Structure and electrochemical behaviour of 2-nitrosoquinoxaline

1981 ◽  
Vol 59 (12) ◽  
pp. 1711-1716 ◽  
Author(s):  
Joseph Armand ◽  
Yvette Armand ◽  
Line Boulares ◽  
Michèle Philoche-Levisalles ◽  
Jean Pinson
Keyword(s):  
Equilibrium Constant ◽  
Electrochemical Reduction ◽  
Acidic Medium ◽  
Electrochemical Behaviour ◽  
Monomeric Form ◽  
X Ray ◽  
X Ray Crystallography

It is shown by X-ray crystallography that 2-nitrosoquinoxaline crystallizes as a dimer, the structure of which is established. In solution the monomeric form predominates and the dimerisation equilibrium constant is measured. The electrochemical reduction of 2-nitrosoquinoxaline in acidic medium leads to the oxime of quinoxaline (1H)-2-one (3) through the intermediate hydroxylamine. 3 is electrochemically reoxidized directly to 2-nitrosoquinoxaline.

Synthesis and Electrochemical Studies of Nickel β-Diketonate Complexes Incorporating Asymmetric Diimine Ligands

2010 ◽  
Vol 63 (1) ◽  
pp. 75 ◽  
Author(s):  
Phimphaka Harding ◽  
David J. Harding ◽  
Nitisastr Soponrat ◽  
Kittiya Tinpun ◽  
Sirirat Samuadnuan ◽  
...  
Keyword(s):  
Electrochemical Behaviour ◽  
Nickel Complexes ◽  
Electrochemical Studies ◽  
Peak Potential ◽  
Aryl Ring ◽  
X Ray ◽  
Coordination Modes ◽  
X Ray Crystallography ◽  
Diimine Ligands

The reaction of ppaX {(4-X-phenyl)-pyridin-2-ylmethylene-amine; X = H, Me, Et, OMe, F, Cl, Br, and I} with [Ni(β-diketonate)2(H2O)2] {β-diketonate = 1,3-diphenylpropanedionate (dbm), 2,2,6,6-tetramethyl-3,5-heptadionate (tmhd), or hexafluoroacetylacetonate (hfac)} yields a series of nickel complexes. X-ray crystallography reveals octahedral coordinated nickel centres with a cis arrangement of the β-diketonate ligands. The β-diketonate ligands adopt ‘planar’ or ‘bent’ coordination modes, whereas the aryl ring of the ppaX ligand is twisted with respect to the pyridylimine unit. The electrochemical behaviour of the complexes reveals quasi-reversible or irreversible one-electron oxidation to Ni(iii) in the case of the [Ni(tmhd)2(ppaX)] and [Ni(dbm)2(ppaX)] complexes, respectively. The peak potential for oxidation is dependent on the type of β-diketonate ligand but essentially independent of the substituent, X, on the ppaX ligand. The [Ni(β-diketonate)2(ppaX)] complexes (X = F, Cl, Br, and I) also undergo ligand based reduction.

Water-soluble Bis(thiosemicarbazonato)copper(II) Complexes

2011 ◽  
Vol 64 (3) ◽  
pp. 244 ◽  
Author(s):  
Gojko Buncic ◽  
James L. Hickey ◽  
Christine Schieber ◽  
Jonathan M. White ◽  
Peter J. Crouch ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Cyclic Voltammetry ◽  
Nmr Spectroscopy ◽  
Cellular Uptake ◽  
Copper Complexes ◽  
Electrochemical Behaviour ◽  
Water Soluble ◽  
X Ray ◽  
X Ray Crystallography ◽  
Reversible Redox

The synthesis of four new water-soluble bis(thiosemicarbazone) ligands and their copper(ii) complexes is presented and their potential to be new ligands for copper radiopharmaceuticals is discussed. The ligands and complexes have been characterized by a combination of NMR spectroscopy, mass spectrometry, and X-ray crystallography. The electrochemical behaviour of two of the copper(ii) complexes was investigated by cyclic voltammetry and revealed that both complexes exhibited a quasi-reversible redox process attributed to a CuII/CuI process. Two of the new ligands were radiolabelled with positron-emitting 64Cu with a view to assessing their potential as ligands that bind radioactive copper isotopes for application in diagnostic radiopharmaceuticals. The cellular uptake of the copper complexes was investigated in SH-SY5Y cells.

scholarly journals Glycerol and Q-Tubes: Green Catalyst and Technique for Synthesis of Polyfunctionally Substituted Heteroaromatics and Anilines

Molecules ◽  
2019 ◽  
Vol 24 (9) ◽  
pp. 1806 ◽  
Author(s):  
Douaa Salman AlMarzouq ◽  
Noha M. Hilmy Elnagdi
Keyword(s):  
Acidic Medium ◽  
Catalytic Effect ◽  
Spectroscopic Methods ◽  
Green Solvent ◽  
Substituted Anilines ◽  
Green Catalyst ◽  
X Ray ◽  
X Ray Crystallography ◽  
Water Glycerol

The role of glycerol as a green bio-based solvent, reactant, and/or a catalyst in the synthesis of novel heterocycles, under pressure, is studied. Synthesis of novel quinolines in good yields using a new modified Skraup synthesis, utilizing glycerol and pressure Q-tubes, is demonstrated. Novel aniline trimers are prepared using glycerol, and substituted anilines under pressure, in acidic medium and water. Glycerol was employed as a catalyst and a green solvent in the synthesis of novel pyridazines 13a–c. The mechanisms of the reactions and the catalytic effect of glycerol in protic and aprotic media are fully discussed. The structures of the synthesized compounds were determined via X-ray crystallography and spectroscopic methods.

Monomeric Form of Peptidylarginine Deiminase Type I Revealed by X-ray Crystallography and Small-Angle X-ray Scattering

2016 ◽  
Vol 428 (15) ◽  
pp. 3058-3073 ◽  
Author(s):  
Shinya Saijo ◽  
Anna Nagai ◽  
Saya Kinjo ◽  
Ryutaro Mashimo ◽  
Megumi Akimoto ◽  
...  
Keyword(s):  
Small Angle ◽  
Type I ◽  
Monomeric Form ◽  
Peptidylarginine Deiminase ◽  
X Ray ◽  
X Ray Crystallography ◽  
X Ray Scattering ◽  
Ray Scattering

Pseudo-oxocarbons complexes - complexation of 2,4-bis(dicyanomethylene)-cyclobutane-1,3-dione dianion with copper. X-ray identification and electrochemical properties of the dianion and copper(I) and (II) complexes

2000 ◽  
Vol 78 (2) ◽  
pp. 280-290 ◽  
Author(s):  
Paul-Louis Fabre ◽  
Christophe Pena ◽  
Anne Marie Galibert ◽  
Brigitte Soula ◽  
Gérald Bernardinelli ◽  
...  
Keyword(s):  
Copper Complexes ◽  
Electrochemical Behaviour ◽  
Monoclinic Space Group ◽  
Crystal Data ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
X Ray Crystallography ◽  
Polymeric Chains ◽  
Complex Copper

The compound (Ph4P)2(trans-cdcb)·2H2O (trans-cdcb2- = 2,4-bis(dicyanomethylene)-cyclobutane-1,3-dione dianion) has been synthesized and characterized by X-ray crystallography. Crystal data: triclinic, space group P1, a = 10.829(2) Å, b = 11.297(2) Å, c = 11.515(2) Å, α = 79.61(1)°, β = 68.54(1)°, γ = 63.49(1)°, V = 1172.9(4) Å3, Z = 1, R = 0.036, Rw = 0.047. With the dianion as a ligand, two complexes have been obtained and characterized by X-ray crystallography, UV-visible spectroscopy, and electrochemistry. The copper(II) complex [Cu(trans-cdcb)(H2O)4·2H2O]n consists of polymeric chains with copper atoms bonded to two of the nitrile groups of the ligand. Crystal data: monoclinic, space group P21/c, a = 9.6366(6) Å, b = 7.1292(3) Å, c = 10.7018(6) Å, β = 99.603(4)°, V = 724.92(7) Å3, Z = 2, R = 0.026, Rw = 0.041. The copper(I) complex[Cu2(trans-cdcb)(CH3CN)4·2CH3CN]n consists of polymeric chains with copper atoms bonded by all the four nitrile groups of the ligand. Crystal data: monoclinic, space group P21/n, a = 10.654(2) Å, b = 8.736(1) Å, c = 14.654(3) Å, β = 109.01(2)°, V = 1291.3(9) Å3, Z = 2, R = 0.037, Rw = 0.041. In CH3CN solution, the copper complexes are dissociated. Moreover, copper(II) is reduced into copper(I) by the dianion. Electrochemistry in the solid state (polymer coated electrode) showed the redox transitions of the different compounds.Key words: pseudo-oxocarbons, X-ray diffraction, copper(II) complex, copper(I) complex, electrochemical behaviour.

Difference Fourier Analysis of Glucose Embedded and Frozen Hydrated Purple Membrane

1982 ◽  
Vol 40 ◽  
pp. 74-75
Author(s):  
Jules S. Jaffe ◽  
Robert M. Glaeser
Keyword(s):  
Purple Membrane ◽  
Data Set ◽  
High Resolution Data ◽  
X Ray ◽  
X Ray Crystallography ◽  
Fourier Techniques ◽  
Versus Protein ◽  
The Difference ◽  
Difference Fourier ◽  
Ideal Method

Although difference Fourier techniques are standard in X-ray crystallography it has only been very recently that electron crystallographers have been able to take advantage of this method. We have combined a high resolution data set for frozen glucose embedded Purple Membrane (PM) with a data set collected from PM prepared in the frozen hydrated state in order to visualize any differences in structure due to the different methods of preparation. The increased contrast between protein-ice versus protein-glucose may prove to be an advantage of the frozen hydrated technique for visualizing those parts of bacteriorhodopsin that are embedded in glucose. In addition, surface groups of the protein may be disordered in glucose and ordered in the frozen state. The sensitivity of the difference Fourier technique to small changes in structure provides an ideal method for testing this hypothesis.

3-D reconstruction of molecular shape from microcrystal thin sections

1983 ◽  
Vol 41 ◽  
pp. 748-749
Author(s):  
S. Cusack ◽  
J.-C. Jésior
Keyword(s):  
Three Dimensional ◽  
Molecular Shape ◽  
Biological Molecules ◽  
Fourier Space ◽  
Single Particles ◽  
Thin Sections ◽  
Standard Methods ◽  
X Ray ◽  
X Ray Crystallography ◽  
Dimensional Reconstruction

Three-dimensional reconstruction techniques using electron microscopy have been principally developed for application to 2-D arrays (i.e. monolayers) of biological molecules and symmetrical single particles (e.g. helical viruses). However many biological molecules that crystallise form multilayered microcrystals which are unsuitable for study by either the standard methods of 3-D reconstruction or, because of their size, by X-ray crystallography. The grid sectioning technique enables a number of different projections of such microcrystals to be obtained in well defined directions (e.g. parallel to crystal axes) and poses the problem of how best these projections can be used to reconstruct the packing and shape of the molecules forming the microcrystal.Given sufficient projections there may be enough information to do a crystallographic reconstruction in Fourier space. We however have considered the situation where only a limited number of projections are available, as for example in the case of catalase platelets where three orthogonal and two diagonal projections have been obtained (Fig. 1).

Electron microscopy of rabbit FC crystals

1983 ◽  
Vol 41 ◽  
pp. 730-731
Author(s):  
Robert A. Grant ◽  
Laura L. Degn ◽  
Wah Chiu ◽  
John Robinson
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Molecular Replacement ◽  
X Ray ◽  
X Ray Crystallography ◽  
Resolution Electron ◽  
Replacement Technique ◽  
Hydrated Crystal ◽  
Molecular Structure Analysis

Proteolytic digestion of the immunoglobulin IgG with papain cleaves the molecule into an antigen binding fragment, Fab, and a compliment binding fragment, Fc. Structures of intact immunoglobulin, Fab and Fc from various sources have been solved by X-ray crystallography. Rabbit Fc can be crystallized as thin platelets suitable for high resolution electron microscopy. The structure of rabbit Fc can be expected to be similar to the known structure of human Fc, making it an ideal specimen for comparing the X-ray and electron crystallographic techniques and for the application of the molecular replacement technique to electron crystallography. Thin protein crystals embedded in ice diffract to high resolution. A low resolution image of a frozen, hydrated crystal can be expected to have a better contrast than a glucose embedded crystal due to the larger density difference between protein and ice compared to protein and glucose. For these reasons we are using an ice embedding technique to prepare the rabbit Fc crystals for molecular structure analysis by electron microscopy.

In Situ X-Ray Absorption Studies of the Electrochemical Reduction of Hydroxocobalamin

1997 ◽  
Vol 7 (C2) ◽  
pp. C2-619-C2-620 ◽  
Author(s):  
M. Giorgett ◽  
I. Ascone ◽  
M. Berrettoni ◽  
S. Zamponi ◽  
R. Marassi
Keyword(s):  
Electrochemical Reduction ◽  
X Ray ◽  
Absorption Studies ◽  
X Ray Absorption
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