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992.
993.
The conformational and dynamic properties of 1-octanol in neat and in water-saturated states have been investigated by 1H NMR. It has been proved that neat 1-octanol is microheterogeneous in nature comprising regions enriched in either hydrocarbons or hydroxyl groups. A reversed micelle-like cluster model was proposed, where the octanol cluster has an inner polar core of hydrogen-bonded octanol hydroxyls and an outer shell of nonpolar alkyl chains radiating outside. It was also observed that the cluster structure of octanol experiences minor changes with the presence of water. In water-saturated octanol, water molecules associate via hydrogen bonding and reside in the innermost center of the polar region with restricted motion, whereas the octanol cluster structure is modified by loosening the compact structure. Moreover, the preferential solvations of both systems were tested and compared. It not only gives some clues about the microheterogeneity of the alcohol system and the structure of the cluster but also helps in advancing our understanding on the behavior and properties of the amphiphilic molecules system such as phospholipids. 相似文献
994.
Trans-3-(3-pyridyl) acrylic acid (PAA) was deposited on glassy carbon electrode (GCE) by electropolymerization in pH 7.0 phosphate buffer solution (PBS). The poly (3-(3-pyridyl) acrylic acid) (PPAA) film modified glassy carbon electrode shows an excellent electrochemical response for dopamine (DA), ascorbic acid (AA) and uric acid (UA). The cyclic voltammetry oxidation peaks for DA and AA, DA and UA, AA and UA are separated by 150 mV, 130 mV and 280 mV, respectively. This permits the simultaneous determination of AA, DA and UA. The interference of AA with the determination of DA could be eliminated because of the electrostatic interaction between DA cations and the negatively charged PPAA film at pH 7.0. The anodic peak currents of DA, AA and UA increase linearly with concentration in the range of 1-40 micromol L(-1), 10-400 micromol L(-1) and 1.6-80 micromol L(-1), respectively, with a correlation coefficient (r) always higher than 0.998. The detection limit is 0.06 micromol L(-1), 0.8 micromol L(-1) and 1.1 micromol L(-1) for DA, AA and UA, respectively. 相似文献
995.
A molecular basket with four cholate units assembled on a cone-shaped calix[4]arene assumed reversed micelle-like conformation in 5% methanol/carbon tetrachloride. The inwardly facing hydroxyl groups on the cholates concentrated the polar solvent from the mostly nonpolar mixture. Methanolysis of alkyl halides benefited from the concentrated pocket of methanol if the substrate was capable of entering the basket. Substrates that were too large or too hydrophobic to fit within the basket showed no rate acceleration. 相似文献
996.
Yan Z Xia S Gardlik M Seo W Maslak V Gallucci J Hadad CM Badjić JD 《Organic letters》2007,9(12):2301-2304
We have investigated Ag(I) mediated folding of a tridentate compound, containing three pyridine flaps tethered to a semirigid scaffold, into a molecular basket, using both experimental and theoretical methods. The basket formation has been shown to be highly favorable in organic media (Delta G degrees = -7.2 kcal/mol), with the assembly process allowing for another ligand to bind preferentially on the outer side. 相似文献
997.
To systematically explore the influence of the bulky aromatic ring skeleton with a large conjugated pi-system on the structures and properties of their complexes, six CuII, CoII, and NiII complexes with the anthracene-based carboxylic ligand anthracene-9-carboxylic acid (HL1), were synthesized and characterized, sometimes incorporating different auxiliary ligands: [Cu2(L1)4(CH3OH)2](CH3OH) (1), [Cu4(L1)6(L2)4](NO3)2(H2O)2 (2), {[Cu2(L1)4(L3)](CH3OH)0.25}infinity (3), [Co2(L1)4(L4)2(micro-H2O)](CH3OH) (4), {[Co(L1)2(L5)(CH3OH)2]}infinity (5), and {[Ni(L1)2(L5)(CH3OH)2]}infinity (6) (L2 = 2,2'-bipyridine, L3 = 1,4-diazabicyclo[2.2.2]octane, L4 = 1,10-phenanthroline, and L5 = 4,4'-bipyridine). 1 has a dinuclear structure that is further assembled to form a one-dimensional (1D) chain and then a two-dimensional (2D) network by the C-H...O H-bonding and pi...pi stacking interactions jointly. 2 takes a tetranuclear structure due to the existence of the chelating L2 ligand. 3 possesses a 1D chain structure by incorporating the related auxiliary ligand L3, which is further interlinked via interchain pi...pi stacking, resulting in a three-dimensional (3D) network. 4 also has a dinuclear structure and then forms a higher-dimensional supramolecular network through intermolecular pi...pi stacking and/or C-H...pi interactions. 5 and 6 are isostructural complexes, except they involve different metal ions, showing 1D chain structures, which are also assembled into 2D networks from the different crystallographic directions by interchain pi...pi stacking and C-H...pi interactions, respectively. The results reveal that the steric bulk of the anthracene ring in HL1 plays an important role in the formation of 1-6. The magnetic properties of the complexes were investigated, and the very long intermetallic distances result in weak magnetic coupling, with the exception of 1 and 3, which adopt the typical paddle-wheel structure of copper acetate and are thus strongly coupled. 相似文献
998.
999.
A simple and rapid bulk-modification method based on adding an amphiphilic copolymer during the fabrication process was employed to modify PDMS microchips. Poly(lactic acid)-poly(ethylene glycol) (PLA-PEG) was used as the additive substance. Compared to the native PDMS microchips, both the contact angle and the EOF of the bulk-modified PDMS microchips decreased. The effects of the additive loading and the pH on the EOF were investigated in detail. The bulk-modified PDMS microchips exhibited reproducible and stable EOF behavior. The application of the bulk-modified PDMS microchips was also studied and the results indicated that they could be successfully used to separate amino acids and to suppress protein adsorption. 相似文献
1000.
The novel amino-acid-containing polyoxometalate K6[Cu(Ala)2(H2O)2]2[Cu4(H2O)2\5(AsW9O34)2]*16H2O was synthesized from the rea ction of K10[Cu4(H2O)2(AsW9O34)2]*20H2O with β-alanine. Its structure has been determined by single crystal X-ray diffraction. It crystallizes in the triclinic space group P1, with a=1.196 3(2) nm, b=1.536 5(3) nm, c=1.591 4(3) nm, α=93.97(3)°, β=110.88(3)°, γ=101.07(3)°, V=2.651 8(9) nm3 and Z=1. Least-squares refinement of the structure leads to R and Rw factors of 0.067 3 and 0.162 8, respectively. An unusual structural feature of the compound is that the polyanion [Cu4(H2O)2(AsW9O34)2]10- is linked with the amino-acid complex of Cu2+ by a μ-oxygen atom. 相似文献