The polarography of beryllium

1964 ◽  
Vol 17 (10) ◽  
pp. 1072 ◽  
Author(s):  
PJ Shirvington ◽  
TM Florence ◽  
AJ Harle
Keyword(s):  
Aqueous Media ◽  
Electrode Reaction ◽  
Complexing Agents ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Reduction Step ◽  
Current Time ◽  
Diffusion Controlled ◽  
Coordinated Water ◽  
Potentiometric Data

The polarography of beryllium in 0.5M lithium chloride has been investigated in some detail, using several polarographic and coulometric techniques. Current-time curves, microscopic examination and cinematography of the mercury drop, and the effect of complexing agents, aided in elucidating the electrode process. The experimental data show that the polarographic step for the tetraquoberyllium ion is diffusion-controlled but irreversible, and results from the reduction of two protons liberated from the coordinated water molecules, yielding beryllium hydroxide and hydrogen. The evidence suggests that this reduction takes place in a stepwise process, with a soluble beryllium hydroxy complex as an intermediate. The polarographic results can be correlated with published potentiometric data on the composition and stabilities of hydrolysed beryllium species in aqueous media. The number of electrons involved in the electrode reaction depends on the number of hydroxyl groups per beryllium atom in the beryllium complex. Beryllium oxalate and salicylate complexes also give a reduction step, but only if the complex contains coordinated water molecules. The diffusion coefficient of the tetraquoberyllium ion was found to be 6.2 � 0.3 x 10-6 cm2 sec-1 at 30�.

Polarography of azobenzene and its p-sulphonic acids

1964 ◽  
Vol 17 (10) ◽  
pp. 1085 ◽  
Author(s):  
TM Florence ◽  
YJ Farrar
Keyword(s):  
Ph Effect ◽  
Aqueous Media ◽  
Mercury Electrode ◽  
Electrode Reaction ◽  
Ammonium Ions ◽  
Current Time ◽  
Electrode Processes ◽  
Ph Values ◽  
Strong Adsorption ◽  
Dropping Mercury Electrode

The behaviour at the dropping mercury electrode of trans-azobenzene and its p-sulphonic acids has been studied by several techniques including d.c., a.c., single sweep, and Kalousek polarography. Current-potential curves recorded at the streaming mercury electrode provided information on the reversibility of the electrode processes, while current-time and electrocapillary curves aided in elucidating the effects of adsorption. The results show that the rate of the electrode reaction of the azo-hydrazo couple is dependent on pH, the minimum rate occurring near pH 9 for azobenzene-4-sulphonic acid in aqueous media. At very low and high pH values, the couple approaches full reversibility at the dropping mercury electrode. This pH effect is apparently due to strong adsorption of both the azo and hydrazo derivatives near the potential of the electrocapillary maximum. Ammonium ions associate with azobenzene-4-sulphonate, and improve the reversibility in intermediate pH regions.

QM/MM Simulations of Organic Phosphorus Adsorption at the Diaspore-Water Interface

2019 ◽  
Author(s):  
Prasanth Babu Ganta ◽  
Oliver Kühn ◽  
Ashour Ahmed
Keyword(s):  
Interaction Energy ◽  
Dynamics Simulation ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Water Interface ◽  
Mineral Surfaces ◽  
Soil Mineral ◽  
Phosphorus Adsorption ◽  
Covalent Bonds ◽  
Binding Mechanisms

The phosphorus (P) immobilization and thus its availability for plants are mainly affected by the strong interaction of phosphates with soil components especially soil mineral surfaces. Related reactions have been studied extensively via sorption experiments especially by carrying out adsorption of ortho-phosphate onto Fe-oxide surfaces. But a molecular-level understanding for the P-binding mechanisms at the mineral-water interface is still lacking, especially for forest eco-systems. Therefore, the current contribution provides an investigation of the molecular binding mechanisms for two abundant phosphates in forest soils, inositol hexaphosphate (IHP) and glycerolphosphate (GP), at the diaspore mineral surface. Here a hybrid electrostatic embedding quantum mechanics/molecular mechanics (QM/MM) based molecular dynamics simulation has been applied to explore the diaspore-IHP/GP-water interactions. The results provide evidence for the formation of different P-diaspore binding motifs involving monodentate (M) and bidentate (B) for GP and two (2M) as well as three (3M) monodentate for IHP. The interaction energy results indicated the abundance of the GP B motif compared to the M one. The IHP 3M motif has a higher total interaction energy compared to its 2M motif, but exhibits a lower interaction energy per bond. Compared to GP, IHP exhibited stronger interaction with the surface as well as with water. Water was found to play an important role in controlling these diaspore-IHP/GP-water interactions. The interfacial water molecules form moderately strong H-bonds (HBs) with GP and IHP as well as with the diaspore surface. For all the diaspore-IHP/GP-water complexes, the interaction of water with diaspore exceeds that with the studied phosphates. Furthermore, some water molecules form covalent bonds with diaspore Al atoms while others dissociate at the surface to protons and hydroxyl groups leading to proton transfer processes. Finally, the current results confirm previous experimental conclusions indicating the importance of the number of phosphate groups, HBs, and proton transfers in controlling the P-binding at soil mineral surfaces.

A gadolinium cryptate with two coordinated water molecules

1998 ◽  
pp. 3711-3714 ◽  
Author(s):  
S. W. Annie Bligh ◽  
Michael G. B. Drew ◽  
Noreen Martin ◽  
Beatrice Maubert ◽  
Jane Nelson
Keyword(s):  
Water Molecules ◽  
Coordinated Water

scholarly journals Entropy-driven binding of gut bacterial β-glucuronidase inhibitors ameliorates irinotecan-induced toxicity

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Hsien-Ya Lin ◽  
Chia-Yu Chen ◽  
Ting-Chien Lin ◽  
Lun-Fu Yeh ◽  
Wei-Che Hsieh ◽  
...  
Keyword(s):  
Cancer Metabolism ◽  
Glucuronic Acid ◽  
Intestinal Epithelial Cells ◽  
Primary Treatment ◽  
Water Molecules ◽  
Intestinal Epithelial ◽  
E Coli ◽  
Severe Diarrhea ◽  
Coordinated Water ◽  
Consequent Increase

AbstractIrinotecan inhibits cell proliferation and thus is used for the primary treatment of colorectal cancer. Metabolism of irinotecan involves incorporation of β-glucuronic acid to facilitate excretion. During transit of the glucuronidated product through the gastrointestinal tract, an induced upregulation of gut microbial β-glucuronidase (GUS) activity may cause severe diarrhea and thus force many patients to stop treatment. We herein report the development of uronic isofagomine (UIFG) derivatives that act as general, potent inhibitors of bacterial GUSs, especially those of Escherichia coli and Clostridium perfringens. The best inhibitor, C6-nonyl UIFG, is 23,300-fold more selective for E. coli GUS than for human GUS (Ki = 0.0045 and 105 μM, respectively). Structural evidence indicated that the loss of coordinated water molecules, with the consequent increase in entropy, contributes to the high affinity and selectivity for bacterial GUSs. The inhibitors also effectively reduced irinotecan-induced diarrhea in mice without damaging intestinal epithelial cells.

Synthesis and Characterization of Lanthanide Metal-Organic Frameworks with Perfluorinated Linkers

2016 ◽  
Vol 98 ◽  
pp. 70-74
Author(s):  
Andrius Laurikėnas ◽  
Jurgis Barkauskas ◽  
Aivaras Kareiva
Keyword(s):  
Metal Organic Frameworks ◽  
Aqueous Media ◽  
Xrd Analysis ◽  
X Ray Diffraction ◽  
Lanthanide Elements ◽  
Diffusion Controlled ◽  
Benzenedicarboxylic Acid ◽  
Metal Organic ◽  
Lanthanide Metal

In this study, lanthanide elements (Ln3+) and 2,3,5,6-tetrafluoro-1,4-benzenedicarboxylic acid (TFBDC) based metal-organic frameworks (MOFs) were synthesized by precipitation and diffusion-controlled precipitation methods. Powders insoluble in aqueous media and polar solvents were obtained. The microstructure and properties of Ln3+ MOFs were evaluated and discussed. X-ray diffraction (XRD) analysis, infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and fluorescence spectroscopy (FLS) were carried out to characterize Ln3+ MOF's crystallinity, the microstructure, chemical composition and optical properties.

scholarly journals Crystal structure of poly[diaquabis(μ5-benzene-1,3-dicarboxylato)(N,N-dimethylformamide)cadmium(II)disodium(I)]

2017 ◽  
Vol 73 (11) ◽  
pp. 1599-1602 ◽  
Author(s):  
Matimon Sangsawang ◽  
Kittipong Chainok ◽  
Nanthawat Wannarit
Keyword(s):  
Crystal Structure ◽  
Coordination Polymer ◽  
Hydrogen Bonds ◽  
Three Dimensional ◽  
Water Molecules ◽  
Asymmetric Unit ◽  
Carboxylate Groups ◽  
Benzene Rings ◽  
Coordinated Water ◽  
Coordinate Geometry

The title compound, [CdNa2(C8H4O4)2(C3H7NO)(H2O)2]nor [CdNa2(1,3-bdc)2(DMF)(H2O)2]n, is a new CdII–NaIheterobimetallic coordination polymer. The asymmetric unit consists of one CdIIatom, two NaIatoms, two 1,3-bdc ligands, two coordinated water molecules and one coordinated DMF molecule. The CdIIatom exhibits a seven-coordinate geometry, while the NaIatoms can be considered to be pentacoordinate. The metal ions and their symmetry-related equivalents are connectedviachelating–bridging carboxylate groups of the 1,3-bdc ligands to generate a three-dimensional framework. In the crystal, there are classical O—H...O hydrogen bonds involving the coordinated water molecules and the 1,3-bdc carboxylate groups and π–π stacking between the benzene rings of the 1,3-bdc ligands present within the frameworks.

scholarly journals Crystal structure ofcatena-poly[[[tetraaquairon(II)]-trans-μ-1,2-bis(pyridin-4-yl)ethene-κ2N:N′] bis(p-toluenesulfonate) methanol disolvate]

2017 ◽  
Vol 73 (12) ◽  
pp. 1977-1980
Author(s):  
Volodymyr M. Hiiuk ◽  
Diana D. Barakhty ◽  
Sergiu Shova ◽  
Ruslan A. Polunin ◽  
Il'ya A. Gural'skiy
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Three Dimensional ◽  
Distorted Octahedral Geometry ◽  
Water Molecules ◽  
Supramolecular Network ◽  
Polymeric Complex ◽  
Distorted Octahedral ◽  
Polymeric Chains ◽  
Coordinated Water

In the title polymeric complex, {[Fe(C12H10N2)2(H2O)4](CH3C6H4SO3)2·2CH3OH}n, the FeIIcation, located on an inversion centre, is coordinated by four water molecules in the equatorial positions and two 1,2-bis(pyridin-4-yl)ethene molecules in the axial positions. This results in a distorted octahedral geometry for the [N2O4] coordination polyhedron. The 1,2-bis(pyridin-4-yl)ethene molecules bridge the FeIIcations, forming polymeric chains running along thea-axis direction. Stabilization of the crystal structure is provided by O—H...O hydrogen bonds; these are formed by coordinated water molecules as donors towards the O atoms of the methanol molecules and tosylate anions as acceptors of protons, leading to the formation of a three-dimensional supramolecular network. Weak C—H...O hydrogen bonds are also observed in the crystal.

scholarly journals Crystal structure of a nickel compound comprising two nickel(II) complexes with different ligand environments: [Ni(tren)(H2O)2][Ni(H2O)6](SO4)2

2020 ◽  
Vol 76 (3) ◽  
pp. 314-317
Author(s):  
Karilys González Nieves ◽  
Dalice M. Piñero Cruz
Keyword(s):  
Crystal Structure ◽  
Title Compound ◽  
Molar Ratio ◽  
Water Molecules ◽  
Nickel Compound ◽  
Counter Anion ◽  
Cationic Complex ◽  
Coordinated Water ◽  
Co Precipitation ◽  
Metal Ligand

The title compound, diaqua[tris(2-aminoethyl)amine]nickel(II) hexaaquanickel(II) bis(sulfate), [Ni(C6H18N4)(H2O)2][Ni(H2O)6](SO4)2 or [Ni(tren)(H2O)2][Ni(H2O)6](SO4)2, consists of two octahedral nickel complexes within the same unit cell. These metal complexes are formed from the reaction of [Ni(H2O)6](SO4) and the ligand tris(2-aminoethyl)amine (tren). The crystals of the title compound are purple, different from those of the starting complex [Ni(H2O)6](SO4), which are turquoise. The reaction was performed both in a 1:1 and 1:2 metal–ligand molar ratio, always yielding the co-precipitation of the two types of crystals. The asymmetric unit of the title compound, which crystallizes in the space group Pnma, consists of two half NiII complexes and a sulfate counter-anion. The mononuclear cationic complex [Ni(tren)(H2O)2]2+ comprises an Ni ion, the tren ligand and two water molecules, while the mononuclear complex [Ni(H2O)6]2+ consists of another Ni ion surrounded by six coordinated water molecules. The [Ni(tren)(H2O)2] and [Ni(H2O)6] subunits are connected to the SO4 2− counter-anions through hydrogen bonding, thus consolidating the crystal structure.

scholarly journals Synthesis, Single Crystal Structural Investigation, Hirshfeld Surface Analysis, Thermoanalysis and Spectroscopic Study of Two New Cu(II) and Co(II) Transition-Metal Complexes

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 986
Author(s):  
Rim Boubakri ◽  
Mirosław Szybowicz ◽  
Mariola Sadej ◽  
Sarra Soudani ◽  
Frédéric Lefebvre ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Single Crystal ◽  
Organic Ligand ◽  
Free Water ◽  
Pyrimidine Ring ◽  
Water Molecules ◽  
Absorption Bands ◽  
Infrared And Raman Spectroscopy ◽  
Homo And Lumo ◽  
Coordinated Water

Two new complexes, [Cu(dimpyr)2(H2O)2](NO3)2.2H2O (1) and (Hamdimpy)2[CoCl4].H2O (2), with the monodentate ligand 2-amino-6-methylpyrimidin-4-(1H)-one (dimpyr) and the countercation 4-amino-2,6-dimetylpyrimidium (Hamdimpy), respectively, were prepared and characterized by single crystal X-ray diffraction, elemental analysis and IR spectroscopy. In (1), the Cu(II) cation is tetracoordinated, in a square plan fashion, by two nitrogen atoms from the pyrimidine ring of the organic ligand and two oxygen atoms of two coordinated water molecules. In the atomic arrangement, the CuO2N2 square planes are interconnected via the formation of O-H…O hydrogen bonds involving both coordinated and free water molecules and NO3− nitrate anions to form inorganic layers parallel to the (a, b) plane at z = (2n + 1)/4. In (2), the central atom Co(II) is four-coordinated in a distorted tetrahedral fashion by four Cl− ions. The [CoCl4]2− tetrahedra are arranged parallel to the plane (110) at x = (2n + 1)/2 and the organic cations are grafted between them by establishing with them hydrogen bonds of CH…Cl and NH…Cl types. The vibrational absorption bands were identified by infrared and Raman spectroscopy. Intermolecular interactions were investigated via Hirshfeld surfaces and electronic properties such as HOMO and LUMO energies were derived. The two compounds were characterized by thermal analysis to determine their thermal behavior with respect to temperature.

The behaviour of copper(II) dithiocarbamates at the mercury electrode

1976 ◽  
Vol 29 (1) ◽  
pp. 85 ◽  
Author(s):  
TH Randle ◽  
TJ Cardwell ◽  
RJ Magee
Keyword(s):  
Propylene Carbonate ◽  
Electrochemical Techniques ◽  
Mercury Electrode ◽  
Alkyl Substituent ◽  
Reduction Step ◽  
Electron Diffusion ◽  
Reduction Potentials ◽  
Diffusion Controlled

The reduction at the mercury electrode of a series of copper(11) dithiocarbamates [CU(S2CNR2)2] in propylene carbonate has been investigated by a variety of electrochemical techniques. Thecomplexes undergo reduction in two successive one-electron diffusion-controlled steps, with associated adsorption of the complexes and the reduction products. Exhaustive reduction at a mercury-pool electrode shows the completely reduced species [CU(S2CNR2)2]2- to undergo slowdissociation. The alkyl substituent influences the strength of adsorption of the reduction products, the reduction potentials of the complexes and the reversibility of the first reduction step, thesecond step being quasi-reversible in all cases. The electroactive centre appears to be the metal.

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