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91.
The surface species resulting in exposing of the ZSM-5 zeolite at elevated temperatures to methanol, deuterated methanol or ethylene have been studied by IR method.The three-step adsorption at 150°, 300°, 420° C or one-step adsorption at 420° C have been carried out in order to prepare the samples for IR. In all cases the most prominent band appeared in the range 1495–1515 cm?1; besides two bands at about 1470 and 1370 cm?1 have been observed. On the basis of Greenler's results and of the shift values of the bands in our spectrum of adsorbed deuterated methanol it was supposed that the band 1495–1515 cm?1 is due to the OCO group from the surface species. Moreover these species would involve both oxygen atoms from the surface of zeolite but not from OH groups of methanol. 相似文献
92.
Yockot D Moreau V Demailly G Djedaïni-Pilard F 《Organic & biomolecular chemistry》2003,1(10):1810-1818
The synthesis of branched beta-cyclodextrins substituted with mannosyl mimetic derivatives at one primary hydroxy group is described. It was shown that the self-inclusion phenomenon observed for the target compounds in water did not preclude the inclusion properties of the cyclodextrin moiety. 相似文献
93.
Linde C Koliaï N Norrby PO Akermark B 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(11):2568-2573
The substrate electronic effects on the selectivity in the catalytic epoxidation of para-substituted cis stilbenes 2a-i were investigated by using (R,R)-[N,N'-bis(3,5-di-tBu-salicylidene)-1,2-cyclohexanediamine]manganese(III) chloride 1 in benzene as the catalyst with iodosobenzene as the terminal oxidant. A Hammett study of the selectivity results reveals a stronger electrophilic character than previously assumed in the (salen)Mn-catalyzed reaction. In general, the best correlations with the experimental values were obtained by using the Hammett sigma + values, which gave rho = -1.37 for the rate of cis-epoxide formation and rho = -0.43 for the rate of the stepwise process leading to the corresponding trans product. The reaction involves two separate pathways as indicated also by the competitive breakdown of the intermediate on the path to trans epoxide for methoxy-substituted substrates. The asynchronicity in the concerted pathway leading to cis epoxide is apparent for 4-methoxy-4'-nitrostilbene, which yields cis epoxide with 75% ee entirely as a result of electronic effects. 相似文献
94.
The [Ru(bipy)(2)(1)](PF(6))(2) (bipy refers to 2,2'-bipyridine) complex, comprising a ruthenium(II) tris(2,2'-bipyridine) luminophore covalently linked to a di[(o-triethyleneglycoxy)phenyl]amine crown ether 1, has been synthesized and fully characterized. The photophysical properties of this metal complex have been examined in solution at ambient temperature. Luminescence from the metal complex is enhanced significantly in the presence of various adventitious cations, including protons. In particular, Li(+) cations bind to the crown ether, as evidenced by (1)H NMR and luminescence spectroscopy. Cation binding serves to decrease the rate of reductive quenching of the triplet state of the metal complex, thereby increasing the extent of luminescence. The solution-phase conformation of [Ru(bipy)(2)(1)](PF(6))(2), with and without encapsulated Li(+), has been examined by 2-D NMR and by molecular dynamics simulations. 相似文献
95.
Frédérique Malbec René Milcent Patrick Vicart Anne Marie Bure 《Journal of heterocyclic chemistry》1984,21(6):1769-1774
Thirty new 2-substituted-4-amino-5-alkyl or aryl-2,4-dihydro-1,2,4-triazol-3-ones and ten 2-substituted-5-alkyl or aryl-4-(5-nitro-2-furfurylidene)amino-2,4-dihydro-1,2,4-triazol-3-ones were synthesized and characterised by their sharp melting points, elemental analysis, ir and 1H nmr spectra. These new derivatives of 5-nitro-2-furaldehyde were screened for their antibacterial activities. Most of the compounds showed good activity against one test organism, Staphylococcus aureus. For a few compounds, C.M.I. ranged from 4 to 8 μg/ml (higher results than nitrofurantoin). 相似文献
96.
97.
Jean Ravez Annie Perron Jean Pierre Chaminade Paul Hagenmuller Loïc Rivoallan 《Journal of solid state chemistry》1974,10(3):274-281
Two series of phases with tetragonal bronze-like structure and composition BaxLi5?2xT5O15 (T = Nb, Ta) have been isolated in the systems BaNb2O6LiNbO3 and BaTa2O6LiTaO3. All these phases show ferroelectric-paraelectric transitions. The Curie temperature increases with the lithium content. The value of TC for Ba2.03Li0.94Nb5O15 is the highest ever observed for this type of structure: the obtained phases are potentially good materials for the harmonic generation of the 0.53-μm radiation. The optical yield of the niobate Ba2.14Li0.71Nb5O15 is about 2.5 times that of Ba2NaNb5O15 and 250 times that of the K.D.P. The crystallographic and dielectric data of the system Ba2.14Li0.71Nb5O15Ba2.14Li0.71Ta5O15 characterize three domains, which are respectively antiferroelectric, ferroelectric, and paraelectric. The Curie temperature and the optical yield decrease with increasing tantalum content. 相似文献
98.
Isobe H Tanaka T Nakanishi W Lemiègre L Nakamura E 《The Journal of organic chemistry》2005,70(12):4826-4832
The reaction of [60]fullerene with a variety of a secondary aliphatic amines in 20% v/v dimethyl sulfoxide in chlorobenzene under an atmospheric pressure of molecular oxygen allows regioselective introduction of four amino groups and one epoxide group around one pentagon of the fullerene molecule in good to high yield. This new synthesis of tetraaminofullerene expoxide can be carried out with a simple procedure on a multigram scale at room temperature and affords a variety of functionalized fullerene derivatives. Near-infrared analysis of a mixture of [60]fullerene and piperidine in a deaerated dimethyl sulfoxide/chlorobenzene mixture indicated equilibrium formation of [60]fullerene radical anion (C60*-) that persists at least for 2 weeks at room temperature but reacts immediately with molecular oxygen to give the tetraaminofullerene expoxide. The Benesi-Hildebrand analysis of the concentration dependency of the near-infrared absorption indicated that a [C60*- piperidine*+] radical ion pair is formed with an equivalent constant of K = 0.62 +/- 0.02 M(-1) at 25 degrees C. This and other lines of evidence suggest that the oxygenative amination reaction involves C60-mediated reduction of molecular oxygen by the amine. 相似文献
99.
Charbonnière LJ Schurhammer R Mameri S Wipff G Ziessel RF 《Inorganic chemistry》2005,44(20):7151-7160
A new ligand, LC, bis-[(6'-carboxy-2,2'-bipyridine-6-yl)]phenylphosphine oxide, in which the tridentate 6-carboxy-2,2'-bipyridyl arms are directly linked to a phenylphosphine oxide fragment, has been synthesized. The corresponding [Ln.LC]Cl.xH2O complexes (Ln = Eu, x = 4, and Tb, x = 3) were isolated from solutions containing equimolar amounts of LC and hydrated LnCl3 salts and characterized by elemental analysis, mass spectrometry, and infrared spectroscopy. The interactions of the Eu complex with various anions (AMP(2-), ADP3-, ATP,4- HPO4(2-), and NO3-) were studied by titration experiments, using UV-vis, luminescence spectroscopy, and excited-state lifetime measurements. The results are in keeping with strong interactions with the ADP3-, ATP4-, and phosphate anions in TRIS/HCl buffer (0.01 M, pH = 7.0), as revealed by the determination of the conditional stepwise association constants. These values are higher than the one determined for ligand LB, bis[(6'-carboxy-2,2'-bipyridine-6-methyl-yl)]-n-butylamine (Delta log K approximately 1-2). The interaction of complexes [Ln.LB]+ and [Ln.LC]+ with nitrate, monohydrogenophosphate, methyl phosphate (MeP2-), methyldiphosphate (MeDP3-), and methyltriphosphate (MeTP4-) anions was investigated by means of quantum mechanical (QM) calculations. The results, combined with data on the photophysical impact of the sequential competitive binding of anions to the Eu complexes in water, suggest that LB is too flexible to ensure a good coordination pocket, while the molecular structure of ligand LC stabilizes both the formation of the lanthanide complexes and its adducts with ATP. 相似文献
100.
Lemaître F Lucas D Groison K Richard P Mugnier Y Harvey PD 《Journal of the American Chemical Society》2003,125(18):5511-5522
The stoichiometric and catalytic activations of alkyl halides and acid chlorides by the unsatured Pd(3)(dppm)(3)(CO)(2+) cluster (Pd(3)(2+)) are investigated in detail. A series of alkyl halides (R-X; R = t-Bu, Et, Pr, Bu, allyl; X = Cl, Br, I) react slowly with Pd(3)(2+) to form the corresponding Pd(3)(X)(+) adduct and "R(+)". This activation can proceed much faster if it is electrochemically induced via the formation of the paramagnetic species Pd(3)(+). The latter is the first confidently identified paramagnetic Pd cluster. The kinetic constants extracted from the evolution of the UV-vis spectra for the thermal activation, as well as the amount of electricity to bring the activation to completion for the electrochemically induced reactions, correlate the relative C-X bond strength and the steric factors. The highly reactive "R(+)" species has been trapped using phenol to afford the corresponding ether. On the other hand, the acid chlorides react rapidly with Pd(3)(2+) where no induction is necessary. The analysis of the cyclic voltammograms (CV) establishes that a dissociative mechanism operates (RCOCl --> RCO(+) + Cl(-); R = t-Bu, Ph) prior to Cl(-) scavenging by the Pd(3)(2+) species. For the other acid chlorides (R = n-C(6)H(13), Me(2)CH, Et, Me, Pr), a second associative process (Pd(3)(2+) + RCOCl --> Pd(3)(2+.....)Cl(CO)(R)) is seen. Addition of Cu(NCMe)(4)(+) or Ag(+) leads to the abstraction of Cl(-) from Pd(3)(Cl)(+) to form Pd(3)(2+) and the insoluble MCl materials (M = Cu, Ag) allowing to regenerate the starting unsaturated cluster, where the precipitation of MX drives the reaction. By using a copper anode, the quasi-quantitative catalytic generation of the acylium ion ("RCO(+)") operates cleanly and rapidly. The trapping of "RCO(+)" with PF(6)(-) or BF(4)(-) leads to the corresponding acid fluorides and, with an alcohol (R'OH), to the corresponding ester catalytically, under mild conditions. Attempts were made to trap the key intermediates "Pd(3)(Cl)(+)...M(+)" (M(+) = Cu(+), Ag(+)), which was successfully performed for Pd(3)(ClAg)(2+), as characterized by (31)P NMR, IR, and FAB mass spectrometry. During the course of this investigation, the rare case of PF(6)(-) hydrolysis has been observed, where the product PF(2)O(2)(-) anion is observed in the complex Pd(3)(PF(2)O(2))(+), where the substrate is well-located inside the cavity formed by the dppm-Ph groups above the unsatured face of the Pd(3)(2+) center. This work shows that Pd(3)(2+) is a stronger Lewis acid in CH(2)Cl(2) and THF than AlCl(3), Ag(+), Cu(+), and Tl(+). 相似文献