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排序方式: 共有77条查询结果,搜索用时 15 毫秒
1.
Summary Complexation equilibria of the Tl(I) ion with 18-crown-6 and dibenzo-18-crown-6 were studied polarographically in 10 nonaqueous solvents. The stability of the complexes is strongly influenced by the nature of solvents and varies with their Lewis basicities. It has been found that the logK
s value (K
s is the stability constant of the complex) can be well described by empirical relation logK
s=a DN+b, whereDN stands for the Gutmann donor number anda andb mark the regression coefficient. Addition of the second explanatory parameter, the acceptor number, is not statistically significant. This result is in agreement with the predominant role of Tl(I) ion solvation.
Elektrochemische Untersuchungen von Tl(I)-Kronenetherkomplexen in nichtwäßrigen Medien
Zusammenfassung Es wurden die Komplexierungsgleichgewichte des Tl(I)-Ions mit 18-Krone-6 und Dibenzo-18-krone-6 polarographisch in 10 nichtwäßrigen Lösungsmitteln untersucht. Die Stabilität der Komplexe wird sehr stark vom Solvens beeinflußt, wobei eine starke Abhängigkeit von der Lewis-Basizität beobachtet wird. Es wurde festgestellt, daß die logK s-Werte (K s ist die Komplexstabilitätskonstante) gut mit der empirischen Beziehung logK s=a DN+b beschrieben werden können, wobeiDN die Gutmann'sche Donorzahl unda undb die Regressionskonstanten bedeuten. Hinzunahme der Akzeptorzahl als zweiten Parameter bleibt statistisch insignifikant. Dieses Ergebnis stimmt mit dem dominierenden Einfluß der Tl(I)-Ionensolvatation überein.相似文献
2.
Alan P. Marchand Anna Hazlewood Zilin Huang Satish Kumar Vadlakonda John-David R. Rocha Trevor D. Power Kata Mlinarić-Majerski Lada Klaić Goran Kragol Jeffrey C. Bryan 《Structural chemistry》2003,14(3):279-288
Bis-cage-annulated 18-crown-6 and 20-crown-6 macrocyclic ethers (i.e., 1 and 2, respectively) have been synthesized, and their alkali metal picrate extraction profiles have been determined. Host system 1 proved to be a significantly more avid alkali metal cation complexant than 2 and somewhat more avid than 18-crown-6. Both 1 and 18-crown-6 display modest selectivity toward K+ and Rb+. A stable host–guest complex was prepared by slow evaporation of a CH2Cl2–hexane solution of an equimolar mixture of 2 and potassium picrate. The X-ray crystal structure of this complex reveals that picrate anion functions as a bidentate ligand therein. The gas-phase interaction energy between the 2 K+ complex and picrate anion was calculated to be ca. –64.9 kcal mol–1, thereby indicating that participation of picrate anion as an additional bidentate ligand results in significant stabilization of complex 10. 相似文献
3.
Ewa Lada Xiubin Lei Marek K. Kalinowski 《Monatshefte für Chemie / Chemical Monthly》1992,123(5):425-433
Summary The formation constants,K
S, of the 18-crown-6 complex with thallium(I) ion were studied by polarographic measurements in binary mixtures of acetonitrile, acetone, tetrahydrofuran, and dimethylsulfoxide with water, as a function of the solvent mole fraction. In all the cases, the variation of the stability constant can be described by the empirical relation logK
S=a[(–1)/(2+1)]+b where stands for relative permittivity of a given mixture anda andb mark the regression coefficients. The values ofa calculated for four series of binary mixtures showed correlation with the Gutmann donor numbers of the neat organic solvents which form the mixture.On leave from the Department of Chemistry, Jingzhou Teacher's College, Jingzhou, Hubei, China 相似文献
4.
Galina A. Gazieva Yurii B. Vikharev Lada V. Anikina Tatyana B. Karpova Angelina N. Kravchenko Evgenii A. Permyakov Igor V. Svitanko 《Mendeleev Communications》2013,23(4):202-203
Target synthesis of substituted thioglycolurils possessing sedative activity predicted by preliminary 3D-QSAR simulation of bioactive structures has been carried out. 相似文献
5.
Prof. Dr. Andrei V. Malkov Dr. Sigitas Stončius Dr. Mark Bell Dr. Fabiomassimo Castelluzzo Dr. Pedro Ramírez‐López Dr. Lada Biedermannová Prof. Dr. Vratislav Langer Dr. Lubomír Rulíšek Prof. Dr. Pavel Kočovský 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(28):9167-9185
Detailed kinetic and computational investigation of the enantio‐ and diastereoselective allylation of aldehydes 1 with allyltrichlorosilanes 5 , employing the pyridine N‐oxides METHOX ( 9 ) and QUINOX ( 10 ) as chiral organocatalysts, indicate that the reaction can proceed through a dissociative (cationic) or associative (neutral) mechanism: METHOX apparently favors a pentacoordinate cationic transition state, while the less sterically demanding QUINOX is likely to operate via a hexacoordinate neutral complex. In both pathways, only one molecule of the catalyst is involved in the rate‐ and selectivity‐determining step, which is supported by both experimental and computational data. 相似文献
6.
Vrbková Eva Sekerová Lada Vyskočilová Eliška Zapletal Martin Červený Libor 《Research on Chemical Intermediates》2022,48(4):1403-1421
Research on Chemical Intermediates - Several types of modified zeolite BETA38 with different iron loading were prepared. Prepared materials were characterized using different techniques (XRD, XRF,... 相似文献
7.
Zoi G. Lada Amaia Soto Beobide Georgios N. Mathioudakis George A. Voyiatzis 《Molecules (Basel, Switzerland)》2021,26(1)
Polymeric composites constitute an appealing class of materials with applications in various fields. Spin crossover (SCO) coordination complexes are switchable materials with potential use in data storage and sensors. Their incorporation into polymers can be considered an effective method for their wider practical application. In this study, Fe(II) SCO/polylactic acid hybrid polymeric composites have been prepared by film casting. The mononuclear coordination complex [Fe{N(CN)2}2(abpt)2] was incorporated into polylactic acid. The morphological, structural and thermoanalytical characterization of the composite films were performed via scanning electron microscopy (SEM), attenuated total reflectance (ATR/FTIR), Raman spectroscopy and differential scanning calorimetry (DSC). In addition, the migration release study (MRS) of the SCO compound from the polymeric matrix into the food simulant 50% v/v water/ethanol solution was also examined via UV/Vis absorption. Of particular interest was the investigation of the SCO behavior of the coordination complex after its incorporation into the polymer matrix; it was accomplished by temperature-dependent micro-Raman spectroscopy. The described attempt could be considered a preparatory step toward the development of SCO-based temperature sensors integrated into food packaging materials. 相似文献
8.
Tomasz Smolinski Danuta Wawszczak Andrzej Deptula Wieslawa Lada Tadeusz Olczak Marcin Rogowski Marta Pyszynska Andrzej Grzegorz Chmielewski 《Journal of Radioanalytical and Nuclear Chemistry》2017,313(1):69-77
A micro-cloud point extraction method was discussed for preconcentration and spectrophotometric quantification of U(VI). The method depends on complex formation between U(VI) and 2-(4-sulphophenyloazo)-1,8-dihydroxy-3,6-naphtalenedisulphonic acid (SPADNS) at pH 7.0 and subsequent extraction of the complex in a mixed surfactant medium (cethyltrimethyl ammonium bromide and Triton X-114). The separation was carried out in the presence of 1% Na2SO4 at room temperature. The calibration curve was linear up to 3000 µg L?1. The enrichment factor, detection limit and precision were 16.0, 1.05 µg L?1, and 2.3%, respectively. The method was employed for the determination of U(VI) in real samples with different matrices. 相似文献
9.
AbstractIn recent years the electro-optic polymers emerged as an important branch of material science. This growth and interest is fundamentally motivated by practical application of these materials in second-order nonlinear optics and in waveguiding configuration. Indeed, these materials marry excellent optical quality of amorphous σ bonded polymers with enhanced first hyperpolarizability of imbedded organic nonlinear optical molecules. Although a big progress was achieved with them, concerning particularly the science, understanding and applications, some problems remain still incompletely solved, particularly the stability of induced polar order by the application of external electric field and the molecule aggregation. In this review paper we recall techniques of thin film fabrication, poling, characterization of NLO properties and discuss more precisely problems of molecule aggregation as well as the temporal decay of polar order. A novel 3D second-order NLO chromophores, namely the [2] paracyclophanes, which may help to limit the aggregation, are proposed. We show, in particular, that this molecule can be poled in doped PMMA thin films. Practical applications of electro-optic polymers are also reviewed and discussed. 相似文献
10.
Magdalini Lada 《代数通讯》2013,41(11):4306-4323
Let Λ be an artin algebra with representation dimension equal to three and M an Auslander generator of Λ. We show how, under certain assumptions, we can mutate M to get a new Auslander generator whose endomorphism ring is derived equivalent to the endomorphism ring of M. We apply our results to selfinjective algebras with radical cube zero of infinite representation type, where we construct an infinite set of Auslander generators. 相似文献