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41.
Margarita Valero Silvia M. B. Costa José R. Ascenso M. Mercedes Velázquez Licesio J. Rodríguez 《Journal of inclusion phenomena and macrocyclic chemistry》1999,35(4):663-677
The inclusion of the anti-inflammatory drug, Nabumetone, in -, - and hydroxypropyl--cyclodextrin (CDs) is studied using UV-VIS absorption and steady-state fluorescence emission. Binding constants and thermodynamic parameters of complex formation are determined by spectrofluorimetry. The inclusion phenomena of Nabumetone with the three cyclodextrins is compared with that of the well known similar anti-inflammatory drug Naproxen. In the case of Nabumetone pronounced differences are observed in the complexation process with each cyclodextrin whereas the respective Naproxen complexes are nearly identical. 1H-NMR experiments show that the inclusion process in Nabumetone can occur either through the substituents in the -2 (butanone) or -6 (methoxy) positions in the naphthalene ring. 相似文献
42.
Composite membranes were prepared by (a) infiltrating NAFION with SiO2-P2O5-ZrO2 sol, and (b) recasting a film using NAFION solution containing SiO2-P2O5-ZrO2 sol. The membranes were characterized by Differential Thermal Analysis and ac-impedance spectroscopy as a function of relative humidity. The influences of the heat treatment (80°C–150°C) and cleaning on the electrical properties were investigated. The incorporation of SiO2-P2O5-ZrO2 gels into NAFION lead to improvements in its thermal stability and proton conductivity. 相似文献
43.
Hiromi Matsuhashi Masakazu Oikawa Hiromi Shibata Michiko Tanaka 《Reaction Kinetics and Catalysis Letters》1998,65(2):253-258
Reversible formation of F+-centers was observed over platinum promoted sulfated zirconia in the presence and absence of hydrogen. The intensity of ESR
signal of F+-centers was increased by treatment in He stream and it was decreased rapidly by supply of hydrogen in gas phase. This behavior
seems to be related to proton spillover. 相似文献
44.
Laura León-Reina 《Journal of solid state chemistry》2007,180(4):1250-1258
La9.75□0.25(Ge6O24)O2.62 oxy-apatite shows a phase transition from triclinic to hexagonal symmetry at approximately 1020 K that has been characterised by high-temperature synchrotron X-ray and neutron powder diffraction, and ionic conductivity measurements. The crystal structure at 1073 K has been determined from joint Rietveld refinements of synchrotron X-ray and neutron powder diffraction data. The study shows that hexagonal-La9.75□0.25(Ge6O24)O2.62 contains interstitial oxygen at the position previously reported for other oxy-germanates. Changes in the oxide conductivity associated with this structural transition are discussed. The thermal analyses showed a weight loss on heating close to 600 K very likely due to water release. The synchrotron thermodiffractometric study shows an anomaly in the cell parameters evolution at that temperature, which indicates that this residual water is located into the apatite channels. The electrical characterisation under different atmospheres (dry and wet synthetic air) indicates that there is a significant proton contribution to the overall conductivity below 600 K, mainly under wet atmosphere. 相似文献
45.
Gostev F. E. Petrukhin A. N. Titov A. A. Shienok A. I. Marevtsev V. S. Sarkisov O. M. 《Russian Chemical Bulletin》2003,52(3):557-561
Intramolecular processes in electronic-excited states of 2,4,5-triarylimidazole molecules were studied by femtosecond laser spectroscopy. Experiments were carried out with two types of compounds, namely, those experiencing intramolecular proton transfer and two model compounds in which it is impossible. Schemes of the processes studied were proposed and the characteristic rate constants were determined. The excited-state intramolecular proton transfer (ESIPT) in the molecules with planar structure of the reaction center is a very fast process (100 fs). If the reaction center has a nonplanar structure and, hence, the intramolecular hydrogen bond is weakened, the ESIPT time is determined by the time of conformational rearrangement of the molecule. 相似文献
46.
The experimental values of the gas-phase proton affinities for a variety of 4-substituted benzonitriles, 4-substitutedN, N-dimethylanilines, and 4-substituted benzaldehydes have been examined by means of correlation analysis techniques and by ab initio quantum mechanical methods (MP2/ 6-31G(d) level). From this study it is concluded that in the gas phase, 4-(dimethylamino)-benzonitrile essentially protonates on the dimethylamino group, while protonated 4-cyanobenzaldehyde is very nearly a 21 mixture of the carbonyl- and cyano-protonated forms.This work is dedicatedin memoriam to Professor Robert W. Taft. 相似文献
47.
48.
M.E. Kletskii A.A. Millov A.V. Metelitsa M.I. Knyazhansky 《Journal of photochemistry and photobiology. A, Chemistry》1997,110(3):857-270
The mechanism of light-induced transformation in the salicylideneaniline molecule was studied by semiempirical PM3 calculations. The structures and energies of the minima and saddle points (transition states) on the S0, S1 and T1 potential energy hypersurfaces (PESs) were obtained, together with the gradient lines on the PESs. The structure-energy scheme was compared with the experimental findings. According to the results obtained, the following principle processes are observed: fast S1 excited state intramolecular proton transfer (ESIPT), followed by typical ESIPT fluorescence; the formation of two S1 twisted intramolecular charge transfer (TICT) structures which quench the ESIPT fluorescence; the diabatic formation of two ground state metastable coloured “post-TICT” structures responsible for photochromism. 相似文献
49.
Dr. Pradip Ghosh Sander de Vos Dr. Martin Lutz Dr. Frederic Gloaguen Prof. Dr. Philippe Schollhammer Dr. Marc-Etienne Moret Prof. Dr. Robertus J. M. Klein Gebbink 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(55):12560-12569
Homogeneous electrocatalytic proton reduction is reported using cobalt complex [ 1 ](BF4)2. This complex comprises two bis(1-methyl-4,5-diphenyl-1H-imidazol-2-yl)methane (HBMIM ) ligands that contain an acidic methylene moiety in their backbone. Upon reduction of [ 1 ](BF4)2 by either electrochemical or chemical means, one of its HBMIM ligands undergoes deprotonation under the formation of dihydrogen. Addition of a mild proton source (acetic acid) to deprotonated complex [ 2 ](BF4) regenerates protonated complex [ 1 ](BF4)2. In presence of acetic acid in acetonitrile solvent [ 1 ](BF4)2 shows electrocatalytic proton reduction with a kobs of ≈200 s−1 at an overpotential of 590 mV. Mechanistic investigations supported by DFT (BP86) suggest that dihydrogen formation takes place in an intramolecular fashion through the participation of a methylene C−H bond of the HBMIM ligand and a CoII−H bond through formal heterolytic splitting of the latter. These findings are of interest to the development of responsive ligands for molecular (base)metal (electro)catalysis. 相似文献
50.
脂肪族胺、醇和醚的气相质子亲合能(PA)与N, O原子所带电荷(qx)以及烷基的极化效应指数(PEI)的关系可表示为其中a、b、c为系数。回归分析结果表明, 上式较好地表达了脂肪族胺、醇和醚的气相碱性变化规律。 相似文献