Magnetic Resonance Studies on Copper(II) Complex Ions in Solution. I. Temperature Dependences of the 17O NMR and Copper(II) EPR Linewidths of Cu(H2O)62+

Lewis, W. B.; Alei, Mohammed; Morgan, L. O.

doi:10.1063/1.1727057

Cited by 106 publications

(44 citation statements)

References 25 publications

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“…2 + complex. [30][31][32] The ratio of the two different types of EPR signals was determined by a subtraction and integration procedure for each separate signal. Such an estimation (within 10 % accuracy) shows that fully hydrated complex 2 (x = 7.3) consists of 40 % of the dry Cu II dendrimeric complex and 60 % of the [Cu-…”

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confidence: 99%

Magnetic Properties of Poly(propylene imine)–Copper Dendromesogenic Complexes: An EPR Study

et al. 2006

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Copper(II) complexes formed by coordination of the Cu(II) ion with liquid-crystalline poly(propylene imine) dendrimer ligand (L) of the first (complex 1) and second (complex 2) generations with various Cu(II) contents (x = Cu/L) have been studied by electron paramagnetic resonance (EPR) spectroscopy. The existence of a redox-active blue complex 1 (x = 1.9) and the copper(II) nitrate electron transfer associated with the valence tautomerism are revealed for the first time in copper-based dendrimers. It has been shown that the electronic structure of the blue complex 1 (x = 1.9) is adequately described as a mixed-valence dimer containing d9- and diamagnetic d10-configurated copper ions, and an antiferromagnetically coupled NO3* radical arising on the nitrate-bridged counter ligand. The activation energy value found for the electron transfer is about 0.35 meV, which indicates a low-energy charge dynamic. The ability of the blue and green complexes 1 (x = 1.9) dissolved in isotropic solvents to orient themselves in the magnetic field was revealed by EPR spectroscopy. The degree of orientation of the molecular z axis (S(z)) of these complexes in the magnetic field differs, depending on the type of copper(II)-complexing site in the dendrimer ligand, and can reach 0.76, which is close to S(z) = 1 (completely aligned system). A combination of magnetic and orientational parameters indicates an NO4 environment of the Cu(II) ion in green complex 1 (x = 1.9), and confirms the chain structure with intermolecular Cu(II)-NO3-Cu(II) bridges between Cu(II) centres in columns.

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confidence: 99%

Magnetic Properties of Poly(propylene imine)–Copper Dendromesogenic Complexes: An EPR Study

et al. 2006

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“…The coordinating amino acid atoms lie approximately in the equatorial plane and the copper is just above this plane. EPR studies on PrP (23)(24)(25)(26)(27)(28) and an 15 N-labeled analogue have demonstrated that the Cu-HGGGW structure is maintained in the full prion protein octarepeat domain [20]. The S100 proteins are non-covalent homodimers.…”

Section: Introductionmentioning

confidence: 99%

“…Cu(aq) 2+ has been shown by EPR to be tetragonally distorted [23]. A recent study of Cu(aq) 2+ in solution combining a full multiple-scattering analysis of the copper Kedge X-ray absorption spectrum and density functional theory indicated that it is an elongated five-coordinate square pyramid with four C-O eq bonds and a long Cu-O ax bond [24].…”

Section: Introductionmentioning

confidence: 99%

“…The copper(II) complexes copper(II) aqua, Cu(aq) 2+ ; copper(II) hydroxide, Cu(OH) 4 2− [17]; copper(II) ethylenediaminetetraacetate, CuEDTA [18]; copper(II) tetraimidazole, CuIm 4 [19]; copper(II) tetra-2-methylimidazole, CuMeIm 4 [19]; prion peptide sample Cu-HGGGW [20]; prion protein sample PrP (23)(24)(25)(26)(27)(28) [21]; and S100 type proteins [Cu(II)-S100A12 and Ca(II)-S100B and Cu(II)-S100B] [22] which have relatively well-defined copper centers were chosen for study.…”

Section: Introductionmentioning

confidence: 99%

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Electron spin relaxation of copper(II) complexes in glassy solution between 10 and 120K

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Fox

Millhauser

et al. 2006

Journal of Magnetic Resonance

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The temperature dependence, between 10 and 120 K, of electron spin-lattice relaxation at X-band was analyzed for a series of eight pyrrolate-imine complexes and for ten other copper(II) complexes with varying ligands and geometry including copper-containing prion octarepeat domain and S100 type proteins. The geometry of the CuN 4 coordination sphere for pyrrolateimine complexes with R = H, methyl, n-butyl, diphenylmethyl, benzyl, 2-adamantyl, 1-adamantyl, and tert-butyl has been shown to range from planar to pseudo-tetrahedral. The fit to the recovery curves was better for a distribution of values of T 1 than for a single time constant. Distributions of relaxation times may be characteristic of Cu(II) in glassy solution. Long-pulse saturation recovery and inversion recovery measurements were performed. The temperature dependence of spinlattice relaxation rates was analyzed in terms of contributions from the direct process, the Raman process, and local modes. It was necessary to include more than one process to fit the experimental data. There was a small contribution from the direct process at low temperature. The Raman process was the dominant contribution to relaxation between about 20 and 60 K. Debye temperatures were between 80 and 120 K. For samples with similar Debye temperatures the coefficient of the Raman process tended to increase as g z increased, as expected if modulation of spin-orbit coupling is a major factor in relaxation rates. Above about 60 K local modes with energies in the range of 260-360 K (180-250 cm −1 ) dominated the relaxation. For molecules with similar geometry, relaxation rates were faster for more flexible molecules than for more rigid ones. Relaxation rates for the copper protein samples were similar to rates for small molecules with comparable coordination spheres. At each temperature studied the range of relaxation rates was less than an order of magnitude. The spread was smaller between 20 and 60 K where the Raman process dominates, than at higher temperatures where local modes dominate the relaxation.Spin echo dephasing time constants, T m , were calculated from two-pulse spin echo decays. Near 10 K T m was dominated by proton spins in the surroundings. As temperature was increased motion and spin-lattice relaxation made increasing contributions to T m . Near 100 K spin-lattice relaxation dominated T m .

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“…where a is the line width contribution due to nonmotional effects and to spinrotation mechanism [28] and the a', ,8, and ~, are expressed in terms of the g and A tensor anisotropies and of the spectral densities, which contain the correlation time for the modulation motion, r c. In many cases this time is defined as the Debye-Stokes-Einstein rotational correlation time [29][30][31][32]:…”

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confidence: 99%

Nucleoside-copper(II) system in water and on 13X-zeolite studied by continuous-wave and pulsed-wave ESR

et al. 2003

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In order to study the effects of large-surface-area solids on the formation of biomacromolecules, copper(II)-nucleosides complexes were studied in water at high pH and after contact with the cavity walls of 13X-zeolite. The results were mainly colIected by electron spin resonance in continuous (cw-ESR) and pulsed (ESE) wave. Particular attention was dedicated to adenosine as a nucleoside model for the formation of compounds which were fully characterized in alkaline water solution and after adsorption on commercial 13X-zeolite. In aqueous solution, adenosine was coordinated to copper(II) through deprotonated hydroxyl groups in the 2' and 3' positions of the ribose unit, with the formation of lCu(adenosine)z(HzO)2] 2-. When adsorbed on zeolite, both cw-ESR and ESE showed that a fraetion of the adsorbed complexes did not change their structure and showed high mobility in the zeolite faujasite cavity. The remaining fraction directly interacted with 27A1 nuclei of the zeolite framework. Other copper(lI)-nucleosides behaved in the same manner. Surprisingly enough, alkaline solutions of nuc[eos~des were able to remove copper([l) from zeolite in the forro of [Cu(adenosine)2(H20)2] 2-which free[y moved in the supematant aqueous liquid.

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Magnetic Resonance Studies on Copper(II) Complex Ions in Solution. I. Temperature Dependences of the 17O NMR and Copper(II) EPR Linewidths of Cu(H2O)62+

Cited by 106 publications

References 25 publications

Magnetic Properties of Poly(propylene imine)–Copper Dendromesogenic Complexes: An EPR Study

Magnetic Properties of Poly(propylene imine)–Copper Dendromesogenic Complexes: An EPR Study

Electron spin relaxation of copper(II) complexes in glassy solution between 10 and 120K

Nucleoside-copper(II) system in water and on 13X-zeolite studied by continuous-wave and pulsed-wave ESR

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