Search results for "copper"
showing 10 items of 3029 documents
Effect of the hydrophobic spacer in bonded [Cu(l-hydroxyprolyl)alkyl]+ silicas on retention and enantioselectivity of α-amino acids in high-performan…
1983
Abstract The following chiral ligands were bonded to silica: [Cu( l -hydroxyprolyl)methyl) + on LiChrosorb Si 60 (1), [Cu( l -hydroxyprolyl)methyl] + on LiChrosorb Si 100 (2) and [Cu( l -hydroxyprolyl) n -octyl] + on LiChrosorb Si 100 (3). The packings contained residual iodomethyl- and ω-iodooctyl groups at the surface. Studies on packing 1 and 2 under comparable conditions in eluents containing 10 -4 M copper acetate showed a higher retention on 1 than on 2 but a much better enantioselectivity in the latter case. The retention of enantiomers on all packings examined was found to be governed by the eluent pH and methanol content as well as by the concentration of ammonium acetate. The vari…
Flow-injection spectrophotometric determination of amino acids based on an immobilised copper(II) -zincon system
1993
Abstract The flow-injection spectrophotometric determination of different amino acids was carried out by reaction with copper(II) ions entrapped in a polymeric material and filling a packed-bed reactor; the released copper(II), complexed with the amino acid, reacted with zincon in a basic medium producing a blue colour that was monitored at 600 nm. The method was applied to determine the contents of different amino acids in pharmaceutical formulations. The calibration graph for glycine was linear over the range 0.5–20 μg ml −1 with a relative standard deviation of 0.8% ( n = 6) at 10 μg ml −1 and a sample throughput of 108 h −1 .
Reactivity of CuI and CuBr toward Et2S: a reinvestigation on the self-assembly of luminescent copper(I) coordination polymers.
2010
CuI reacts with SEt(2) in hexane to afford the known strongly luminescent 1D coordination polymer [(Et(2)S)(3){Cu(4)(mu(3)-I)(4)}](n) (1). Its X-ray structure has been redetermined at 115, 235, and 275 K in order to address the behavior of the cluster-centered emission and is built upon Cu(4)(mu(3)-I)(4) cubane-like clusters as secondary building units (SBUs), which are interconnected via bridging SEt(2) ligands. However, we could not reproduce the preparation of a coordination polymer with composition [(Et(2)S)(3){Cu(4)(mu(3)-Br)(4)}](n) as reported in Inorg. Chem. 1975, 14, 1667. In contrast, the autoassembly reaction of SEt(2) with CuBr results in the formation of a novel 1D coordination…
ChemInform Abstract: Enantioselective Addition of Nitromethane to α-Keto Esters Catalyzed by Copper(II)-Iminopyridine Complexes.
2008
The copper complex of a chiral iminopyridine easily prepared from (R)-(−)-fenchone and picolylamine catalyzes the enantioselective Henry (nitroaldol) reaction between nitromethane and α-keto esters. Good yields and modest to good enantioselectivities are obtained for a wide range of α-keto esters, bearing aromatic, alkyl or alkenyl groups attached to the ketone carbonyl group.
Large Scale Synthesis of Mono- and Di-urethane Derivatives of Lysine.
1999
Orthogonally protected diurethane derivatives of lysine are valuable materials for peptide syntheses. An example is ZLys(Boc), which is exploited in the industrial production of certain well-established peptide drugs. 3,4) Another derivative is Fmoc-Lys(Boc), which is in common use in the laboratory synthesis of peptides. 5) The simplest route to these lysine derivatives seems to be using the copper complex for simultaneous protection of the a-amino and a-carboxyl function, N e -tert-butoxycarbonylation and then copper detachment. The obtained Lys(Boc) might be then subjected to N a -benzyloxycarbonylation.
Three-Dimensional Mixed-Ligand Coordination Polymers with Ferromagnetically Coupled Cyclic Tetranuclear Copper(II) Units Bonded by Weak Interactions
2011
The complexes {[Cu(HGLYO)(NO3)(bpy)]·H2O}4 (1), {[Cu(HGLYO)(NO3)(phen)]·H2O}4 (2), and [Cu(HLACO)(ClO4)(phen)]4 (3) (bpy is 2,2′-bipyridine, phen is 1,10-phenanthroline, HGLYO is monoanionic glycol...
Screening of ligands for the Ullmann synthesis of electron-rich diaryl ethers
2012
In the search for new ligands for the Ullmann diaryl ether synthesis, permitting the coupling of electron-rich aryl bromides at relatively low temperatures, 56 structurally diverse multidentate ligands were screened in a model system that uses copper iodide in acetonitrile with potassium phosphate as the base. The ligands differed largely in their performance, but no privileged structural class could be identified.
Copper complexes with dithiocarbamates derived from natural occurring amino acids. Crystal and molecular structure of [Cu(en)(EtOH)(H2O)3][Cu(dtc-pro…
2002
Abstract Reaction of Cu(II) salts with dithiocarbamates derived from the amino acids asparagine, glutamine, serine, threonine and tyrosine leads to reduction of the metallic cation and formation of Cu(I) complexes, whereas reaction with proline dithiocarbamate takes place without reduction, leading to formation of a Cu(II) coordination compound. Simultaneous reaction of proline dithiocarbamate and ethylenediamine with Cu(II) leads to the formation of the mixed complex [Cu(en)(EtOH)(H2O)3][Cu(dtc-pro)2]. In the anion, the Cu(II) centre possesses a D2h local symmetry, coordinated by two bidentate dithiocarbamate ligands, while the Cu(II) centre is in a distorted octahedral coordination in the…
Self-assembly of a chiral three-dimensional manganese(II)-copper(II) coordination polymer with a double helical architecture
2013
The use of the anionic dicopper(ii) complex, [CuII(mpba) 2]4- [mpba = N,N′-1,3-phenylenebis(oxamate)], as tetrakis(bidentate) metalloligand toward MnII ions in the presence of oxalate and the chiral (S)-trimethyl-(1-phenylethyl)ammonium cation affords the first example of a mixed oxalato/oxamato-based chiral 3D metal-organic polymer. © 2013 The Royal Society of Chemistry.
New dinuclear copper complexes incorporating bis(imidazolyl) based ligands and bidentate–monodentate oxalate bridges. Crystal structure and magnetic …
2016
Abstract This paper reports the synthesis, X-ray crystal structure and magnetic characterization of two novel copper(II) dinuclear compounds including bis(imidazolyl) ligands and oxalate anions, [Cu2(BIM)2(C2O4)2]·4H2O (1) (BIM = bis(2-imidazolyl)methane) and [Cu2(BIK)2(C2O4)2] (2) (BIK = bis(2-imidazolyl)ketone). The oxalate anion acts as bidentate–monodentate in both cases, although it exhibits different coordination bridging modes: whereas in compound 1 a μ1,1,2-oxalato is observed, a μ1,2,3-oxalato is found in compound 2. In both cases, the 3D framework is held together by a combination of H-bonding and aromatic-aromatic interactions provided by the convenient structural features of BIM…