Hydration Of Complexes Research Articles

Highly Enantioselective [3+2] Annulation of Indoles with Quinones to Access Structurally Diverse Benzofuroindolines.

A facile and efficient method to produce optically pure benzofuroindolines, especially those without 3-substituents that are susceptible to rearomatization, through [3+2] annulation of indoles with quinones is described. The suitable combination of a BOX ligand CuII hydrate complex and freshly activated molecular sieves functions to give controllably dynamic release of water, which enables the success of this reaction. This reaction can be performed on a gram scale with only 0.5 mol % catalyst loading.

Influence of Counterions on the Hydration Structure of Lanthanide Ions in Dilute Aqueous Solutions.

A synergic approach combining molecular dynamics (MD) simulations and X-ray absorption spectroscopy (XAS) has been used to investigate diluted (0.1 M) aqueous solutions of two lanthanide ions (Ln3+), namely, La3+ and Dy3+, with triflate, nitrate, and bis(trifluoromethylsulfonyl)imide (Tf2N-) as counterions. The different complexing ability of the three anions has been highlighted by the analysis of the MD simulations: Tf2N- does not form inner-sphere complexes, while a small amount of triflate coordinates both the La3+ and Dy3+ cations in their first solvation shell. On the other hand, the nitrate ion is almost absent in the La3+ first coordination sphere, while forming contact ion pairs with Dy3+. Both lanthanide ions are found to preferentially interact with the water molecules, and the total number of oxygen atoms coordinating the Ln3+ cations in their first solvation sphere is the same in all of the solutions, regardless of whether they belong to water molecules or to the counterion. The presence of counterions in the cation first or second shell changes neither the first shell distance nor the symmetry of the hydration complex formed in solution. The MD results have been confirmed by comparison with the Ln K-edge XAS experimental data, and the quantitative analysis of the extended X-ray absorption fine structure (EXAFS) spectra of the three salt solutions has provided a definite proof of the accuracy of the force field employed in the simulations and of the MD structural result. The anion-water and water-water hydrogen bond lifetimes have been analyzed highlighting the slow down effect of the triflate, nitrate, and Tf2N- anions on the hydrogen bond dynamics in the Ln3+ first solvation shell, with the effect being stronger in the Dy3+ solutions, due to the higher charge density of the Dy3+ ion as compared to La3+.

Redox Potentials for Tetraplatin, Satraplatin, Its Derivatives, and Ascorbic Acid: A Computational Study.

Redox potentials of the Pt(IV) complexes, such as satraplatin, tetraplatin, and several others, are determined at the density functional theory (DFT) level (with B3LYP, ω-B97XD, PBE1PBE, TPSSTPSS, M06-L, M11-L, and MN12-L functionals) and compared with post-Hartree-Fock methods MP2 and CCSD(T). Calculations are performed in water solution employing an implicit solvation model. The impact of replacement of a chloro ligand by a water molecule (hydration in the equatorial plane of the complexes) is also explored. Furthermore, an influence of solvent pH on the magnitude of the redox potentials is discussed for such hydrated complexes. The obtained results are compared with available experimental data leading to a root-mean-square deviation (RMSD) of ca. 0.23 V, using the CCSD(T)/6-31+G(d)/IEF-PCM/scaled-UAKS level. Distribution of the electron density is analyzed at the B3LYP/6-311++G(2df,2pd) level. Also, a correlation between binding energies of axial ligands and the redox potential is demonstrated. Since the Pt(IV) complexes are considered in the framework of anticancer treatment, possible reducing agents in bioenvironment are searched. From this reason, the reduction potential of different protonation states of ascorbic acid is also presented.

Preparation of near‐infrared Ag 2 S quantum dots for detection of bisphenol A in water

The work develops a novel method for the detection of bisphenol A (BPA) based on glutathione (GSH)-protected silver sulphide quantum dots (Ag2S QDs), which was simple, fast, non-toxic, sensitive and selective. Ag2S QDs were synthesised with a sulphur–hydrazine hydrate complex as the S2− source and GSH as the stabiliser. Ag2S QDs, near-infrared QDs, offered the advantages over lower background fluorescence and lower signal loss. The fluorescence peak of Ag2S QDs at 650 nm was quenched significantly in the presence of BPA. Good linear correlations were obtained over the concentration range from 0 to 60 μM of BPA under optimised conditions. The developed selective and sensitive method presaged more opportunities for the application in environmental samples.

Theoretical Models for Quantitative Description of the Acid-Base Equilibria of the 5,6-Substituted Uracils.

The acidities of 18 5,6-substituted uracils have been numerically estimated as pKa values in terms of three theoretical models. The first scheme includes the calculation of the gas-phase acidity of uracil with the G3MP2B3 method and taking into account the solvent effect using the polarizable continuum approximation PCM(SMD)-TPSS/aug-cc-pVTZ. The second model is one step and implies calculation of the free Gibbs energies of the hydrate complex of uracil (and its anion) with 5 water molecules by the TPSS/aug-cc-pVTZ method. This model accounts for the solvent effect corresponding to both specific and nonspecific solvation. The third scheme required high time and computational resources and includes the strong features of the two previous schemes. Here, the theoretical estimation of pKa is performed by the CBS-QB3 composite method. As in the second approach, both specific (as pentahydrate) and nonspecific solvent effects are determined. We have analyzed the advantages and model restrictions of the considered schemes for the pKa calculations. All models have systematic errors, which have been corrected with the linear empirical regression relations. In the presented model, the absolute mean deviations of the pKa values of uracils dissociating via the N1-H bonds diminish to 0.25, 0.28, and 0.23 pKa units (respectively, for I, II, and III models), which corresponds to ∼0.3 kcal/mol on the energy scale. The applicability of our computational schemes to uracils dissociating via N3-H, O-H (orotic acids) and C-H bonds is discussed.

Changing π-Interactions and Conformational Adjustments of N-(Isonicotinylhydrazide)-1,8-naphthalimide by Hydration and Complexation Affect Photophysical Properties

Noncovalent self-assemblies of different forms of a 1,8-naphthalimide derivative N-(isonicotinylhydrazide)-1,8-naphthalimide adopt different conformational adjustments due to the interplay of weak interactions. In such assemblies stacking interactions significantly contribute to direct the orientations of tether, which also influenced packing patterns. Effects of weak noncovalent interactions are reflected in the physicochemical properties of solvate and metal complexes of this naphthalimide derivative. Dual fluorescence emissions were observed from hydrate and silver complex of N-(isonicotinylhydrazide)-1,8-naphthalimide, which was not observed in anhydrous form of the compound. These results are compared with fluorescence emission study performed with solution of N-(isonicotinylhydrazide)-1,8-naphthalimide. Aggregation induced fluorescence emission of a solution in DMSO was caused by adding water. This emission in solution occurred at a much different emission wavelength than the emission observed from ...

A series of energetic metal pentazolate hydrates.

Singly or doubly bonded polynitrogen compounds can decompose to dinitrogen (N2) with an extremely large energy release. This makes them attractive as potential explosives or propellants, but also challenging to produce in a stable form. Polynitrogen materials containing nitrogen as the only element exist in the form of high-pressure polymeric phases, but under ambient conditions even metastability is realized only in the presence of other elements that provide stabilization. An early example is the molecule phenylpentazole, with a five-membered all-nitrogen ring, which was first reported in the 1900s and characterized in the 1950s. Salts containing the azide anion (N3-) or pentazenium cation (N5+) are also known, with compounds containing the pentazole anion, cyclo-N5-, a more recent addition. Very recently, a bulk material containing this species was reported and then used to prepare the first example of a solid-state metal-N5 complex. Here we report the synthesis and characterization of five metal pentazolate hydrate complexes [Na(H2O)(N5)]·2H2O, [M(H2O)4(N5)2]·4H2O (M = Mn, Fe and Co) and [Mg(H2O)6(N5)2]·4H2O that, with the exception of the Co complex, exhibit good thermal stability with onset decomposition temperatures greater than 100 °C. For this series we find that the N5- ion can coordinate to the metal cation through either ionic or covalent interactions, and is stabilized through hydrogen-bonding interactions with water. Given their energetic properties and stability, pentazole-metal complexes might potentially serve as a new class of high-energy density materials or enable the development of such materials containing only nitrogen. We also anticipate that the adaptability of the N5- ion in terms of its bonding interactions will enable the exploration of inorganic nitrogen analogues of metallocenes and other unusual polynitrogen complexes.

Evidence of promising biological-pharmacological activities of the sertraline-based copper complex: (SerH2)2[CuCl4

In the current study the ability of copper complex to exert multiple biological activities is combined with the pharmacological action of sertraline (SerH2Cl, antidepressant drug). The hydrated and anhydrous forms of the tetrachlorocuprate(II) salts, namely (SerH2)2[CuCl4]·½H2O and (SerH2)2[CuCl4], were synthesized and characterized by physicochemical methods. The crystal structures were determined by X-ray diffraction methods. The hydrate complex crystallizes in the monoclinic P21 space group with a=8.0807(2) Å, b=36.2781(8) Å, c=12.6576(3) Å, β=95.665(2)°, and Z=4 molecules per unit cell and the un-hydrate in P21 with a=13.8727(6) Å, b=7.5090(3) Å, c=18.618(1) Å, β=104.563(6)°, and Z=2. It has been suggested that Cu(II) ions might be critical in the development of mood disorders, showed potent biocidal activity, and also acted as analgesic adjuvant. To improve sertraline efficiency, the antidepressant and analgesic activities of the complex have been assessed in rats denoting a marked synergistic effect. Antithyroid and antimicrobial activities were also evaluated. Because depressive disorders and hyperthyroidism diseases led to an oxidative stress state, antioxidant capability has also been tested. The complex behaved as a good superoxide radical scavenger (IC50=6.3×10−6M). The ability of the complex to act as bromoperoxidase mimic was assessed. A pseudo-first order constant of k=0.157±0.007min−1 has been determined. The complex evidences promising biological-pharmacological activities and the albumin binding studies showed a Kb of 2.90×103M−1 showing an improvement in the uptake of sertraline by albumin at 8h incubation (time required for effective interaction of sertraline with the protein).

Effects of hydrogen bonding between pyrrole-2-carboxaldehyde and nearest polar and nonpolar environment

The present paper represents dominant effects of hydrogen bonding on the existence of different molecular aggregates in one of the heterocyclic pyrrole system: pyrrole-2-carboxaldehyde (PCL). Theoretical and experimental Raman spectral evidence verifies the existence of different molecular aggregates like dimeric, monomeric, hydrated complex states in PCL. Atoms in molecules (AIMs) analysis and fluorescence decay profile provide a strong signature of intermolecular hydrogen bonding (IerHB) as the possible reason for the existence of cis form of dimeric (X) molecular aggregates. The high remnant polarization of 3.13μCcm−2 and smaller dielectric loss in solid form of PCL arise due to in X by ordering of dipoles as a result of IerHB. A remarkable high ferroelectric response in solid phase makes PCL a desirable candidate to be used as raw material for energy storage devices. For solution phase, in presence of external hydroxylic environment, PCL reacts with external water molecules through weak IerHB and creates different hydrated PCL/(H2O)n complexes by creating water bridge with number of water molecules from 1 to n. An increasing number of water molecules helps to form stronger hydrated complex by separation of charges by lowering the transferring energy barrier.

Development of Lennard-Jones and Buckingham Potentials for Lanthanoid Ions in Water.

New sets of Lennard-Jones and Buckingham potentials have been developed to be used in classical molecular dynamics simulations of Ln3+-containing systems for the whole lanthanoid series. The force-field parameters have been refined by directly comparing the hydration structure obtained from the simulations with the extended X-ray absorption fine structure (EXAFS) experimental data, in order to reproduce Ln3+-water EXAFS experimentally inferred mean distances. Analysis of the simulation results has shown that both Lennard-Jones and Buckingham potentials are able to properly describe the radial distribution of water molecules around the Ln3+ ions, the smooth decrease of the hydration number along the lanthanoid series, as well as the geometry of the first-shell hydration complex formed by Ln3+ ions in water. The newly optimized interaction potential parameters can be used in conjunction with force fields available in the literature to investigate the solvation properties of Ln3+ ions in different disordered systems.

Effect of high pressure and temperature on volumetric properties of {water (1) + ethylenediamine (2)} mixtures

For {water (1)+ethylenediamine (2)} binary mixture the densities at atmospheric pressure and compressions, k=ΔV/Vo, at pressures from 10 to 100MPa of have been measured over the whole concentration range and temperatures from 278.15 to 323.15K. The molar isothermal compressions and molar isobaric expansions, the thermal pressure coefficients and the internal pressure of water+ethylenediamine mixture have been calculated at all state parameters examined. It was shown that the values of molar isothermal compression and molar isobaric expansion of the mixtures rich in water varied insignificantly whereas the thermal pressure coefficients changed strongly within that concentration range. The magnitude of the extreme on the concentration dependence of the thermal pressure coefficient was unusually large that was probably connected with the influence of 2H2O-EDA hydrate complex.

Soling, Aerating and Phosphating for Soil Strengthening and Detoxication

The article presents 3 new methods of soil simultaneous strengthening and detoxicating. The methods are based on using hydrate complexes obtained by means of silica sol, foam concrete and phosphates. 3 technologies are suggested after silica sol, foam concrete and phosphates. The new technologies are named soling, aerating and phosphating. The level of soil strengthening is from 0,2MPa for aerating and soling and more than 3MPa for phosphating. The point of detoxication is to obtain heavy metal ion silicates and phosphates with very low solubility product. The level of detoxication is more than 1000 TC (tolerable concentration, mg/g).

Unveiling the Reactivity of a Synthetic Mimic of the Oxygen Evolving Complex.

We simulated for the first time the oxygen-oxygen bond formation in a synthetic calcium-tetra manganese complex recently developed by Zhang and co-workers. In spite of promising structural similarities to the native oxygen evolving complex (OEC) in Photosystem II, several uncertainties on the mimic stability in water and on its potential catalytic activity still persist. Here, we characterized at density functional theory level the electronic and structural features of the Sn states of the complex, along with the oxygen-oxygen bond formation reaction, proposing a reasonable model for the hydrate complex. As a main finding, both the synthetic compound and the natural OEC show very close energetic barriers for the oxo-oxyl coupling process, suggesting that key electronic features of the natural OEC reactivity are well reproduced. This result strongly encourages the use of this synthetic complex in combination with other molecular assemblies for the design of successful artificial leaves.

Sensitivity analysis of multiphase flow in annulus during drilling of marine natural gas hydrate reservoirs

During drilling of marine natural gas hydrate reservoirs, hydrate cuttings will return upwards along with the drilling mud. As the temperature rises and the pressure drops, hydrate cuttings will decompose at a certain position. At that point a complex multiphase flow will form in the annulus. Moreover, the characteristic parameters of multiphase flow will significantly change in the upward progress of the flow, which is different from that in conventional drilling. Aiming at those situations, a new mathematical method is proposed for sensitivity analysis of multiphase flow in the annulus during drilling of marine natural gas hydrate reservoirs. In this method, temperature and pressure models in the wellbore, a dynamic model of hydrate mass transfer decomposition and complex multiphase flow models are established considering the interactions in the annulus. Then, using a numerical simulation method, models are used to analyze the laws of variation of temperature, pressure, hydrate dynamic decomposition and complex multiphase flow characteristics in the annulus under different operating parameters. After the sensitivity analysis of multiphase flow in annulus during drilling of marine natural gas hydrate reservoirs, it is presented that increasing delivery rate and density of drilling mud, reducing inlet temperature and rate of penetration should be performed to ensure well control safety. The research findings provide important theoretical bases and technical guidance for complex multiphase flow and well control safety analysis during drilling of marine natural gas hydrate reservoirs.

Crystal structure of μ-4-oxidobenzoato-κ2O1:O4-bis-[bis-(1,10-phenanthroline-κ2N,N')copper(II)] bis-(4-hy-droxy-benzoate) 7.5-hydrate.

The title hydrated complex, [Cu2(C7H4O3)(C12H8N2)4](C7H5O3)2·7.5H2O, is composed of dinuclear CuII complex cations, noncoordinating 4-hy-droxy-benzoate anions and water mol-ecules of crystallization. In the dinuclear complex cation, the CuII ions are bridged by a 4-oxidobenzoate ligand and thus each metal ion is five-coordinated by two chelating 1,10-phenanthroline (phen) mol-ecules and one anionic O atom in a distorted trigonal-bipyramid geometry. In the crystal, aromatic π-π stacking occurs between phen rings of neighbouring dinuclear CuII complex cations, forming two-dimensional supra-molecular systems parallel to (100).

Structure and electric properties of sodium ion hydrate shell in nanopore with hydrophilic walls

The method of molecular–level computer simulation at the temperature of 298 K was used to study the fundamental regularities of formation of electric properties of the hydrate shell of the Na+ cation in a planar model nanopore with hydrophilic structureless walls in contact with water vapors. Electric polarizability changes nonmonotonously: as consistent with the changes in the molecular structure of the system. Hydration within the pore occurs in several stages, from formation of chain structures, microdrop compaction and ejection of the ion from its own hydrate shell to encapsulation and absorption of the ion by the solvent preceding formation of nanoelectrolyte. Despite the significant differences in the energy of retaining hydrate shells for Na+ and Cl─ ions, polarizabilities of the two systems are close and behave similarly under variation of conditions. Strong spatial anisotropy of the polarizability tensor of the ion–hydrate complex is due to the effect of the nanopore walls on multiparticle spatial correlations in the system.

Ion Environments in Mn(2+)-Doped Polyelectrolyte Complexes: Dilute Magnetic Saloplastics.

Amorphous hydrated complexes of the polyelectrolytes poly(styrene sulfonate) (PSS) and poly(diallyldimethylammonium) were doped with the spin-5/2 ion Mn(2+). X-band electron paramagnetic resonance (EPR) measurements of the Mn(2+) spins within these stoichiometric polyelectrolyte complexes (PECs) revealed an octahedral coordination environment, similar to that observed in aqueous solutions of Mn(2+). This octahedral symmetry of the [Mn(H2O)6](2+) complexes, observed in fully hydrated PECs, is somewhat distorted because of the wide range of ion pairs possible with the sulfonate group on PSS. As the Mn(2+) concentration was increased, the linewidths broadened, indicating the dominance of dipolar broadening over exchange narrowing in determining the linewidths; that is, any exchange narrowing was masked by the large dipolar broadening. The calculated linewidths were used to estimate the strengths of the dipolar interactions, and hence the distances between the Mn(2+) spins, on the basis of a simple model of regularly spaced spins. The distances calculated by this method were roughly comparable to the geometric average distances calculated on the basis of the Mn(2+) concentrations and densities of the doped PEC samples. From a comparison of their EPR spectra, the ion environments in the doped, fully hydrated PECs were found to be similar to those in hydrated classical ion exchange resins. EPR spectra before and after drying of the PECs indicate the replacement of octahedrally coordinated water by oxide anions from the polyanion chain and the corresponding loss of the symmetric environment of Mn(2+) ions.

Preparation, characterization, molecular docking and in vitro evaluation of two novel morin hydrate/CD inclusion complexes

Two novel water-soluble morin hydrate (MH) complexes, composed of a hydrophobic MH core and hydrophilic cyclodextrin shell, were prepared and systematically investigated in both aqueous solution and the solid state by means of UV–Vis spectroscopy, 1H NMR, 2D NMR (ROESY), SEM, FT-IR, DSC, TGA, and XRD analysis. The characterization information resulting from these investigations revealed that the MH/cyclodextrin inclusion complexes formed by the MH with CD in 1:1 stoichiometry, and demonstrated satisfactory water solubility. The MH/cyclodextrin complexes still maintained antibacterial activity in vitro test against Staphylococcus aureus bacteria.

Lutetium(iii) aqua ion: On the dynamical structure of the heaviest lanthanoid hydration complex.

The structure and dynamics of the lutetium(iii) ion in aqueous solution have been investigated by means of a polarizable force field molecular dynamics (MD). An 8-fold square antiprism (SAP) geometry has been found to be the dominant configuration of the lutetium(iii) aqua ion. Nevertheless, a low percentage of 9-fold complexes arranged in a tricapped trigonal prism (TTP) geometry has been also detected. Dynamic properties have been explored by carrying out six independent MD simulations for each of four different temperatures: 277 K, 298 K, 423 K, 632 K. The mean residence time of water molecules in the first hydration shell at room temperature has been found to increase as compared to the central elements of the lanthanoid series in agreement with previous experimental findings. Water exchange kinetic rate constants at each temperature and activation parameters of the process have been determined from the MD simulations. The obtained structural and dynamical results suggest that the water exchange process for the lutetium(iii) aqua ion proceeds with an associative mechanism, in which the SAP hydration complex undergoes temporary structural changes passing through a 9-fold TTP intermediate. Such results are consistent with the water exchange mechanism proposed for heavy lanthanoid atoms.

XANES Reveals the Flexible Nature of Hydrated Strontium in Aqueous Solution.

X-ray absorption near-edge structure (XANES) spectroscopy has been used to determine the structure of the hydrated strontium in aqueous solution. The XANES analysis has been carried out using solid [Sr(H2O)8](OH)2 as reference model. Classical and Car-Parrinello molecular dynamics (MD) simulations have been carried out and in the former case two different sets of Lennard-Jones parameters have been used for the Sr(2+) ion. The best performing theoretical approach has been chosen on the basis of the experimental results. XANES spectra have been calculated starting from MD trajectories, without carrying out any minimization of the structural parameters. This procedure allowed us to properly account for thermal and structural fluctuations occurring in the aqueous solution in the analysis of the experimental spectrum. A deconvolution procedure has been applied to the raw absorption data thus increasing the sensitivity of XANES spectroscopy. One of the classical MD simulations has been found to provide a XANES theoretical spectrum in better agreement with the experimental data. An 8-fold hydration complex with a Sr-O distance of 2.60 Å has been found to be compatible with the XANES data, in agreement with previous findings. However, the hydration shells of the strontium ions have been found to have a flexible nature with a fast ligand exchange rate between the first and second hydration shell occurring in the picosecond time scale.