu A. Odahara E. Ideguchi X.H. Zhou 《The European Physical Journal A - Hadrons and Nuclei》1998,1(3):247-248
High-spin states of odd-odd 168Lu were observed up to 18ħ for the first time using the 159Tb(13C, 4nγ)168Lu reaction at E
13C= 58.5 MeV. γ-γ coincidence, E
γ singles, excitation function, and the DCO ratios were measured. Two rotational bands with signature splitting were populated,
among which the lower-energy band is identified as π 7/2+[404] ⊗ν 5/2+[642] in view of alignment and energy systematics.
Received: 27 October 1997 相似文献
429.
430.
Prof. Ming-Shui Yao Prof. Ken-ichi Otake Jiajia Zheng Masahiko Tsujimoto Dr. Yi-Fan Gu Lu Zheng Dr. Ping Wang Dr. Shivanna Mohana Dr. Mickaele Bonneau Tomoyuki Koganezawa Tetsuo Honma Hirotaka Ashitani Shogo Kawaguchi Prof. Yoshiki Kubota Prof. Susumu Kitagawa 《Angewandte Chemie (International ed. in English)》2023,62(35):e202308990
A one-stone, two-bird method to integrate the soft porosity and electrical properties of distinct metal–organic frameworks (MOFs) into a single material involves the design of conductive-on-insulating MOF (cMOF-on-iMOF) heterostructures that allow for direct electrical control. Herein, we report the synthesis of cMOF-on-iMOF heterostructures using a seeded layer-by-layer method, in which the sorptive iMOF core is combined with chemiresistive cMOF shells. The resulting cMOF-on-iMOF heterostructures exhibit enhanced selective sorption of CO2 compared to the pristine iMOF (298 K, 1 bar, S from 15.4 of ZIF-7 to 43.2–152.8). This enhancement is attributed to the porous interface formed by the hybridization of both frameworks at the molecular level. Furthermore, owing to the flexible structure of the iMOF core, the cMOF-on-iMOF heterostructures with semiconductive soft porous interfaces demonstrated high flexibility in sensing and electrical “shape memory” toward acetone and CO2. This behavior was observed through the guest-induced structural changes of the iMOF core, as revealed by the operando synchrotron grazing incidence wide-angle X-ray scattering measurements. 相似文献