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1.
Medrano F Calderón A Yatsimirsky AK 《Chemical communications (Cambridge, England)》2003,(15):1968-1970
Glycine and N,N-dimethylglycine stabilize La(III) hydroxide complexes of the type La2L2(OH)4 which possess phosphodiesterolytic activity close to that observed with most active tetravalent cations like Ce(IV). 相似文献
2.
Katherine Yu. Bezsoudnova Anatoly K. Yatsimirsky 《Reaction Kinetics and Catalysis Letters》1997,62(1):63-69
α- and β-Cyclodextrins accelerate the Smiles rearrangement of 4-nitrophenyl salicylate which proceeds through the mechanism
of intramolecular aromatic nucleophilic substitution. The binding and catalytic rate constants were calculated from the dependences
of the observed pseudo-first-order rate constants of the rearrangement reaction on cyclodextrin concentration obtained at
various pH values. The catalysis was interpreted in terms of a tighter binding of the anionic, highly delocalized δ-complex
intermediate than that of the substrate to cyclodextrins. 相似文献
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A series of organotin(IV) compounds R3Sn(A) where R = Me or Ph and A is a chromogenic nitrophenolate ligand were prepared and studied as possible colorimetric sensors for anions (F−, Cl−, Br−, AcO−, H2PO4−). Equilibrium constants for a complete set of reactions between R3Sn(A) with A = 2‐amino‐4‐nitrophenolate (ANP) or 4‐nitrophenolate and anions (X−) involving formation of complexes R3Sn(A)(X)− and substitution products R3Sn(X) and R3Sn(X)2− were determined by UV‐vis and 1H NMR titrations in MeCN and DMSO. The binding selectivity was AcO− > F− > H2PO4− > Cl− ≫ Br− in both solvents and both for R = Me and Ph with higher affinity for R = Ph. Compounds with A = ANP were found to have the optimum properties as anion sensors allowing optical detection of F−, AcO− and H2PO4− anions in the 5–100 µM range by appearance of an intense absorption band of free ANP resulting from its substitution with the analyte. Selectivity and affinity of anion interactions with R3Sn(ANP) are similar to those for thiourea receptors, but the organotin receptor produces a much larger naked eye detected optical signal, operates equally well in nonpolar and polar solvents and tolerates the presence of up to 20% vol. of water in DMSO. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
5.
The hydroperoxide anion cleaves unactivated amides and peptides although it is completely unreactive toward ethyl esters. The cleavage by HO2(-) proceeds faster than by OH(-) and involves additional routes with general acid assistance by H2O2 and general base assistance by OH(-) and HO2(-). Cleavage of polypeptides occurs at the N-terminal peptide bond. [reaction: see text] 相似文献
6.
Yatsimirsky V. K. Boldyreva N. A. Lisnyak V. V. Slobodyanik N. S. 《Journal of Thermal Analysis and Calorimetry》2000,62(2):551-554
The thermal stability of sample Mo(PO3)3 that is the initial material for novel catalysts for carbonmonoxide oxidation has been studied. It has been concluded that
molybdenum(III) methaphosphate is stable up to 435°C. Processes of partial oxidation and layering of specimens are determined.
Novel material based on partial oxidized Mo(PO3)3 gives significant rise of the carbon oxidation rate. The molybdenum(III) metaphosphate is of a definite interest in view
of its application in practice as initial material for new catalysts row formation with different content of Mo(PO3)3 and MoOPO4 layers.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
Budarin V. L. Clark J. H. Gorlova A. A. Boldyreva N. A. Yatsimirsky V. K. 《Journal of Thermal Analysis and Calorimetry》2000,62(2):349-352
Mesoporous activated carbons and silica gel (Kieselgel 100, Merck) were modified as follows: (i) treatment with vinyltrimethoxysilane;
or (ii)chlorination with CCl4 followed by the reaction with a Grignard reagent. Modification of silica gel was proved by methods FTIR, NMR-13C and element analysis on carbon. The chemical modification of coals by alkans and olefins was supported by comparison of
results of thermogravimetry for modified coals and modified silica gels. Polymerization of vinyl groups on carbon surface
is shown by methods thermogravimetric analysis and differential scanning calorimetry.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
Oleksenko L. P. Yatsimirsky V. K. Belyakova L. A. Boldureva O. Yu. 《Journal of Thermal Analysis and Calorimetry》2000,62(2):389-394
The thermal stability of metal complexes immobilized on the surface of silica and its connection with the catalytic activity
in the oxidation of hydrogen were investigated. High catalytic activity was exhibited by heterogenized platinum and palladium
acetylacetonate near room temperatures in the initial state and by γ-aminopropylsilicas treated with platinum and palladium
complexes. The catalytic activity of the metal complexes correlates with their thermal stability and with the ability to undergo
oxidation to a metal state with high valence.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Neutral aqueous solutions of cerium ammonium nitrate obtained by dilution of their acetonitrile stock solution with imidazole buffer show high catalytic activity in the hydrolysis of bis(p-nitrophenyl) phosphate (BNPP) and better reproducibility than other similar systems, but suffer from low stability. The kinetics of catalytic hydrolysis is second-order in Ce(IV), independent of pH in the range 5-8 and tentatively involves the Ce2(OH)7+ species as the active form. Attempts to stabilize the active species by different types of added ligands failed, but the use of Ce(IV) complexes pre-synthesized in an organic solvent with potentially stabilizing ligands as precursors of active hydroxo species appeared to be more successful. Three new Ce(IV) complexes, [Ce(Phen)2O(NO3)2], [Ce(tris)O(NO3)(OH)] and [Ce(BTP)2(NO3)4].2H2O (BTP = bis-tris propane, 1,3-bis[tris(hydroxymethyl)methylamino]propane), were prepared by reacting cerium ammonium nitrate with the respective ligands in acetonitrile and were characterized by analytical and spectroscopic techniques. Aqueous solutions of these complexes undergo rapid hydrolysis producing nearly neutral polynuclear Ce(IV) oxo/hydroxo species with high catalytic activity in BNPP hydrolysis. Potentiometric titrations of the solutions obtained from the complex with BTP revealed the formation of Ce4(OH)15+ species at pH > 7, which are protonated affording Ce4(OH)14(2+) and then Ce4(OH)13(3+) on a decrease in pH from 7 to 5. The catalytic activity increases strongly on going to species with a higher positive charge. The reaction mechanism involves first- and second-order in catalyst paths as well as intermediate complex formation with the substrate for higher charged species. 相似文献