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991.
Pantarotto D Briand JP Prato M Bianco A 《Chemical communications (Cambridge, England)》2004,(1):16-17
Functionalised carbon nanotubes are able to cross the cell membrane and to accumulate in the cytoplasm or reach the nucleus without being toxic for the cell up to 10 [micro sign]M. 相似文献
992.
The kinetics of the inversion of configuration of a family of chiral oxonium ions, that is, O-protonated 1-aryl-1-methoxyethanes [YMe+], were investigated in two different gaseous media (in CH3X with X=F and X=Cl) at 720 torr of pressure and in the temperature range: 25-140 degrees C. The activation parameters of the [YMe+] inversion reaction were found to obey two different isokinetic relationships (IKR), depending on the nature and the position of the substituents in the oxonium ions and on the nature of the bulk gas employed. The observation of two IKR for the same family of reactions was related to a switchover in the resonant vibrational energy exchange between the reactants' critical mode, active in the transition state (omega), and the discrete vibrational levels v of the bulk gas. In CH3F, this vibrational-vibrational coupling switchover concerns the out-of-plane C-F...H-O bending) the phi family) and the H3C-F stretching (the gamma family) modes in the proton-bound [CH3F.YMe+] complex. In CH3Cl, the coupling switchover concerns the out-of-plane C-Cl...H-O bending (the phi family) and the H3C-Cl methyl group rocking (the gamma family) modes in the proton-bound [CH3Cl.YMe+] complex. The [YMe+] activation dynamics also determine the inversion dynamics. The [YMe+]ret<==>[YMe+]inv isomerization for the phi family involves the same "thermodynamically most favorable" transition state in both the CH3F and the CH3Cl media, whereas the same process for the gamma family proceeds through different, dynamically favored transition states. 相似文献
993.
Boiocchi M Bonizzoni M Fabbrizzi L Foti F Licchelli M Taglietti A Zema M 《Dalton transactions (Cambridge, England : 2003)》2004,(4):653-658
The nickel(II) complex with an open chain tetramine containing a piperazine fragment (1) displays an unusual resistance to demetallation in acidic solution and exhibits a lifetime of about five minutes in a solution 0.1 M in HClO4 and 7.0 M in NaClO4. Sluggishness with respect to the demetallation is ascribed to the occurrence of the boat-to-chair conformational conversion of the piperazine fragment, which implies the passage through the highly energetic half-boat transition state. The use of a high concentration of the inert electrolyte induces a 'salting out' effect on both thermodynamics (stability of metal complexes is enhanced) and kinetics (resistance to demetallation is increased). 相似文献
994.
Tegoni M Dallavalle F Belosi B Remelli M 《Dalton transactions (Cambridge, England : 2003)》2004,(9):1329-1333
The equilibria of copper(II) with (S)-glutamic-gamma-hydroxamic acid (H2L) were investigated in aqueous solution by different techniques: glass electrode potentiometry; calorimetry; VIS and CD spectrophotometry; and ES-MS. An unexpected pentacopper(II) 12-metallacrown-4 [Cu5L4H(-4)](2-) was detected, analogous to those well known formed by alpha- and beta-aminohydroxamic acids, but of lower stability. Another five species were found: [CuLH]+; [CuL2H2]; [Cu2L2]; [CuL2H]-; and [CuL2]2-. Their structures are proposed based on both spectroscopic and calorimetric data. 相似文献
995.
Tagmatarchis N Arcon D Prato M Shinohara H 《Chemical communications (Cambridge, England)》2002,(24):2992-2993
High-resolution 13C NMR has been used to structurally characterize a single isomer possessing C2 molecular symmetry as well as an inseparable mixture of other isomers of [92]fullerene, produced from dysprosium arc-burned soot, separated and isolated via multi-stage recycling HPLC. 相似文献
996.
[reaction: see text] The reaction of the vinyl oxirane 1 derived from D-glucal with a series of O-nucleophiles (alcohols, phenol, and diacetone D-glucose) affords the corresponding 2-unsaturated beta-O-glycosides in a completely stereoselective way (syn 1,4-addition pathway). Epoxide 1 is generated in situ by treatment of the corresponding hydroxy mesylate 2 with t-BuOK in anhydrous benzene. 相似文献
997.
Maurizio Guerra Derek Jones Francesco Paolo Colonna Giuseppe Distefano Alberto Modelli 《Chemical physics letters》1983,98(5):522-526
The intensity of the shake-up satellites present in the solid-phase XPS spectra of paranitroaniline (1), 2-amino-5-nitropyridine (2) and 2-amino-5-nitropyrimidine (3) decreases from (1) to (3) in agreement with CNDO/S CI calculations. The HOMO—LUMO energy gap appears to be responsible for the observed trend. 相似文献
998.
999.
Full quantitative multiple-scattering analysis of X-ray absorption spectra: application to potassium hexacyanoferrat(II) and -(III) complexes 总被引:1,自引:0,他引:1
Hayakawa K Hatada K D'Angelo P Della Longa S Natoli CR Benfatto M 《Journal of the American Chemical Society》2004,126(47):15618-15623
A recently developed method to the full quantitative analysis of the XAS spectra extending from the absorption edge to the high-energy region is presented. This method is based on the use of two independent approaches to the analysis of the EXAFS and XANES data, the well-known GNXAS and the newly developed MXAN procedures. Herein, we report the application of this technique to two iron complexes of known structure where multiple-scattering effects are prominent, the potassium hexacyanoferrat(II) and -(III) crystals and aqueous solutions. The structural parameters obtained from refinements using the two methods are equal and compare quite well with crystallographic values. Small discrepancies between the experimental and calculated XANES spectra have been observed, and their origin has been investigated in the framework of non-muffin-tin correction. The ligand dependence of the theoretical spectra has been also examined. Analysis of the whole energy range of the XAS spectra has been found to be useful in elucidating both the type of ligands and the geometry of iron sites. These results are of particular use in studying the geometrical environment of metallic sites in proteins and complexes of chemical interest. 相似文献
1000.
Conoci S Guldi DM Nardis S Paolesse R Kordatos K Prato M Ricciardi G Vicente MG Zilbermann I Valli L 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(24):6523-6530
Thin films consisting of a fulleropyrrolidine derivative 1 and a novel water-soluble porphyrin 2 were prepared by the Langmuir-Sh?fer (LS, horizontal lifting) method. In particular, a solution of 1 in chloroform and dimethyl sulfoxide was spread on the water surface, while porphyrin 2 (bearing peripheral anionic groups) was dissolved into the aqueous subphase. To the best of our knowledge, such a versatile method of film fabrication for fullerene/porphyrin mixed composite films has never been used before. Evidence of the effective interactions between the two moieties at the air-water interface was obtained from the analysis of the floating layers by means of surface pressure versus area per molecule Langmuir curves, Brewster angle microscopy and UV-visible reflection spectroscopy. The characterisation of the LS films by UV-visible spectroscopy reveals that the two constituents behave as discrete and weakly interacting pi systems. The use of polarised light suggests the existence of a preferential direction of the macrocyclic rings with an edge-on arrangement with respect to the substrate surface. Finally, photoaction spectra were recorded from films deposited by only one horizontal lifting onto indium-tin-oxide (ITO) electrodes and the observed photocurrent increased notably with increasing transfer surface pressure. 相似文献