scholarly journals Characterization of Copper(II) Interactions with Sinefungin, a Nucleoside Antibiotic: Combined Potentiometric, Spectroscopic and DFT Studies

2007 ◽  
Vol 2007 ◽  
pp. 1-12 ◽  
Author(s):  
Maria Jaworska ◽  
Piotr Lodowski ◽  
Ariel Mucha ◽  
Wojciech Szczepanik ◽  
Gianni Valensin ◽  
...  
Keyword(s):  
Coordination Mode ◽  
Water Molecules ◽  
Equatorial Position ◽  
Coordination Pattern ◽  
Theoretical Studies ◽  
Free System ◽  
Mononuclear Complexes ◽  
Potentiometric Data

Interactions between sinefungin and copper(II) ions were investigated. Stoichiometry and stability constants of the metal-free system and two mononuclear complexes present in solution were determined on the basis of potentiometric data analysis. The results were compared to the Cu(II)-ornithine system due to structural similarities between both molecules. Combined spectroscopic and theoretical studies allowed for determination of coordination pattern for the Cu(II)-sinefungin complexes. At acidic pH, copper is bound in “glycine-like” coordination mode, identical with that of ornithine. This involvesα-amino group and the carboxyl oxygen. At higher pH, a “bis-complex” is formed by two sinefungin molecules. The second ligand binds in equatorial position displacing two water molecules, what results in the stable {2N,2O} coordination. Both axial positions are supposed to be occupied by N1 nitrogen donors of adenine moiety, what is confirmed by DFT calculations. They interact indirectly with copper(II) through water molecules as the result of dominantsynconformation of purine.

scholarly journals Where are the Atoms in Quasicrystals? Experimental and Theoretical Studies of Ternary and Quaternary Approximants

2000 ◽  
Vol 643 ◽  
Author(s):  
Gordon J. Miller ◽  
Chi-Shen Lee ◽  
Wen-Jiuan Tsai
Keyword(s):  
Theoretical Model ◽  
Electron Concentration ◽  
Valence Electron ◽  
Valence Electron Concentration ◽  
Theoretical Studies ◽  
Distribution Of Elements ◽  
Experimental And Theoretical Studies ◽  
Li Content

AbstractProblems concerning complete structural characterization of quasicrystals involve locating the atomic positions as well as determining the distribution of elements at each site. Quasicrystalline approximants provide models for potential building units of quasicrystals, but a clear determination of the elementaldecorations in such approximants also remains incomplete. We report experimental and theoretical studies of new, quaternary Bergman phases in the Li-Mg-Zn-Al system and a new, quasicrystalline approximant Li10Mg6Zn31Al3 (A16M34-type). A theoretical model using averaged Mulliken populations provides a means to track the segregation of elements (and vacancies) onto different sites as a function of valence electron concentration. As the Li content decreases, vacancies begin to occur at a specific site in the Bergman structure. The new approximant demonstrates how truncated tetrahedra can play an important role in forming clusters with possible fivefold symmetry in quasicrystalline structures.

Synthesis and structural characterization of N,N′-diarylpiperazine N,N′-dioxide tetrahydrates (aryl = o-tolyl, p-tolyl, p-chlorophenyl)

1988 ◽  
Vol 66 (8) ◽  
pp. 1836-1847 ◽  
Author(s):  
Chun-Kiu Kwok ◽  
Thomas C. W. Mak
Keyword(s):  
Crystal Packing ◽  
Direct Method ◽  
Water Molecules ◽  
Compound I ◽  
Space Group ◽  
X Ray ◽  
A Site ◽  
Compound Ii

The synthesis and X-ray structure determination of N,N′-di(o-tolyl)piperazine N,N′-dioxide tetrahydrate, I, N,N′-di(p-tolyl)piperazine N,N′-dioxide tetrahydrate, II, and N,N′-di(p-chlorophenyl)piperazine N,N′-dioxide tetrahydrate, III, are described. Compound I crystallizes in space group [Formula: see text] with a = 7.778(1), b = 7.915(2), c = 8.919(2) Å, α = 106.25(2), β = 99.56(1), γ = 108.80(2)°, and Z = 1. Compound II crystallizes in space group [Formula: see text] with a = 6.558(1), b = 7.134(2), c = 11.610(3) Å; α = 73.23(2), β = 78.08(2), γ = 72.67(2)°, and Z = 1. Compound III crystallizes in space group P21/c with a = 9.159(3), b = 12.390(4), c = 8.339(4) Å, β = 97.38(3)°, and Z = 2. The structures of I–III were solved by the direct method and refined to R = 0.049 (1749 observed MoKα reflections), 0.055 (2651 observed reflections), and 0.035 (1827 observed reflections), respectively. In each case, the N,N′-dioxide molecule occupies a site of symmetry [Formula: see text]. The piperazine ring takes the chair form, with two N—O bonds oriented axially in a trans configuration. The structures are characterized by strong hydrogen bonding between the water molecules, as well as between the N-oxide groups and water molecules, giving rise to puckered layers composed of various combinations of edge-sharing four-membered, six-membered, ten-membered, and twelve-membered rings. The aryl rings, which protrude on both sides of each puckered layer, constitute hydrophobic regions separating the hydrophilic layers in the crystal packing.

Structural Systematics of Rare Earth Complexes. XII Solvated 1 : 1 Adducts of Some Lanthanoid(III) Carboxylates with 1,10-Phenanthroline and 2,2′:6′,2″-Terpyridine

1999 ◽  
Vol 52 (6) ◽  
pp. 481 ◽  
Author(s):  
Cameron J. Kepert ◽  
Lioubov I. Semenova ◽  
Lu Wei-Min ◽  
Brian W. Skelton ◽  
Allan H. White
Keyword(s):  
Rare Earth ◽  
Single Crystal ◽  
Structural Characterization ◽  
Structure Determination ◽  
Room Temperature ◽  
Water Molecules ◽  
X Ray ◽  
Structural Characterizations

A room-temperature single-crystal X-ray structure determination of the 1 : 1 adduct of 1,10-phenanthroline (`phen") with lutetium(III) acetate (as its dihydrate) is recorded. Crystals are triclinic, P 1, a 12·430(8), b 10·681(4), c 8·134(8) Å, α 74·76(6), β 84·81(7), γ 74·29(4)°, Z = 2 f.u.; conventional R on |F| was 0·031 for No 3939 independent ‘observed’ (I > 3σ(I)) diffractometer reflections. The complex [(N,N′-phen)(O,O′-ac)Lu(O-ac-O′)4Lu(O,O′-ac)(N,N′-phen)].2H2O is binuclear, the lutetium being eight-coordinated by bidentate phen and ac (acetate) ligands and four oxygen atoms from the bridging acetate ligands. Also recorded is the structural characterization of 1 : 1 Lu(ac)2Cl/tpy (tpy = 2,2′:6′,2″-terpyridine) as its pentahydrate; this complex is triclinic, P 1, a 12·410(3), b 11·559(4), c 9·976(4) Å, α 85·19(3), β 70·30(3), γ 65·70(2)°, Z = 2, R 0·049 for No 4717. The complex is shown to be [(tpy)(H2O)2Lu(O2CCH3)2]Cl.3H2O, with the lutetium nine-coordinated by tridentate tpy, a pair of bidentate acetates and two unidentate water molecules, with the chloride uncoordinated. Structural characterizations of a number of 1 : 1 adducts of variously solvated lanthanoid(III) trichloroacetates, Ln(tca)3, with tpy are also recorded. Yb(tca)3/tpy/MeOH (1 : 1 : 1) is triclinic, P 1, a 14·016(4), b 12·951(5), c 9·604(3) Å, α 73·89(3), β 76·56(3), γ 69·20(3)°, Z = 2 f.u., R 0·057 for No 4465. The complex is mononuclear, the eight-coordinate N3YbO5 array containing tridentate tpy, unidentate methanol, and two unidentate and one bidentate chelating anions. 1 : 1 : 1 Ln(tca)3/tpy/OH2 adducts for Ln = La(-)Nd are triclinic, P 1, a ≈ 13·4, b ≈ 12·47, c ≈ 11·5 Å, α ≈ 114·5, β ≈ 89·9, γ ≈ 115·6°, Z = 1 binuclear array, R 0·061, 0·071 for No 3240, 2394. The two Ln atoms are O,O′-bridged by a pair of anions, the N3LnO6 nine-coordinate lanthanoid environment being completed by a tridentate tpy, one water, one unidentate and one bidentate anion. A 1 : 1 : 1 Lu(tca)3/tpy/OH2 array, by contrast, is triclinic, P 1, a 16·569(8), b 14·815(5), c 14·375(6) Å, α 62·05(3), β 81·35(4), γ 77·97(3)°, Z = 4 ‘mononuclear’ f.u., R 0·067 for No 6710. The array, remarkably, contains species of both of the above types in a 1 : 2 binuclear-to-mononuclear ratio, but with water replacing methanol in the mononuclear array.

scholarly journals Formation and structural characterization of a potassium amidinoguanidinate

2018 ◽  
Vol 74 (12) ◽  
pp. 1795-1799
Author(s):  
Volker Lorenz ◽  
Phil Liebing ◽  
Liane Hilfert ◽  
Sabine Busse ◽  
Frank T. Edelmann
Keyword(s):  
Structural Characterization ◽  
Structure Determination ◽  
Title Compound ◽  
Coordination Mode ◽  
Chain Structure ◽  
Polymeric Chain ◽  
X Ray ◽  
Potassium Hydride

The first potassium amidinoguanidinate complex, catena-poly[[bis(μ-1-amidinato-N,N′,N′′,N′′′-tetraisopropylguanidinato-κ5 N 1:N 1,N 2:N 2,N 4)dipotassium]-μ-1,2-dimethoxyethane-κ2 O:O′], [K2(C14H32N4)2(C4H10O2)] n or [{ i PrN= CHN( i Pr)N(N i Pr)2K}2(μ-DME)] n where DME is 1,2-dimethoxyethane, has been synthesized and structurally characterized. The title compound was isolated in 76% yield from a reaction of N,N′-diisopropylcarbodiimide with potassium hydride in DME. The single-crystal X-ray structure determination of the title compound revealed a polymeric chain structure comprising cage-like dimeric units, with the amidinoguanidinate ligand displaying a mixed σ-/π-coordination mode.

Characterization of a Crystalline Residue From a Swimming Pool: Disodium Copper(II) Tetrakis(isocyanurate) Hexahydrate

1992 ◽  
Vol 45 (11) ◽  
pp. 1927 ◽  
Author(s):  
RD Hart ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Chemical Analysis ◽  
Structure Determination ◽  
Title Compound ◽  
Swimming Pool ◽  
Water Molecules ◽  
Formula Unit ◽  
Sodium Ions ◽  
X Ray

Coupled with chemical analysis, a single-crystal X-ray structure determination of lilac deposit from a swimming pool, shows the deposit to be the title compound Na2Cu(C3H2N3O3)4.6H2O. Crystals are triclinic, P1, a 10.459(1), b 10.434(3), c 6.762(4) � , α: 71.73(4), β 83.67(4), γ 62.82(2), Z 1 formula unit; 1265 'observed' diffractometer reflections were refined to R 0.052. The copper atoms are located on crystallographic inversion centres, four-coordinated by a pair of water molecules [Cu-O, 1.937(6) � ] and a pair of ligand nitrogen atoms [Cu-N, 1.941(9) � ]. Interactions from ligand oxygen atoms to sodium ions link the structure into a polymeric array.

Characterization of Impressed Current Technique to Model Corrosion of Reinforcement in Concrete

2020 ◽  
Vol 11 (1) ◽  
pp. 93-99
Author(s):  
Abu Zakir Morshed ◽  
Sheikh Shakib ◽  
Tanzim Jahin
Keyword(s):  
Immersion Time ◽  
Chloride Content ◽  
Engineering Science ◽  
Coastal Regions ◽  
Faraday’S Law ◽  
Current Technique ◽  
Corrosion Cell ◽  
Impressed Current

Corrosion of reinforcement is an important durability concern for the structures exposed to coastal regions. Since corrosion of reinforcement involves long periods of time, impressed current technique is usually used to accelerate the corrosion of reinforcement in laboratories. Characterization of impressed current technique was the main focus of this research,which involved determination of optimum chloride content and minimum immersion time of specimens for which the application of Faraday’s law could be efficient. To obtain optimum chloride content, the electrolytes in the corrosion cell were prepared similar to that of concrete pore solutions. Concrete prisms of 200 mm by 200 mm by 300 mm were used to determine the minimum immersion time for saturation. It was found that the optimum chloride content was 35 gm/L and the minimum immersion time for saturation was 140 hours. Accounting the results, a modified expression based on Faraday’s law was proposed to calculate weight loss due to corrosion. Journal of Engineering Science 11(1), 2020, 93-99

The Determination of Sense via Deleuze and Blanchot: Paradoxes of the Habitual, the Immemorial, and the Eternal Return

2008 ◽  
Vol 2 (2) ◽  
pp. 155-177 ◽  
Author(s):  
Eugene Brently Young
Keyword(s):  
Eternal Return

Eternal return is the paradox that accounts for the interplay between difference and repetition, a dynamic at the heart of Deleuze's philosophy, and Blanchot's approach to this paradox, even and especially through what it elides, further illuminates it. Deleuze draws on Blanchot's characterisations of difference, forgetting, and the unlivable to depict the ‘sense’ produced via eternal return, which, for Blanchot, is where repetition implicates or ‘carries’ pure difference. However, for Deleuze, difference and the unlivable are also developed by the living repetition or ‘contraction’ of habit, which results in his distinctive characterization of ‘force’, ‘levity’, and sense in eternal return.

SEM/EDS Characterization of Uncommon Metal Whiskers and Determination of Underlying Growth Mechanisms

2018 ◽  
Author(s):  
D. Basak ◽  
L. H. Ponce
Keyword(s):  
Reliability Analysis ◽  
Case Studies ◽  
Whisker Growth ◽  
Innovation Systems ◽  
Growth Mechanisms ◽  
Crystal Oscillator ◽  
Analysis Laboratory ◽  
Investigative Techniques

Abstract Two case-studies on uncommon metals whiskers, performed at the Reliability Analysis Laboratory (RAL) of Northrop Grumman Innovation Systems, are presented. The components analyzed are an Oven Controlled Crystal Oscillator (OCXO) and an Electromechanical Relay. Investigative techniques were used to determine the chemical and physical makeup of the metal whiskers and develop an understanding of the underlying effects and mechanisms that caused the conditions conducive to whisker growth.

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