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361.
Guy Serratrice Marie-José Stebe Jean-Jacques Delpuech 《Journal of fluorine chemistry》1984,25(3):275-288
Carbon-13 chemical shifts, spin-lattice relaxation times and nuclear Overhauser enhancement factors at 28°C are reported for a series of polyfluoroaliphatic compounds : , and perfluoroalkyl nonionic surfactants CmF2m+1CH2(OC2H4)nOH with m = 6, 7 and n = 3, 4, 5, 6 and C6F13CH2CH2CONH(C2H4O)nH with n = 3, 4. The influence of the perfluoroalkyl group on the 13C chemtcal shifts of the neighbouring hydrogenated carbons is discussed in terms of hyperconjugative type interactions between lone electron pairs on fluorine and the neighbouring CC or CO bond. Relaxation data show similar flexibilities of the fluorinated chains in the different molecules investigated. Nonionic surfactants exhibit segmental motions in both the hydrophobic perfluoroalkyl and the hydrophilic polyoxyethylene chains ; these motions appear to be similar to those of the analogous hydrogenated surfactants. 相似文献
362.
Sultanem C Moutard S Benattar JJ Djedaïni-Pilard F Perly B 《Langmuir : the ACS journal of surfaces and colloids》2004,20(8):3311-3318
We investigate the interfacial behavior of a new type of amphiphilic cyclic oligosaccharide obtained by grafting a phospholipid onto a methylated cyclodextrin. These compounds are able to form stable black foam films, the structure of which can be determined using X-ray reflectivity. These films consist of a highly hydrated bilayer of modified cyclodextrins which are remarkably thick due to their abundant hydration core. In the present paper, we explore the influence of cyclodextrin hydration on the film structure. The hydration rate of the films is tuned by changing the cyclodextrin methylation, by binding the modified cyclodextrins to various molecules (complex formation) and by exposing the films to IR radiation. In addition, we show that the gas permeability of these phospholipidyl-cyclodextrin films is governed by their central layer of bound water, which is an efficient barrier against gas permeation. 相似文献
363.
Prélot B Villiéras F Pelletier M Gérard G Gaboriaud F Ehrhardt JJ Perrone J Fedoroff M Jeanjean J Lefèvre G Mazerolles L Pastol JL Rouchaud JC Lindecker C 《Journal of colloid and interface science》2003,261(2):244-254
In the framework on a study of the acido-basic and sorption properties of iron oxides, a thorough characterization of two types of goethite powders was performed in several laboratories joined in a common project. Chemical analysis by ICPAES; high-resolution SEM, TEM, and AFM observations; XRD with line width analysis; and argon and nitrogen sorption isotherms were used for that purpose. The main crystallographic faces of goethite particles could be identified as {001}, {101}, and {121}, and their abundance correlated with the distribution of low-pressure argon adsorption local isotherms. These results will be very useful for further studies on the relationship between surface reactivity in aqueous solution and orientation of solid surfaces. 相似文献
364.
Thermodynamic study of charge transfert complexes (n-σ*) in solution Charge transfer complexes of quinoline and substituted quinolines (donors) with iodine, iodine chloride, and iodine bromide (acceptors) have been studied spectrophotometrically in CCl4. The 1:1 stoechiometry of these complexes was verified by means of the continous variations method and the appearance of isosbestic points. Simultaneous determination of the equilibrium constant and enthalpy of adduct formation was carried out by calorimetry. It was observed for every donor that the equilibrium constants of the complexes studied increase with the strength of the acceptors. A linear correlation between enthalpy of adduct formation and donor strength was obtained only for the complexes Donor ICI. 相似文献
365.
Le Borgne T Rivière E Marrot J Thuéry P Girerd JJ Ephritikhine M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(4):773-783
Attempts to prepare heterobimetallic complexes in which 3d and uranium magnetic ions are associated by means of the Schiff bases H(2)L(i) derived from 2-hydroxybenzaldehyde or 2-hydroxy-3-methoxybenzaldehyde were unsuccessful because of ligand transfer reactions between [ML(i)] (M=Co, Ni, Cu) and UCl(4) that led to the mononuclear Schiff base complexes of uranium [UL(i)Cl(2)]. The crystal structure of [UL(3)Cl(2)(py)(2)] [L(3)=N,N'-bis(3-methoxysalicylidene)-ethylenediamine; py=pyridine] was determined. The hexadentate Schiff base ligand N,N'-bis(3-hydroxysalicylidene)-2,2-dimethyl-1,3-propanediamine (L) was useful for the synthesis of novel trinuclear complexes of the general formula [[ML(py)](2)U] (M=Co, Ni, Zn) or [[CuL(py)]M'[CuL]] (M'=U, Th, Zr) by reaction of [M(H(2)L)] with [M'(acac)(4)] (acac=MeCOCHCOMe). The crystal structures of the Co(2)U, Ni(2)U, Zn(2)U, Cu(2)U, and Cu(2)Th complexes show that the two ML fragments are orthogonal, being linked to the central actinide ion by the two pairs of oxygen atoms of the Schiff base ligand. In each compound, the UO(8) core exhibits the same dodecahedral geometry, and the three metals are linear. The magnetic study indicated that the two Cu(2+) ions are not coupled in the Cu(2)Zr and Cu(2)Th compounds. The magnetic behavior of the Co(2)U, Ni(2)U, and Cu(2)U complexes was compared with that of the Zn(2)U derivative, in which the paramagnetic 3d ion was replaced with the diamagnetic Zn(2+) ion. A weak antiferromagnetic coupling was observed between the Ni(2+) and the U(4+) ions, while a ferromagnetic interaction was revealed between the Cu(2+) and U(4+) ions. 相似文献
366.
Ying Wang Monique Ponelle Jean-Jacques Sanglier Barbara Wolff 《Helvetica chimica acta》1997,80(7):2157-2167
As one of the regulatory gene products in the HIV-1 genome, Rev protein must be translocated from the nucleus to the cytoplasm to exert its function. Therefore, inhibition of Rev protein translocation could be a useful target for HIV therapy. An extract from the Streptomyces strain A92-308902 with very potent inhibitory activity was found in the course of a high throughput screening with a Rev translocation assay (RTA). Bioassay-guided fractionation with gel filtration, normal-phase and reversed-phase chromatography yielded six RTA-active metabolites belonging to the leptomycin family, the known leptomycin A ( 1 ), leptomycin B ( 2 ), kazusamycin B ( 3 ), and kazusamycin A ( 4 ). and the hitherto unknown dilactonmycin ( 5 ) and delactonmycin ( 6 ), together with an inactive cyclic hexadepsipeptide L-156,620 ( 7 ). The structures were established mainly by spectroscopic methods (UV, FT-IR, FAB-MS, 1H-NMR, 13C-NMR(JMOD), DQ-COSY, ROESY, HSQC, and HMBC). The configuration of all C?C bonds of 1–6 was unambiguously established by analysis of coupling constants and ROESY spectra. All isolated leptomycins 1–6 inhibit Rev translocation at nanomolar concentrations. Six derivatives ( 2a–c and 4a–c ) of leptomycin B ( 2 ) and kazusamycin A ( 4 ) were also prepared and tested in the RTA for preliminary investigations on structure-activity relationships. 相似文献
367.
Ramiro Díaz Anglica Francois AnaMaría Leiva Brbara Loeb Ester Norambuena Mauricio Yaez 《Helvetica chimica acta》2006,89(6):1220-1230
A series of tricarbonyl rhenium(I) complexes of the type fac‐[ReI(CO)3(ppl)(L)]0/+, where ppl is pyrazino[2,3‐f][1,10]phenanthroline, and where L is Cl?, TfO?, 4‐(tert‐butyl)pyridine (tBu‐py), 4‐methoxypyridine (MeO‐py), 4,4′‐bipyridyl (bpy), or 10‐(picolin‐4‐yl)phenothiazine (pptz), were synthesized and fully characterized. In all complexes, an increment in the electron‐acceptor properties of ppl compared to the free ligand was observed. This effect was more significant for pyridine‐type ligands, especially for pptz, compared to Cl? or TfO?. The properties of fac‐[Re(CO)3(ppl)(pptz)]PF6 were compared with those of the analogous compound fac‐[Re(CO)3(dppz)(pptz)]PF6, where dppz is dipyrido(3,2‐a : 2′,3′‐c)phenazine, the goal being to generate long‐lived excited charge‐transfer (CT) states. In this respect, fac‐[Re(CO)3(ppl)(pptz)]PF6 seems to be a promising candidate. 相似文献
368.
Ren M. Williams Luisa De Cola Frantisek Hartl Jean-Jacques Lagref Jean-Marc Planeix Andr De Cian Mir Wais Hosseini 《Coordination chemistry reviews》2002,230(1-2):253-261
The synthesis, solution and solid state structural characterization, photophysical and electrochemical properties of two redox forms of an electrochromic copper-bis(4,4′-dimethyl-6,6′-diphenyl-2,2′-bipyridine) complex, [Cu(3)2]n (n=+1, +2), are presented. Both complexes were characterized in the solid state by X-ray diffraction methods on single-crystals showing that both forms exist in a pseudo-tetrahedral coordination, and a comparison with other structures was made. Like most copper(I) complexes, the red [Cu(3)2]+ complex shows a rather weak emission (Φem=2.7×10−4, dichloromethane). The lifetime of the emitting MLCT state is 34±1 ns, as observed with time resolved emission, and transient absorption (in deoxygenated dichloromethane). Typical emission and transient absorption spectra are presented. The transient absorption spectra indicate that the MLCT state absorbs stronger than the ground state, which is relatively uncommon for metal bipyridine complexes, i.e. no ground state bleaching is observed. The green [(3)2Cu]2+ complex does not show any observable emission or transient absorption, which is a common feature for Cu(II) complexes of this type. The electronic absorption spectra of the chemically and electrochemically produced copper(I/II) complexes are identical. The repeated electrochemical conversion of the Cu(I) center into Cu(II) and vice versa does not cause any decomposition. This is consistent with a fully reversible Cu(I)/Cu(II) redox couple in the corresponding cyclic voltammogram, (E1/2 (Cu(I)/Cu(II))=+0.68 V vs. SCE=+0.23 V vs. Fc/Fc+). These observations indicate that no large structural reorganization occurs upon electrochemical timescales (sub second), and that the different ways of generating the complexes does not effect their final structure, apart from the small differences observed in the X-ray structures of both forms. These characteristics make these complexes rather well suited for their incorporation into an electrochromic display configuration. 相似文献
369.
Jean-Jacques Aaron Mihaela Buna Cyril Parkanyi Maged Shafik Antonious Alphonse Tine Lamine Cisse 《Journal of fluorescence》1995,5(4):337-347
The electronic absorption and fluorescence spectra of coumarin and 11 substituted coumarins were measured in several solvents (dioxane, ethyl ether, ethyl acetate, ethanol, dimethylformamide, acetonitrile, and dimethyl sulfoxide). Ground-state dipole moments were determined in dioxane at 298 K. The results were used to obtain the first excited singlet-state dipole moments of the coumarins under study by the solvatochromic shift method (Bakhshiev, Kawski-Chamma-Viallet, McRae, and Suppan correlations). Also, the ground- and the first excited singlet-state dipole moments were calculated using a combination of the PPP method (-contribution) and the vector sum of the -bond and group moments (-contribution). In general, the first excited singlet-state dipole moments of the coumarins are noticeably higher than the corresponding ground-state values, indicating a substantial redistribution of the-electron densities resulting in a more polar excited state. There is a reasonably good agreement between the calculated and the experimental dipole moments.Presented, in part, at the 2nd International Conference on Solar Energy Storage and Applied Photochemistry, Cairo, Egypt, January 6–11, 1993. For a preliminary communication, see Ref. 1. 相似文献
370.