共查询到20条相似文献,搜索用时 27 毫秒
1.
A.K. Singh Puja Saxena Amit Panwar 《Journal of inclusion phenomena and macrocyclic chemistry》2006,54(3-4):299-305
Copper (II) complex of 2,4-dimethyl-1,5,9,12-tetraazacyclopentadeca-1,4-diene, [Me2(15)dieneN4] was synthesized and used in the fabrication of Cu2+ – selective ISE membrane in PVC matrix. The membrane having Cu(II) macrocyclic complex as electroactive material along with sodium tetraphenyl borate (NaTPB) as anion discriminator. Dibutyl phthalate (DBP) as plasticizer in poly(vinyl chloride) (PVC) matrix was prepared for the determination of Cu2+. The best performance was observed by the membrane having Cu(II) complex–PVC–NaTPB–DBP with composition 1:5:1:3. The sensor worked well over a concentration range 1.12 × 10−6 M–1.0 × 10−1 M between pH 2.1–6.2 and a fast response time 10±2 s and a lifetime of 6 months. Their performance in partially non-aqueous medium was found satisfactory. Electrodes exhibited excellent selectivity for Cu2+ ion over other mono-, di-, trivalent cations. It can also be used as indicator electrode in the potentiometric titration of Cu2+ against EDTA as well as in the determination of Cu2+ in real samples. 相似文献
2.
Michael A. Beckett Martin P. Rugen-Hankey K. Sukumar Varma 《Journal of Sol-Gel Science and Technology》2006,39(2):95-101
The reaction of metaborate esters (RO)3B3O3 [R = Me, Et, ClCH2CH2–, Cl3CCH2–, ClCH2CH2CH2–, (ClCH2)2CH–] with Si(OR)4 (R = Me, Et), either neat or in dry propan-2-one or dry THF at room temperature, led to gels which when dried and heated
in air for 20 mins at 600°C afforded borosilicate glasses in high ceramic yields. The dried gels and glasses were characterized
by elemental analysis, TGA, IR, and powder XRD, and solid-state MAS 29Si and 11B NMR. The gelling reaction was investigated by solution 11B and 29Si NMR. These NMR studies indicated B–O–Si reaction intermediates and a mechanism involving alkoxy exchange and various condensation/elimination
reactions of the borosilicate esters have been proposed. 相似文献
3.
Mehdi Taghdiri Mohammad Kazem Rofouei Mojtaba Shamsipur 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(1-2):181-186
The complexation reactions between dibenzo-24-crown-8 (DB24C8) and K+, Rb+, Cs+ and Tl+ ions were studied conductometrically in different acetonitrile–nitromethane mixtures at various temperatures. The formation
constants of the resulting 1:1 complexes were calculated from the computer fitting of the molar conductance–mole ratio data
at different temperatures. At 25 °C and in all solvent mixtures used, the stability of the resulting complexes varied in the
order Tl+ > K+ > Rb+ > Cs+. The enthalpy and entropy changes of the complexation reactions were evaluated from the temperature dependence of formation
constants. It was found that the stability of the resulting complexes increased with increasing nitromethane in the solvent
mixture. The TΔS° vs. ΔH° plot of all thermodynamic data obtained shows a fairly good linear correlation indicating the existence
of enthalpy–entropy compensation in the complexation reactions. 相似文献
4.
Lenoble V Garnier C Masion A Ziarelli F Garnier JM 《Analytical and bioanalytical chemistry》2008,390(2):749-757
This work allowed the characterization of the Cd-binding sites of two compounds taken as models for exudates, the main components
of soil organic matter (SOM). The studied compounds were exopolysaccharides (EPS), specifically exudates of roots (polygalacturonic
acid) and of soil bacteria (Phytagel). Potentiometric acid–base titrations were performed and fitting of the obtained results
indicated the presence of two main classes of acidic sites, defined by their pK
a values, for both EPS but of a different nature when comparing the two compounds. The two studied exopolysaccharides presented
different acidic/basic site ratios: 0.15 for Phytagel and 0.76 for polygalacturonic acid. Spectroscopic techniques (13C/113Cd NMR, FTIR) distinguished different Cd surroundings for each of the studied EPS, which is in agreement with the titration
results. Furthermore, these analyses indicated the presence of –COOH and –OH groups in various proportions for each exopolysaccharide,
which should be linked to their reactivity towards cadmium. Cadmium titrations (voltammetric measurements) also differentiated
different binding sites for each compound and allowed the determination of the strength of the Cd-binding site of the EPS.
Fitting of the results of such voltammetric measurements was performed using PROSECE (Programme d’Optimisation et de Speciation Chimique dans l’Environnement), a software coupling chemical speciation calculation and binding parameter optimization. The fitting, taking into account
the Cd2+/H+ competition towards exopolysaccharides, confirmed the acid-base titrations and spectroscopic analyses by revealing two classes
of binding sites: (i) one defined as a strong complexant regarding its Cd2+–EPS association (logK = 9–10.4) and with basic functionality regarding H+–EPS association (pK
a = 11.3–11.7), and (ii) one defined as a weak complexant (logK = 7.1–8.2) and with acidic functionality (pK
a = 3.7–4.0). Therefore the combination of spectroscopic analyses, voltammetry, and fitting allowed the precise characterization
of the binding sites of the studied exopolysaccharides, mimicking the main SOM components. Furthermore, the binding parameters
obtained by fitting can be used in biogeochemical models to better define the role of key SOM compounds like exudates of roots
and of soil bacteria on trace metal transport or assimilation. 相似文献
5.
The lactone 20R-25-norcycloartan-3β,6α,16β-triol-20,24-olide was synthesized from cyclosiversigenin.
Presented at the 1st International Symposium on Edible Plant Resources and the Bioactive Ingredients, Xinjiang, China, July
25–27, 2008.
Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 324–327, May–June, 2009. 相似文献
6.
Gholam Hossein Rounaghi Massoumeh Mohajeri Shima Ashrafi Hoda Ghasemi Saman Sedaghat Maryam Tavakoli 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(1-2):1-6
Conductance measurements are reported for nickel(II), cupper(II), silver(I) and cadmium(II), salts in acetonitrile (AN)–dimethylformamide
(DMF) binary solvents containing macrocyclic ligand, 1,10-dibenzyl-1,10-diaza-18-crown-6 (DBDA18C6) at different temperatures.
The changes in molar conductance caused by addition of DBDA18C6 to solutions were analyzed by non-linear least squares to
give stability constants of 1:1 metal cation–DBDA18C6 complexes. The results show that the stabilities of the complexes are
sensitive to solvent composition and in some cases the sequence of stabilities is changed with changing the composition of
the mixed solvents. The values of thermodynamic quantities (ΔH°c and ΔS°c) for formation of DBDA18C6-Ni2+, DBDA18C6-Cu2+, DBDA18C6-Ag+ and DBDA18C6-Cd2+ complexes were obtained from temperature dependence of the stability constants and the results show that the values of ΔH°c and ΔS°c for these complexes are sensitive to the nature and composition of AN–DMF binary solutions, but they do not vary monotonically
with the solvent composition. 相似文献
7.
The new cycloartane glycoside cycloorbicoside D, which has the structure 23ξ,24ξ-cycloartan-3β6α,16β,23,24,25-hexaol 3-O-β-D-xylopyranoside,
was isolated from the aerial part of Astragalus orbiculatus Ledeb. (Leguminosae).
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Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 345–346, July–August, 2005. 相似文献
8.
The photoluminescence properties of xZnO–(100−x)SiO2 (x = 0, 5, 10, 20) containing 1% Eu2O3 prepared by a sol–gel method were systematically investigated. The results indicated that the relative proportion of f–f transitions to charge transfer (CT) absorption decreased with the increase of ZnO concentration. The intensity of 5D0–7FJ transitions of Eu3+ ions was enhanced with the increase of ZnO content due to local structure changes and decreased quantities of Eu3+ ions clusters. The results of fluorescence line narrow (FLN) spectra indicated that Eu3+ ions occupied one site in SiO2 glass and two sites in ZnO–SiO2 glasses. The second-order crystal field parameters were calculated. B20 and B22 for site 1 increased with excitation energy, while ones hardly changed for site 2. 相似文献
9.
Yoon-Ki Joung Hak Soo Choi Tooru Ooya Nobuhiko Yui 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):323-328
We have previously prepared a stimuli-responsive inclusion complex between PEG–b-PEI–g-dextran graft copolymer (PEG–PEI–dex) and γ-cyclodextrin (γ-CD) in order to investigate unique inclusion phenomena, double-axle
inclusion. For further study, a γ-CD derivative, mono-6-O-(2-sulfonato-6-naphthyl)-γ-CD (SN-γ-CD) was additionally synthesized for 1H NMR titration study, which is expected to induce the competition of pendant naphthyl group with external polymer guests.
Consequently, 1H NMR titration results of the inclusion complex of PEG–PEI–dex with SN-γ-CD showed stoichiometric changes, temperature-dependence,
and reversibly pH-responsive properties of the inclusion complexes in terms of chemical shift variation. 相似文献
10.
The direct molecular structure implementations of the gage-including atomic orbital (GIAO), individual gages for atoms in
molecules (IGAIM) and continuous set of gage transformations (CSGT) methods for calculating nuclear magnetic shielding tensors
at both the Hartree-Fock (HF) and density functional (B3LYP) levels of theory with 6-31G(d), 6-311G(d), 6-31++G(d,p), 6-311++G(d,p),
and 6-311++G(df,pd) basis sets are presented. Dependence on the 1H and 13C NMR chemical shifts on the choice of method and basis set have been investigated. Also, these chemical shifts of 2-aryl-1,3,4-oxadiazoles
5a–g have been performed related to dihedral angles (C4–C3–C2–O) of two conformers. The optimized molecular geometries and 1H and 13C chemical shift values of 2-aryl-1,3,4-oxadiazoles 5a–g in the ground state have been obtained. The linear correlation coefficients of 13C NMR chemical shifts for these molecules were given. The new nuclear magnetic shielding tensors of tetramethylsilane (TMS)
were calculated. The data of 2-aryl-1,3,4-oxadiazole derivatives display significant molecular structure and NMR analysis.
Also, these provide the basis for future design of efficient materials having the 1,3,4-oxadiazole core. 相似文献
11.
Gh. H. Rounaghi A. Soleamani K. R. Sanavi 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(1-2):43-48
The complexation reactions between Ag+, Hg2+ and Pb2+ metal cations with aza-18-crown-6 (A18C6) were studied in dimethylsulfoxide (DMSO)–water (H2O) binary mixtures at different temperatures using the conductometric method. The conductance data show that the stoichiometry
of the complexes in most cases is 1:1(ML), but in some cases 1:2 (ML2) complexes are formed in solutions. A non-linear behaviour was observed for the variation of log K
f of the complexes vs. the composition of the binary mixed solvents. Selectivity of A18C6 for Ag+, Hg2+ and Pb2+ cations is sensitive to the solvent composition and in some cases and in certain compositions of the mixed solvent systems,
the selectivity order is changed. The values of thermodynamic parameters (ΔH
co, ΔS
co) for formation of A18C6–Ag+, A18C6–Hg2+ and A18C6–Pb2+ complexes in DMSO–H2O binary systems were obtained from temperature dependence of stability constants and the results show that the thermodynamics
of complexation reactions is affected by the nature and composition of the mixed solvents. 相似文献
12.
Nine compounds including six cycloartane glycosides cyclosieversiosides A, B, F, G, and H and astrasieversianin IX; β-sitosterol, β-sitosterol β-D-glucopyranoside, and D-3-O-methyl-chiro-inositol were isolated and identified from roots of Astragalus sieversianus Pall. (Leguminosae) growing in the Republic of Kyrgyzstan.
Presented at the 6th International Symposium on the Chemistry of Natural Compounds (SCNC, Ankara, Turkey, June 28–29, 2005.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 253–256, May–June, 2008. 相似文献
13.
I. A. Sukhina R. P. Mamedova M. A. Agzamova M. I. Isaev 《Chemistry of Natural Compounds》2007,43(2):159-161
The two trisdesmoside cycloartane glycosides astragaloside VII and cyclotrisectoside were isolated from Astragalus dissectus (Leguminosae) and identified. The latter was 20R,25-epoxy-24S-cycloartan-3β,6α,16β,24-tetraol 3-O-β-D-xylopyranoside-6,24-di-O-β-D-glucopyranoside and was a new natural compound.
Presented at the Sixth International Symposium on the Chemistry of Natural Compounds (SCNC, Turkey, Ankara, 28–29 June 2005).
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 132–134, March–April, 2007. 相似文献
14.
Gholam Hossein Rounaghi Razyeh Sanavi Khoshnood Mohammad Hossein Arbab Zavvar 《Journal of inclusion phenomena and macrocyclic chemistry》2006,54(3-4):247-252
The complexation reactions between Mg2+, Ca2+, Ag+ and Cd2+ metal cations with N-phenylaza-15-crown-5 (Ph-N15C5) were studied in acetonitrile (AN)–methanol (MeOH), methanol (MeOH)–water (H2O) and propanol (PrOH)–water (H2O) binary mixtures at different temperatures using the conductometric method. The conductance data show that the stochiometry of all of the complexes with Mg2+, Ca2+, Ag+ and Cd2+ cations is 1:1 (L:M). The stability of the complexes is sensitive to the solvent composition and a non-linear behaviour was observed for variation of log K
f of the complexes versus the composition of the binary mixed solvents. The selectivity order of Ph-N15C5 for the metal cations in neat MeOH is Ag+>Cd2+>Ca2+>Mg2+, but in the case of neat AN is Ca2+>Cd2+>Mg2+>Ag+. The values of thermodynamic parameters (ΔH
c
o
, ΔS
c
o
) for formation of Ph-N15C5–Mg2+, Ph-N15C5–Ca2+, Ph-N15C5–Ag+ and Ph-N15C5–Cd2+ complexes were obtained from temperature dependence of stability constants and the results show that the thermodynamics of complexation reactions is affected by the nature and composition of the mixed solvents. 相似文献
15.
M. L. Keshtov A. L. Rusanov N. M. Belomoina A. S. Peregudov E. R. Tkhakakhov 《Russian Chemical Bulletin》2005,54(8):1939-1941
New hexaarylbenzene-containing di- and tetrafluoroarenes were prepared by the Diels—Alder reactions of 1,4-bis(1-oxo-2,4,5-triphenylcyclopentadien-3-yl)benzene
with 4-fluoro-4′-(phenylethynyl)- and 4-fluoro-4′-(4-fluorophenylethynyl)benzophenone, respectively.
__________
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1881–1883, August, 2005. 相似文献
16.
SrAl2O4:Eu2+, Dy3+ powders were synthesized by sol–gel–combustion process using metal nitrates as the source of metal ions and citric acid as
a chelating agent of metal ions. The amounts of citric acid in mole were two times those of the metal ions. By tracing the
formation process of the sol–gel, it is found that decreasing the amount of NO3
− in the solution is necessary for the formation of transparent sol and gel, and the dropping of ethanol into the precursor
solution can decrease the amount of NO3
− in the solution. By combusting citrate sol at 600 °C, followed by heating the resultant combustion ash at 1,100–1,300 °C
in a weak reductive atmosphere containing active carbon, SrAl2O4:Eu2+, Dy3+ phosphors can prepared. X-ray diffraction, Thermogravimetry–differential thermal analysis, scanning electron microscopy and
fluorescence spectrophotometer were used to investigate the formation process and luminescent properties of the as-synthesized
SrAl2O4:Eu2+, Dy3+. The results reveal that the SrAl2O4 crystallizes completely when the combustion ash was sintered at 1,200–1,300 °C. The excitation and emission spectra indicate
that excitation broadband mainly lies in a visible range and the phosphors emit strong light at 510 nm under the excitation
of 348 nm. The afterglow of phosphors lasts for over 10 h when the excited source is cut off. 相似文献
17.
A. V. Afonin D. E. Perez M. C. Ruiz de Azua R. H. Contreras P. Lazzeretti 《Russian Chemical Bulletin》1997,46(2):292-296
Participation of the proton in a specific intramolecular C−H...X (X=N, 0) interaction leads to an increase in its geminal1H−1H and1H−31P spin-spin coupling constants (SSCC). According toab initio calculations carried out in the 6–31G** basis set, the observed effect is mainly due to the change in the diamagnetic spin-orbital contribution to SSCC.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 306–309, February, 1997. 相似文献
18.
Guang-hui Cai 《Journal of mathematical chemistry》2006,39(2):243-251
By using a Rosenthal type inequality established in this paper and inspired by Berberan-Santos et al., J. Math. Chem. 37 (2005)
101–115, the complete convergence rates in the strong laws for ρ− - mixing random fields are discussed. The result obtained extends the result of Ko et al., Commun. Korean Math. Soc. 19 (2004)
765–773.
AMS Subject classification: 60F15 相似文献
19.
Liu Yuyan Liu Hongping Guo Yuanqing Liu Xiaoyong Lin Jieli Huang Guangming Gao Hui Li Jinrui 《中国科学B辑(英文版)》2000,43(2):121-128
LMR spectra for v=1←0 transitions of14N16O in X2II1/2, 3/2 states were observed at 5.6 μm and 5.4 μm of CO laser. Introducing the advanced isotopic molecular constant scaling function
to Hund’s case (a) diatomic structure model, these spectra were analyzed and fitted together with all reliable previous spectral
data of14N16O as well as14N17O and14N18O. A full set of precise molecular parameters and their vibrational dependencies have been determined with much higher precision
(1–2 orders for most parameters). Many of them have been obtained for the first time. Using isotopic scaling function, the
molecular constants of14N17O and14N18O were deduced. 相似文献
20.
Sham M. Sondhi Gurudas Bhattacharjee Rafid K. Jameel Rakesh Shukla Ram Raghubir Olivier Lozach Laurent Meijer 《Central European Journal of Chemistry》2004,2(1):1-15
9-Chloro-2,4-(un)substituted acridines (1) on condensation with sulpha- diazine, sulphathiazole, and sulphaacetamide gave
condensation products 3a-h. 3-Aryl-4-phenyl-2-imino-4-thiazolines (4) on condensation with 9-chloro-2,4-(un)substituted acridines
(1) gave condensation products 5a–5o. Both 3a–3h and 5a–5o were purified by crystallization or by chromatography. Structures
assigned to 3a–3h and 5a–5o are supported by correct spectral data. Antiinflammatory and analgesic activity screening of 3a,
3e, 3f and 5a–5c, 5e, 5g, 5i, 5m, 5n were carried out using carrageenin induced paw oedema and phenyl quinone writhing assay.
Some of the compounds exhibited interesting antiinflammatory or analgesic activities. 相似文献