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1.
Shekappa D. Lamani Praveen N. Naik Sharanappa T. Nandibewoor 《Journal of solution chemistry》2010,39(9):1291-1310
The kinetics of the osmium(VIII) (Os(VIII)) catalyzed oxidation of diclofenac sodium (DFS) by diperiodatocuprate(III) (DPC)
in aqueous alkaline medium has been studied spectrophotometrically at a constant ionic strength of 1.0 mol⋅dm−3. The reaction showed first order kinetics in [Os(VIII)] and [DPC] and less than unit order with respect to [DFS] and [alkali].
The rate decreased with increase in [periodate]. The reaction between DFS and DPC in alkaline medium exhibits 1:2 [DFS]:[DPC]
stoichiometry. However, the order in [DFS] and [OH−] changes from first order to zero order as their concentration increases. Changes in the ionic strength and dielectric constant
did not affect the rate of reaction. The oxidation products were identified by LC-ESI-MS, NMR, and IR spectroscopic studies.
A possible mechanism is proposed. The reaction constants involved in the different steps of the mechanism were calculated.
The catalytic constant (K
C) was also calculated for Os(VIII) catalysis at the studied temperatures. From plots of log 10
K
C versus 1/T, values of activation parameters have been evaluated with respect to the catalytic reaction. The activation parameters with
respect to the slow step of the mechanism were computed and discussed, and thermodynamic quantities were also determined.
The active osmium(VIII) and copper(III) periodate species have been identified. 相似文献
2.
The protonation of lactate has been studied in a variety of electrolyte solutions using microcalorimetry to reveal a distinct
medium influence imposed on the thermochemistry of the equilibrium. The thermochemistry of lactate protonation, when studied
directly in 1.0 mol⋅L−1 sodium lactate, agreed well with the studies performed in trifluoromethanesulfonate (triflate). This thermodynamic agreement
suggests that the physical chemistry of lactate in the solutions applicable to the TALSPEAK process—a solvent extraction method
for separating trivalent actinides from trivalent lanthanides within the scope of used nuclear fuel processing efforts—may
be simulated in triflate solutions. Potentiometry, spectrophotometry and microcalorimetry have been subsequently used to study
the thermodynamic features of neodymium and americium complexation by lactate using triflate as a strong background electrolyte.
Three successive mononuclear lactate complexes were identified for Nd(III) and Am(III). The stability constants for neodymium,
β
101=2.60±0.01, β
102=4.66±0.02 and β
103=5.6±0.1, and for americium, β
101=2.60±0.06, β
102=4.7±0.1 and β
103=6.2±0.2, were found to closely agree with the thermodynamic studies reported in sodium perchlorate solutions. Consequently,
the thermodynamic medium effect, imposed on the TALSPEAK-related solution equilibria by the presence of strong background
electrolytes such as NaClO4 and NaNO3, does not significantly impact the speciation in solution. 相似文献
3.
Andrea Bencini Antonio Bianchi Silvia Del Piero Claudia Giorgi Andrea Melchior Roberto Portanova Marilena Tolazzi Barbara Valtancoli 《Journal of solution chemistry》2008,37(4):503-517
The coordination features of a polyaza macrocycle, containing the diverse bipyridine unit 4,4′-(2,5,6,11,14-pentaaza[15]-[15](2,2′)-bipyridylophane
(L3), with Co(II) and Cd(II) have been studied in aqueous solution and in the aprotic solvent dimethylsulfoxide (DMSO). The study
was carried out at 298 K by means of potentiometric, spectrophotometric and calorimetric techniques. The formation of the
dinuclear species M2
L3 is observed for Co(II) both in water and in DMSO, whereas Cd(II) is able to form this type of dinuclear complex only in DMSO.
The FT-IR spectra of the mononuclear species ML3, formed in both solvents, provide evidence that the rigid structure of the polyaminic chain prevents metal ions from being
coordinated by all of the nitrogens of the macrocyclic cavity, in good agreement with the behavior suggested by the thermodynamic
parameters. The results are compared with those for the complexation of Co(II) and Cd(II) with similar polyazamacrocycles
containing a bipyridine unit directly inside the cavity. Semi-empirical calculations were also performed to obtain structural
information. 相似文献
4.
5.
Haruko Ikeuchi Mitsuhiro Kanakubo Shin Okuno Rika Sato Koichi Fujita Manatsu Hamada Nobuhiro Shoda Kenta Fukui Koji Okada Hikaru Kanazawa Akira Iimori Daisaku Miyake Takeshi Takeda Gen P. Satô 《Journal of solution chemistry》2010,39(10):1428-1453
The densities and the viscosities of tris(acetylacetonato)cobalt(III) solutions in acetonitrile, dichloromethane, chloroform, tetrachloromethane, benzene, toluene, ethylbenzene, and p-xylene were measured in the dilute concentration regions at several temperatures ranging from 278 to 313 K under ambient pressure. The partial molar volumes of the solvents and solute were calculated. They are independent of concentration and increase slightly as the temperature increases. The viscosity A- and B-coefficients of the Jones-Dole equation were obtained. The A-coefficients were found to be zero within experimental error. The B-coefficients are positive and decrease as the temperature increases. Thermodynamic quantities of activation for viscous flow were calculated on the basis of Eyring’s viscosity equation. From the quantities obtained in this study, along with some information from the literature, it is suggested that structure-making interactions occur between the segments of the complex and the solvent molecules. These interactions include electrostatic interactions between the local charge on the complex and the dipole moment of the solvent in solutions of acetonitrile and dichloromethane, interlocking packing interactions along C 3-axis of the complex with solvent in solutions of chloroform and tetrachloromethane, and π-electron interactions between the chelate ring of the complex and the solvent in solutions of benzene, toluene, ethylbenzene, and p-xylene. 相似文献
6.
Lauren E. Manck Christopher R. Benson Andrew I. Share Hyunsoo Park Amar H. Flood 《Supramolecular chemistry》2014,26(3-4):267-279
Self-assembled 2 × 2 grids have been characterised as high-fidelity species produced when the correct stoichiometric ratios are met, but rarely are the individual steps leading to and from their formation characterised. Here, we present such a study using equilibrium-restricted factor analysis to model a set of UV–vis spectra starting from a bis-bidentate ligand to the assembly of a 2 × 2 grid complex upon titration with 1 equiv. of [Cu(MeCN)4](PF6) and to disassembly upon further titration. Intermediate species [CuL2]+, [Cu2L3]2+, [Cu3L2]3+ and [Cu2L]2+ are evidenced along the assembly and disassembly pathways. Complementary 1H NMR titrations are consistent with the rich set of complexes and equilibria involved. Given the nature of the assembly process, the assembly is entropy driven and likely enthalpy driven as well. The disassembly process is both enthalpy and entropy driven according to the standard free energy values derived from the modelling of the spectrophotometric titration data. 相似文献
7.
M. Asha Jhonsi A. Kathiravan G. Paramaguru C. Manivannan R. Renganathan 《Journal of solution chemistry》2010,39(10):1520-1530
Fluorescence quenching of [Ru(bpy)3]2+ by a series of organic dyes has been investigated by using the steady state fluorescence technique in aqueous medium. The
dyes used are anthraquinone dyes: uniblue, acid blue 129, alizarin, alizarin red S and the azo dyes: congo red, sunset yellow,
methyl orange, tartrazine, acid orange 63, methyl red and erichrome black T. The quenching of [Ru(bpy)3]2+ was found to obey the Stern-Volmer equation and the corresponding Stern-Volmer plots were linear indicating dynamic quenching.
The quenching rate constants (k
q) were calculated from the fluorescence data. The mechanism of quenching was discussed on the basis of the quenching rate
constants as well as the reduction potential of dyes. The electron transfer mechanism has been proved by the calculation of
Gibbs energy changes (ΔG
et) by applying the Rehm-Weller equation. 相似文献
8.
Interactions of Arsenazo III with Nd(III) in aqueous solutions (pH range 3 to 4) were studied using a spectrophotometric method.
Some discrepancies are present in literature concerning the concentrations of the prevailing species and their composition.
Threshold bootstrap computer-assisted target factor analysis (TB CAT) was applied to the evaluation of UV-VIS spectra of Arsenazo
III in aqueous solutions containing varying amounts of neodymium(III) ions. The thus obtained experimental data are interpreted
with consideration of the measurement uncertainties affecting this system. Within the limits of resolution of the experimental
method, two complexes NdAazo and Nd(Aazo)2 were indicated in the studied pH range. The values of formation constants for log 10
β
11 fall in the range 4.9 to 6.3 and for log 10
β
12 fall between 10.5 and 12.1. 相似文献
9.
Tsuneo Okubo 《Colloid and polymer science》2013,291(7):1623-1629
Distorted colloidal crystal suspension of similar-sized aggregates of diamonds (1.5 μm in diameter) was obtained by the deionization of aqueous suspension of the pre-particles of diamond, 4 nm in diameter. The stability, characteristics, and the rigidity of the crystal-like suspensions were studied. The main cause for the formation of the similar-sized aggregates is deduced to be the cooperation between the van de Waals inter-particle attraction and the repulsion induced by the vigorous thermal motion of the pre-particles. The rigidity was evaluated from the microscopic observation in the sedimentation equilibrium. Fluctuation parameters of the distorted colloidal crystals estimated from the rigidities were between 0.03 and 0.06, which are quite similar to those of typical colloidal crystals and solids of hard spheres. 相似文献
10.
Cyclic linear-sweep voltammetry was used to study the complexation of Sc(III), Ga(III), In(III) and Ln(III) with eriochrome
red B (ERB). It was established that all metal ions investigated form complex compounds with azodye having a mole ratio, M(III):ERB =
1:2. The hydroxo forms of M(III) ions, which take part in interaction with ERB, were determined by the Nazarenko method. The
stability constants for the formation of these chelates are nearly the same. It was shown that the reduction of the ligand
in the complex does not only depend on the peculiarities of complexation, but the processes occurring in pre-electrode layer
also influence it. 相似文献
11.
Almeida LM Farani PG Tosta LA Silvério MS Sousa OV Mattos AC Coelho PM Vasconcelos EG Faria-Pinto P 《Natural product research》2012,26(22):2137-2143
Eremanthus erythropappus (DC) McLeisch, a plant popularly known as Candeia (Asteraceae), has high therapeutic potential. In this study, the in?vitro schistosomicidal potentials of the ethanolic, dichloromethane and hexane extract of branches were evaluated. Couples of worms obtained from the infected mice were cultured in RPMI supplemented with foetal bovine serum and antibiotics. Four pairs of adult worms were exposed to increasing concentrations of each extract and examined by light microscope. The extracts at 100 and 200?μg?mL(-1) had schistosomicidal activity, as demonstrated by the analysis of several aspects such as tegument darkening, absence of motility, incapacity of adhesion in culture plate and absence of egg in culture medium. At 50 and 75?μg?mL(-1), the dichloromethane and hexane extracts were highly effective. The results suggest that these extracts could be useful in the development of new schistosomicidal drugs. 相似文献
12.
Tsuneo Okubo 《Colloid and polymer science》2013,291(8):1887-1893
Macroscopic and microscopic drying patterns were observed on a cover glass, a watch glass, and a Petri glass dish during the course of dryness of aqueous suspensions of similar sized aggregates of diamonds (CD1), which formed from the deionization of the pre-particles of diamond 4 nm in diameter. Two kinds of macroscopic patterns, i.e., outer and inner broad rings, and spoke lines were formed. Cooperative drying processes of the convection, sedimentation, and solidification were clarified. Microscopic drying patterns showing the formation of very large dendritic aggregates from the CD1 particles were observed only when the excess amount of sodium chloride higher than 2 mM coexisted in the initial suspensions before dryness and further initial CD1 concentration is lower than 0.17 wt%. 相似文献
13.
Jovita Mendoza-Barrón Araceli Jacobo-Azuara Roberto Leyva-Ramos Ma. Selene Berber-Mendoza Rosa Ma. Guerrero-Coronado Laura Fuentes-Rubio J. Merced Martínez-Rosales 《Adsorption》2011,17(3):489-496
In this study a surfactant-modified zeolite (SMZ) was prepared by adsorbing the cationic surfactant hexadecyltrimethylammonium
(HDTMA) bromide on a clinoptilolite. The adsorption of the surfactant modified the surface properties of the clinoptilolite
and enhanced the anionic capacity of the SMZ. The adsorption equilibrium data of As(V) from the water solution on the SMZ
were obtained in a batch adsorber, and the Langmuir isotherm matched the data reasonably well. The As(V) adsorption capacity
of the SMZ was 12.5 times greater than that of the clinoptilolite. The adsorption of As(V) on SMZ was mainly due to the interactions
between the anionic sites of the SMZ and the As(V) anions in water solution. The adsorption capacity of the SMZ was dependent
on the solution pH. The adsorption capacity was increased and decreased by augmenting the pH from 5 to 7 and from 7 to 12,
respectively. This unusual behavior was due to the fact that the affinity of the As(V) for the SMZ was dependent on the As(V)
species that were present in solution. The adsorption capacity of the SMZ was slightly favored by decreasing the temperature
from 25 to 15 °C. The heat of adsorption was estimated to be ΔH
ads=−46.82 KJ/mol, indicating that the adsorption was exothermic and the As(V) was chemisorbed on the SMZ. 相似文献
14.
Complexes of copper(II) with a number of polyphosphate and polymetaphosphate anions have been studied in aqueous solutions
by potentiometric, spectroscopic and theoretical methods. Stability constants of the complexes have been determined as well
as their coordination modes. Results of the equilibrium studies provided evidence for the formation of ML, MHL and ML(OH)
x
type complexes with the ligands studied. The length of the polyphosphate chain was found to affect the oxygen atom charge
that is reflected in the stability constants of the ML type complexes. Moreover, the stability of the complex is also influenced
by the spatial arrangement of the phosphate groups in phosphates and metaphosphates. The spectral parameters observed for
certain complexes have permitted us to deduce the inner coordination sphere of the studied complexes. 相似文献
15.
Yonit Sembira-Nahum Alexander Apelblat Emanuel Manzurola 《Journal of solution chemistry》2008,37(3):391-401
Densities of aqueous solutions of L-glutamic acid and magnesium-L-glutamate were determined from T=288.15 to 333.15 K at 5 K temperature intervals. The measured densities were used to evaluate the apparent molar volumes,
V
2,φ
(m,T), the cubic expansion coefficients, α(m,T), and the changes of isobaric heat capacities with respect to pressure, (∂
C
p
/∂
p)
T,m
. They were qualitatively correlated with changes in the structure of water that occur when L-glutamic acid or magnesium-L-glutamate
are present. 相似文献
16.
Jyothi C. Abbar Shekappa D. Lamani Sharanappa T. Nandibewoor 《Journal of solution chemistry》2011,40(3):502-520
The oxidation of amitriptyline by potassium permanganate has been investigated spectrophotometrically in the presence of ruthenium(III)
as catalyst in aqueous acidic medium at a constant ionic strength of 0.20 mol⋅dm−3. The stoichiometry was found to be 1:1 in terms of the mole ratio of amitriptyline and permanganate ions consumed. The order
of the reaction with respect to manganese(VII) and ruthenium(III) concentration was unity while the order with respect to
amitriptyline was less than unity over the concentration range studied. The rate increased with an increase in acid concentration.
The reaction rates revealed that the Ru(III) catalyzed reaction was about eight-fold faster than the uncatalyzed reaction.
The oxidation products were identified by spectral analysis. A tentative mechanism consistent with the kinetics has been proposed.
The reaction constants involved in the different steps of the reaction mechanism were calculated. Kinetic experiments suggest
that HMnO4 is the reactive permanganate species and [Ru(H2O)6]3+ is the reactive Ru(III) species. 相似文献
17.
Maria Lalia-Kantouri Christos D. Papadopoulos Antonios G. Hatzidimitriou Stavroula Skoulika 《Structural chemistry》2009,20(2):177-184
The reaction of Fe(III) with the substituted salicylaldehydes [X-saloH, where X = 3-OCH3 (L 1 ), 5-CH3 (L 2 ), 5-Cl (L 3 ), 5-NO2 (L 4 )] led to the formation of four new iron(III) hetero-heptanuclear complexes (Fe–Na) under the general formula [Fe2(X-salo)8Νa5] · 3OH · zH2Ο. The two different coordination modes of the ligand, as well as the geometry around the metal ions were deduced by X-ray structure analysis of compound 1, [Fe2(3-OCH3-salo)8Νa5] · 3OH · 8H2Ο. The complexes have also been characterized by physicochemical and spectroscopic (IR, UV–Vis, Mössbauer) methods. 相似文献
18.
Ahmed A. El-Sherif 《Journal of solution chemistry》2010,39(10):1562-1581
Formation equilibria of cobalt(II) complexes of 2-(aminomethyl)-benzimidazole (AMBI) and the ternary complexes Co(AMBI)L (L = aliphatic or aromatic dicarboxylic acids) were investigated in aqueous solutions at 25?°C and 0.1 mol?dm?3 ionic strength. Stoichiometry and stability constants are reported for the complexes formed. The speciation of the complexes was resolved. Values of $\log_{10}\ (K_{\mathrm{Co(AMBI)L}}^{\mathrm{Co(AMBI)}})$ and Δlog?10 K are calculated and discussed. The effect of chelate ring size of the dicarboxylic acid complexes on their stability constants was examined. The effect of temperature on the dissociation constant of AMBI, CBDCA, and the formation constant of Co(AMBI) and Co(AMBI)-CBDCA complexes was studied and the thermodynamic parameters were calculated. Formation of the metal complexes has been found to be spontaneous, exothermic and entropically favorable. The solid complexes of [Co(AMBI)L] (L = oxalic acid, 1,1-cyclobutanedicarboxylic acid (CBDCAH2) and malonic acid) have been synthesized and characterized by elemental analysis, infrared, spectra, magnetic and conductance measurements. Electronic spectra and μ eff values suggest a tetrahedral geometry for Co(II)-complexes. The isolated metal chelates have been screened for their antibacterial activities and the complexes show a significant antibacterial activity against Pseudomonas fluorescence (Gram ?ve) and Bacillus subtilis (Gram +ve). The activity increases at higher concentration of the compounds. 相似文献
19.
By means of the hybrid exchange–correlation functionals, as it is implemented in the CRYSTAL computer code, ab initio calculations for main ABO3 perovskite (0 0 1) surfaces, namely SrTiO3, BaTiO3, PbTiO3, CaTiO3, SrZrO3, BaZrO3, PbZrO3 and CaZrO3, were performed. For ABO3 perovskite (0 0 1) surfaces, with a few exceptions, all atoms of the upper surface layer relax inward, all atoms of the second surface layer relax outward, and all third layer atoms, again, inward. The relaxation of (0 0 1) surface metal atoms for ABO3 perovskite upper two surface layers for both AO and BO2-terminations, in most cases, are considerably larger than that of oxygen atoms, what leads to a considerable rumpling of the outermost plane. The ABO3 perovskite (0 0 1) surface energies always are smaller than the (0 1 1) and especially (1 1 1) surface energies. The ABO3 perovskite AO and BO2-terminated (0 0 1) surface band gaps always are reduced with respect to the bulk values. The B–O chemical bond population in ABO3 perovskite bulk always are smaller than near the (0 0 1) and especially (0 1 1) surfaces. 相似文献
20.
《Journal of Coordination Chemistry》2012,65(22):3999-4006
Co(II) and Cu(II) complexes and metal-free t-butylphenyl peripherally substituted porphyrazine (Pz) have been screened for in vitro antifungal (Aspergillus niger) and antioxidant (free radical scavenging, superoxide radical scavenging, and reducing power) activities. The results were compared with synthetic antioxidants, e.g., butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), trolox, or α-tocopherol. The free radical scavenging activity of H2Pz was higher than the CuPz complex. However, CuPz complex showed higher superoxide radical scavenging activity than BHA, BHT, and trolox while H2Pz and CoPz showed weaker activity than BHA, BHT, and trolox. The reducing power of all complexes was similar to that of BHT and α-tocopherol on a per molar basis. The ligand and complexes have antifungal activity against A. niger. The compounds have significant superoxide radical scavenging activity against various antioxidant systems in vitro. 相似文献