Search results for "aqueous solution"
showing 10 items of 1610 documents
The interaction of organotins with native DNA
1992
The compounds R2SnCl2 and R3SnCl (RMe, Et, nBu, nOct, Ph, in ethanol solution) as well as the aqueous species [Me2Sn(OH2)n]2+ and [Me3Sn(OH2)2]+, react with aqueous native DNA, yielding solid phases. According to the pointcharge model treatment of the 119Sn Mossbauer parameter nuclear quadrupole splitting, trans-octahedral R2Sn(O2PXY)2, and trigonalbipyramidal R3Sn(O2PXY), (RMe, Et, nBu), would occur in the pellets, the tin atoms being coordinated by phosphodiester groups of the nucleic acid. The precipitates from Ph2SnIV would consist of the DNA complex as well as of the Ph2SnIV distannoxane obtained by hydrolysis of the reactant, whilst nOct2SnCl2, nOct3SnCl and Ph3SnCl would mainly yield…
Induced-Fit Molecular Recognition with Water-Soluble Cavitands
2000
Synthesis of novel water-soluble cavitands 1 and 2 and their complexes—the caviplexes—is described. The solubility in water derives from four primary ammonium groups on the lower rim and eight secondary amide groups on the upper rim. Cavitands 1 and 2 exist as D2d velcraplex dimers in aqueous solution but the addition of lipophilic guests 15–24 induces conformational changes to the vase-like structures. The internal cavity dimensions are 8×10 A, and the exchange rates of guests in the caviplexes are slow on the NMR timescale (room temperature and 600 MHz). The direct observation of bound species and the stoichiometry of the complexes is reported. The association constants (Ka) between 0.4×1…
Violurato complexes of nickel(II). Formation equilibria. Deprotonation equilibria of the coordinated ligands and related stereochemical changes
1986
The formation equilibria of nickel(II) violurato-complexes in water and dimethylsulphoxide-water (80∶20) as well as deprotonation of the coordinated ligands and related stereochemical changes are reported. The stability constants of the Ni2+-H2V− complexes logβ1=5.06, Iogβ2=9.38, logβ3=12.98 as well as the acidity constants of the [Ni(H2V)3]− complex, logβj1= 8.37, logβj2=15.76, logβj3=22.37 are determined at 25 °C and 0.1M NaClO4. A new violurato-complex of Ni2+, Na4[Ni(HV)3]5H2O, is isolated and characterized.
Internal Structure and Dynamics of the Decamer D(ATGCAGTCAG) 2 In Li + -H 2 O Solution: A molecular Dynamics Simulation Study
2003
Molecular dynamics simulation of the decamer d(ATGCAGTCAG) 2 in aqueous solution, electroneutralized by Li + ions has been carried out. Emphasis is on the verification of the equilibrium conditions and the related structural and dynamical properties. Applicability of the kinetic part of Boltzmann's H function as a measure of thermodynamic equilibrium is tested. Overall structural stability has been confirmed by different RMSDs. Conformational and helicoidal parameters have been analyzed statistically and dynamically. Dynamical analysis reveals the existence of dynamical sub-states, which typically appear as abrupt changes from a mean level to another in the value of parameter. In statistica…
Hydrothermal growth mechanism of SnO2 nanorods in aqueous HCl
2018
Abstract Rutile-type nanorods of SnO2 were obtained in a one-pot hydrothermal synthesis starting from SnCl4·5H2O and HCl in a temperature range between 200 and 240°C. Although the nanorods are polydisperse, the average length of the nanorods could be adjusted from 13 to 65 nm by varying of the reaction temperature. The resulting anisotropic nanocrystals were characterized using powder X-ray diffraction (PXRD), (high resolution-) transmission electron microscopy (HR-TEM), and selected area electron diffraction (SAED). The particle growth proceeds via a dissolution-recrystallization process with soluble [SnCl5(H2O)]− intermediates, as confirmed by PXRD, Raman spectroscopy, and magic angle spi…
Anhydrous Amorphous Calcium Oxalate Nanoparticles from Ionic Liquids: Stable Crystallization Intermediates in the Formation of Whewellite
2015
The mechanisms by which amorphous intermediates transform into crystalline materials are not well understood. To test the viability and the limits of the classical crystallization, new model systems for crystallization are needed. With a view to elucidating the formation of an amorphous precursor and its subsequent crystallization, the crystallization of calcium oxalate, a biomineral widely occurring in plants, is investigated. Amorphous calcium oxalate (ACO) precipitated from an aqueous solution is described as a hydrated metastable phase, as often observed during low-temperature inorganic synthesis and biomineralization. In the presence of water, ACO rapidly transforms into hydrated whewe…
Properties of mixed colloidal crystals
2007
We prepared colloidal crystals from aqueous suspensions of spherical, charged polystyrene spheres under deionised conditions. Using a home-built multipurpose light scattering apparatus we measured the static structure factor, the static shear modulus and the intermediate scattering function. In addition we also monitored also the conductivity as a function of the composition and the particle number density. For the mixture investigated the data are well described assuming the formation of randomly substituted body-centered-cubic crystals.
Exploring new water soluble bridged dicopper(II) assemblies: Synthesis, structure, spectroscopic characterization, properties, and their interactions…
2021
Abstract Three new water soluble dimetallic copper(II) complexes, [Cu(H2O)5][Cu2(cpdp)(µ-O2As(CH3)2)]2Br2·13.83H2O·0.67CH3OH (1), [Cu2(Hcpdp)(µ-SO4)]·5H2O (2) and [Cu2(cpdp)(µ-pz)]·16H2O (3) (H3cpdp = N,N′-Bis[2-carboxybenzomethyl]-N,N′-Bis[2-pyridylmethyl]-1,3-diaminopropan-2-ol; (CH3)2AsO2− = cacodylate; SO42− = sulfate; pz− = pyrazolate) have been successfully synthesized and characterized for the investigation of coordination/binding aspects with biologically significant monosaccharide, d -glucosamine. Preparation of 1, 2 and 3 has been achieved by carrying out reaction of H3cpdp with stoichiometric quantities of CuCl2·2H2O/NaO2As(CH3)2·3H2O, CuSO4·5H2O and CuCl2·2H2O/1H-pyrazole, respe…
Optimization of the sorption process of copper cations from aqueous solution by pine bark (Pinus sylvestris)
2020
This study examined the effect of the chemical modification of pine bark (Pinus sylvestris) on the sorption efficiency of copper cations. The results were interpreted using pseudo-first order and pseudo-second order reaction models as well as Langmuir and Freundlich isothermal models. The sorption experiments were carried out using the batch technique. The study indicated the effect of the competitive sorption of copper cations and hydrogen cations as well as the adverse effect on the sorption efficiency of copper hydroxides formed under alkaline conditions. The need to assess the measurement uncertainty in determining the basic parameters of the sorption process was indicated. It was also …
Sequestration of organometallic compounds by natural organic matter. binding of trimethyltin(IV) by fulvic and alginic acids
2006
The binding capacity of fulvic and alginic acids towards trimethyl tin(IV) cation was quantitatively determined in order to evaluate the sequestering ability of toxic organometallic compounds by natural organic matter. Investigations were performed in the pH range of natural waters (5–8.5) where the carboxylate groups, largely present in both sequestering agents, are the main binding sites. A chemical interaction model, according to which both the protonation of polyelectrolyte ligands and the hydrolysis of the organotin cation in NaCl aqueous solution were considered, was used to define the speciation of the systems under investigation. Measurements performed at different ionic strength va…