Structure of the copper(II) complex of (S-.beta.-(2-pyridylethyl)-L-cysteine (original) (raw)
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Inorganica Chimica Acta, 1998
The twoepimersof P-cyclodextrin 6-functionalized with L-orn-cysteine (6-S-( I.)-cysteine-6.deoxy-P-cyclodextinand (6-S-( u)-cysteine-6-deoxy-P-cyclodextrin 1 were synthesized. Their binary and ternary coppert II) complexes with amino acids were characterized by electronic, circular dichroism and BSR spectroscopies. The binary copper(H) complexes were used as eluents in ligand exchange chromatography to test their ability 10 resolve rncemclte mixtures of unmodified amino acids. High performance liquid chromatography separation of ~/wTrpO~' was nchicvcd only when Ihe complex of the I>-cysleine derivative was used as the eluent. 0 1998 Blsevier Science S.A. All rights reserved. * Cnrresponding uuthor. Tel.: + 39-95-330 533: fax: -t= 39-95-580 138. 0020-1693/9R/$l9.OU 0 1998 Elsevter Science S.A. All rights reserved. fWSOO20-1693(97)06139-2 'H NMR (200 MHz, D&I) t% 5.09 t cl, 1H. IA. J In.2n=3.8L S.02 (d. 6H. I-H),4,@-3.75 (m. 2SH. 3-. 6-, 5-H and CH ofcystcine ), X67-3.45 ( m, 14H, 2-,4-H 1.3. I&-2.W (m, 4H, 6-A, and CH: of cyst&e J,,.,% J ,\,s = 4.0 Hz).
Inorganic Chemistry, 1981
A blue and a green compound of the type Cu(Ac-@-ala),.2H20 and [C~(Ac-@-ala)~~H~0]~~2H~O (Ac-@-ala = Nacetyl-8-alaninato ion) and a green compound of the type [C~(Ac-@-ala)~]~ (obtained by dehydrating the two compounds above mentioned) were prepared and characterized by means of room-temperature electronic and infrared spectroscopy, low-and room-temperature magnetic and EPR measurements and DSC analysis. For the blue and green hydrate compounds the crystal structure was also determined by single-crystal X-ray diffraction methods. The blue C~(Ac-@-ala)~-2H,O complex crystallizes in the monoclinic space group P2,ln with two molecules in a unit cell of dimensions u = 5.0135 (2) A, b = 8.415 (1) A, c = 17.952 (2) A, 8 = 91.186 (3)O, ddd = 1.58 g ~m-~, and dm4 = 1.59 g ~m-~. Least-squares refinement of the 137 variables led to a value of the conventional R index of 0.062 for 1353 independent reflections having I > 241). The copper environment consists of two centrosymmetrically related carboxylic oxygens and two water molecules in a square-planar arrangement. Two weak interactions involving the uncoordinated carboxylic oxygen atoms complete the coordination to a severely distorted tetragonal bipyramid. The green [Cu(A~-@-ala)~.H~0]~~2H~O complex crystallizes in the monoclinic space group P2'/c with two molecules in a unit cell of dimensions u = 9.120 (1) A, b = 18.527 (3) A, c = 8.978 (3) A, @ = 98.61 (l)', dd = 1.59 g ~m-~, and d-= 1.59 g c r~~~. Least-squares refinement of the 226 variables had led to a value of the conventional R index of 0.068 for 2509 independent reflections having I > 2 4 4. The structure consists of centrosymmetric dimeric units. Coordination around each metal atom is elongated octahedrally with the carboxyl oxygen atoms at the equatorial sites and a water molecule and a copper atom in the axial positions. The importance of hydrogen bonding in the packing of the molecules is also discussed. These complexes represent an example of structural isomerism depending on the influence of the solution media. The spectroscopic and magnetic properties are interpreted on the basis of the crystal structures, in particular the hydrate and anhydrous green compounds, which present similar physical properties, show an exchange integral (-24 of 324 f 15 and 285 & 15 cm-I, respectively, and show a zero field splitting D of 0.37 cm-I. The thermal extrusion of two water molecules from the blue compound is accompanied by a structural change (irreversible thermochromism).
Journal of Mass Spectrometry, 2005
The structure and energetics of complexes obtained upon interaction between cysteine and Zn 2+ , Cd 2+ , Hg 2+ and Cu 2+ cations were studied using quantum chemical density functional theory calculations with the 6-311++G * * orbital basis set and relativistic pseudopotentials for the cations. Different coordination sites for metal ions on several cysteine conformers were considered. In their lowest energy complexes with the amino acid, the Zn 2+ and Cd 2+ cations appear to be three-coordinated to carbonyl oxygen, nitrogen and sulfur atoms, whereas the Cu 2+ and Hg 2+ ions are coordinated to both the carbonyl oxygen and sulfur atoms of one of the zwitterion forms of the amino acid. Bonds of metal cations with the coordination sites are mainly ionic except those established with sulfur, which show a small covalent character that become most significant when Cu 2+ and Hg 2+ are involved. The order of metal ion affinity proposed is Cu > Zn > Hg > Cd.
On the structure, infrared and Raman spectra of the 2:1 cysteine–Zn complex
Theoretical Chemistry Accounts, 2010
A recent study on the Raman spectrum of the cysteine zwitterion and anion, and the 2:1 (Cys) 2 Zn complex was reanalyzed employing B3LYP/6-311??G (3df,2pd) calculations in a simulated water environment. The spectra were rediscussed in light of the apparent incorrect structure determined in the original paper for this complex. The complex turns out to be tetrahedral and tetracoordinated instead of octahedral hexacoordinated, as initially proposed. The calculated Raman spectrum of the complex agrees very well with the experimental data, showing that both the geometrical and electronic structures are well represented. Three metal-ligand bands are found, two of them involving mostly the symmetrical and asymmetrical stretching of the Zn-N and Zn-S bonds. They were measured at 334 and 296 cm -1 and calculated at 319 and 249 cm -1 , respectively. The third band involves the stretching of Zn-S bonds but also skeletal vibrations of the ligand. This band, measured at 399 cm -1 and calculated at 444 cm -1 , has been previously assigned incorrectly to a Zn-O bond which does not actually exists since the CO 2 -1 fragments are located away from the Zn ion.
Inorganica Chimica Acta, 2002
Copper(II) tetrakis-complexes of cytosine (cyt), 1-methylcytosine (1-mcyt) and cytidine (cyd) have been isolated and their spectral and electrochemical properties investigated. The X-ray crystal structure of tetrakis(1-mcyt)copper(II) perchlorate dihydrate has been successfully determined. The coordination geometry around copper in the complex corresponds to square-based 4'/4? coordination. In addition to the preferential Cu Ã/N3 bonds, there is significant interaction between copper(II) and the exocyclic O2 of 1-mcyt rings. The mutually cis 1-mcyt rings are present in a head-tail-head-tail arrangement, which is stabilised by a network of bifurcated hydrogen-bonding between the exocyclic amine hydrogen atoms and the oxygen atoms of the adjacent carbonyl groups. The aqueous solution spectra of the complexes are slightly different from solid state spectra revealing that the solid state structures undergo slight changes on dissolution in water. The electronic and EPR spectral and electrochemical results are consistent with the retention of the solid state structure even in solution. The EPR spectra exhibit N-superhyperfine lines corresponding to the coordination of four N3 atoms of cytosines. The higher g values indicate decreased covalency in the metal Ã/ligand bond and the range of g /A quotient (119 Á/121 cm) confirms the presence of CuN 4 square-planar coordination geometry even in solution. The plot of i pc and E 1/2 values versus 1-mcyt concentration for the electrochemical titration of Cu(ClO 4) 2 with 1-mcyt reveals an inflection point indicating the formation of 1:4 species in solution. The trend in E 1/2 values of the complexes shows that the incorporation of electron releasing methyl group/ribose moiety at N1 position of cytosine ring enhances the stabilisation of Cu(II), in spite of the steric demand from O Ä/C2.
Polyhedron, 2001
The formation constants and the isotropic ESR parameters (g-factors, 63 Cu, 65 Cu, 14 N hyperfine coupling constants and relaxation parameters) of the various species were determined by the simultaneous analysis of a series of spectra, taken in a circulating system at various pH and ligand-to-metal concentration ratio. For both systems the new [CuLH] 2 + complex was identified in acidic solutions. With the glycyl-L-serine ligand below pH 11.5 the same complexes and coordination modes are formed than with simple dipeptides. The side-chain donor group is bound only over pH 11.5 in the complex [CuLH − 2 (OH)] 2 − , where it is deprotonated and substitutes the carboxylate O in the third equatorial site. For the bis complex [CuLH − 1 (L)] − an isomeric equilibrium was shown, where the difference between the isomers was based on which of the donor atoms of the 'L' ligand, the peptide O or the amino N, occupies the fourth equatorial position, and which one is coordinated axially. The L-seryl-glycine ligand forms the same species as simple dipeptides and glycyl-L-serine up to pH 8. The only difference is that the axial binding of the alcoholic OH group fairly stabilizes the bidentate equatorial coordination of the 'L' ligand through the amino N and peptide O atoms in the [CuL] + complex as well as in the major isomer of the [CuLH − 1 (L)] − complex. For this system we showed that (1) proton loss and the equatorial coordination of the alcoholic OH group occurs at relatively low pH (over pH 8-9), which results in the [CuL 2 H − 2 ] 2 − complex with excess ligand, and also the newly identified species [Cu 2 L 2 H − 4 ] 2 − : (2) this process is in competition with the proton loss of a coordinated water molecule. For both systems, the ESR-inactive species [Cu 2 L 2 H − 3 ] − was also shown.
Complexation Studies of N, N′-ethylenedi-L-cysteine with Some Metal Ions
Journal of Solution Chemistry, 2009
As part of a search for environmentally friendly metal chelating ligands, the stability constants of N, N -ethylenedi-L-cysteine (EC) complexes with Ca(II), Cu(II), Mg(II) and Mn(II) were determined by potentiometry with a glass electrode in aqueous solutions containing 0.1 mol·L −1 KCl at 25°C. Final models are proposed. For the Ca(II)-EC system, the overall stability constants are log 10 β CaHL = 14.53 ± 0.03, log 10 β CaL = 4.79 ± 0.01 and log 10 β CaL2 = 8.38 ± 0.04. For the M(II)-EC systems, where M = Cu(II) or Mg(II), the overall stability constants are log 10 β CuHL = 31.19 ± 0.02 and log 10 β CuL = 27.02 ± 0.06 for Cu(II), and are log 10 β MgHL = 14.84 ± 0.02 and log 10 β MgL = 6.164 ± 0.008 for Mg(II). For the Mn(II)-EC system, the overall stability constant is log 10 β MnL = 10.12 ± 0.01.