Patrick Sharrock

Spectroscopic, magnetic and structural characterization of tetrakis-μ-acetato-bis(3-pyridylcarbinol)dicopper(II) monomethylenedichloride

Abstract The complex tetrakis-μ-acetato-bis(3-pyridyl-carbinol)dicopper(II) monoethylenedichloride, Cu 2 CH 3 COO) 4 (3-pycar) 2 ·CH 2 Cl 2 was synthesized, and spectral and magnetic data obtained. The crystal and molecular structure were determined from three-dimensional counter X-ray data. The complex crystallizes in the monoclinic space group P 2 1 / c with four formula units ( Z = 4) in a cell of dimensions a = 16.778) A, b = 19.853(14) A, c = 8.384(4) A, and β = 97.38(5)°. The observed and calculated densities are 1.598 g cm −3 . The structure was refined by blocked-cascade full-matrix least-squares methods to an R factor 0f 0.043 using 2509 independent intensities. The structure consist of two independent centrosymmetric tetra-carboxylato-bridged dimers with the 3-pyridyl-carbinol molecules (ronicol) in the axial positions. The CuCu, CuO eq (mean) and CuN ax distances in the two independent dimers are: 2.654(1), 1.963(4) and 2.197(5) A; 2.634(1), 1.969(4) and 2.152(5) A, respectively. The EPR spectrum of a polycrystalline sample of the complex revealed triplet state (S = 1) transitions. Variable temperature (93-293) K) magnetic measurements indicate an antiferromagnetic interaction of −2J = 330(8) cm −1 . The magnetic data and the X-ray crystallographic results, together with literature data, were used to determine the relationship between the donor ability of the axial ligands, the displacement of the copper(II) atoms from the basal plane towards the apical ligands, and the length of the CuCu bond.

SERINE, THREONINE AND α-HYDROXYAMINE COORDINATION TO CUPRIC IONS BY HYDROXYL-OXYGEN-METAL BONDS

Abstract The copper complexes of serine and threonine have been studied under a wide pH range. Results obtained by conductivity measurements, potentiometry, visible and EPR spectroscopy all indicate that hydroxyamino acids are coordinated in a tridentate fashion. Evidence is presented which shows that metal-alkoxy bonds are formed in basic solutions and that the deprotonated ligands then form anionic copper complexes.

Chrysotile asbestos fibres from Quebec: electron magnetic resonance identification

Abstract Quebec chrysotile asbestos fibres have been examined by EPR spectroscopy at room T and 77 K. Finely divided samples show an absorption due to manganese(II) at g = 2.0with a hyperfine coupling of 90 gauss. Several types of ferric ions are present in addition to magnetite. These include surface adsorbed hydroxides and lattice bound ions. From the EPR spectrum of structurally bound iron in long fibres oriented perpendicularly to the magnetic field, it was found that the ferric ions are in a rhombic environment. EPR thus shows promise as a tool for the identification and characterization of asbestos fibres.

EPR non-detectable copper in pyridoxal biogenic amine schiff base complexes

Abstract Schiff bases formed with octopamine, pyridoxal and pyridoxal phosphate react with copper ions to give various pH-dependent species. The outstanding feature of these complexes is their absence of EPR spectra at physiological pH values. We propose dimeric dipolar coupled structures for the EPR non-detectable copper complexes, involving hydroxyde anions and vitamin B-6 Schiff bases. These results establish that EPR non-detectable copper in enzymes may arise from dipolar coupling between metal ions involved in Schiff base type complexes.

LINEAR CHAIN FATTY DIACIDS: COPPER(II) COMPOUNDS

Abstract Copper(II) complexes of linear chain fatty diacids have been obtained in the solid state with diacids containing up to thirteen carbon atoms. The green compounds were studied by spectroscopic and magnetic methods. The results conform to an antiferromagnetically coupled dimer model which can be influenced by distortions in the carboxylate bridge structure. Thus the magnetic exchange parameter is at a maximum of 360 cm−1 in copper(II) adipate and decreases, as the chain length increases, to a value of 280 cm−1 in copper(II) brassylate. The hydrophobic methylene chains influence the inter-chain packing interactions at the polar carboxylate functions.

Mixed aldehyde condensations on copper glycinate

Abstract Glycine coordinated to cupric ions reacts in basic solution with a stoichiometric quantity of aldehydes to give β-hydroxyaminoacids. When the reaction contains a mixture of aldehydes, one of them being acetaldehyde, threonine is produced in the solution together with a variable amount of the bulkier substituted serine. An intermediate complex may be isolated which affords a larger proportion of substituted serines with predominance of the threo isomers. Acetaldehyde and benzaldehyde give a 66% yield of threo β-phenylserine.

A comparative study of cupric complexes of dicarboxylic acids and acid-amides ligands

Abstract A bis(succinamato)copper(II) complex has been synthetized as well as several cyclic acid-amide ligand complexes. These compounds were characterized by elemental and thermogravimetric analyses, infrared and EPR spectroscopies. Analogous dicarboxylic acids give complexes of 1/1 stoichiometry which are thermally more stable than the acid-amide complexes. All the reported compounds show triplet state EPR spectra similar to cupric acetate. There is no evidence for a participation of the amide functions in cupric ion complexation.

Theoretical and Experimental Study of Radial Concentration Profiles Originating from a Non Punctual Injection Source

Abstract Radial concentration profiles originating from non delta plug flow injection functions can be theoretically accounted for in terms of a Bessel function series. Results related to axial injections of various diameters relative to the column I.D. are described. They are in food agreement with the theory.

Synthesis of threonine and separation from its copper complex on an ion exchange resin

Abstract Threonine can be synthesised in better than 95% yields using the base catalysed condensation of acetaldehyde on a stoechiometric amount of the copper complex of glycine. A convenient removal of the metal ions via a cation exchange resin in the NH 4 + form gives a mixture of threonine and allothreonine (threo to erythro ratio 1.7:1.8). Electrodecomposition of the intermediate oxazolidine complex yields pure threonine.