共查询到20条相似文献,搜索用时 0 毫秒
1.
E. Forizs L. David O. Cozar V. Chiş C. Craciun R. Tetean M. Todica 《Applied magnetic resonance》1999,16(4):499-506
The CuL2X2 (L = 7-chlor-l,3-dihydro-3-hydroxi-5-phenyl-2H-l,4-benzodiazepin-2-one, also known as oxazepam, X = Cl, Br) complexes were prepared and investigated by ESR (electron spin resonance) method. Powder ESR spectra of CuL2X2 compounds at room temperature show the presence of monomeric species having an axial symmetry with a small rhombic distortion. In case of compounds with Cl there is a superposition of two nonequivalent mononuclear species, one with adx2 - y2 d_{x^2 - y^2 } ground state and another with adz2 d_{z^2 } ground state. In pyridine (Py) and dimethylformamide (DMF) solutions the monomeric species prevail. Two different monomeric species, one with pseudotetrahedral (Td) and the other with elongated tetrahedral-octahedral symmetry, were evidenced in DMF solutions adsorbed on NaY zeolite. In Py-DMF solutions two monomeric species were also identified. Dimeric species appear in DMF and Py solutions adsorbed on NaY zeolite through the coordination of two Cu(II) ions at the same keto-oxygen from one oxazepam molecule. 相似文献
2.
L. David O. Cozar L. Sumâlan V. Chis R. Tetean C. Crâciun 《Applied magnetic resonance》1997,13(3-4):571-577
The Cu(II) complexes with 2-N-acetyl-salicylidene-hydrazino-4-chlor-methyl thiazole (L.) and 2-N-acetyl salicylidene-hydrazioo-4-thiazolyl acetic ester (LII) were prepared and investigated by ESR measurements. The powder ESR spectrum at room temperature of CuLIICl is quasi-isotropic (g=2.113), while for CuLIICl is characteristic of monomeric species with axial symmetry (g II)=2.234,g 1=2.073). The isotropic ESR spectra of the CuLCl compounds in DMSO solution suggest the presence of pseudo-tetrahedral monomeric species. The anisotropic spectra were obtained for adsorbed CuLCl DMSO solutions on NaY zeolite. The parallel hyperfine structure shows the coexistence of two magnetic nonequivalent monomeric species. The estimation of some LCAO-MO coefficients using Kivelson and Neiman’s approximation reveals a dominant ionic character for copper-ligand bonds. 相似文献
3.
C. G. Palivan H. M. N. Palivan B. A. Goodman C. Cristescu 《Applied magnetic resonance》1998,15(3-4):477-488
Electron paramagnetic resonance (EPR) spectroscopy and molecular dynamics calculations have been used to compare the chemical environments of Cu(II) in three substituted asymmetric-triazine (as-triazine) complexes with a closely related complex that was reported previously to have Superoxide dismutase (SOD) and antiviral activities. The structure most strongly associated with the biological activity appears to be planar with two 6-membered chelate rings having 2N2O coordination around the copper atom. 相似文献
4.
Jagdish Prasad Vijai Krishna Hira Lal Nigam 《Journal of Physics and Chemistry of Solids》1977,38(10):1149-1152
The X-ray K-absorption edge position and the extended fine structure of copper in some copper(II) carboxylate complexes involving metal-metal exchange interaction have been investigated using a 40 cm bentcrystal spectrograph. It has been found that the edge position in these complexes shifts towards the higher energy side as the pKa value of the corresponding acids increases. Sharp and narrow main peaks have been observed in all these complexes except the monomeric complex, copper(II) trichloroacetate. Estimates of metal-ligand average bond distances have also been made. 相似文献
5.
N. E. Domracheva A. Mirea M. Schwoerer L. Torre-Lorente G. Lattermann 《Physics of the Solid State》2007,49(7):1392-1402
New nanostructured materials, namely, the liquid-crystalline copper(II) complexes that contain poly(propylene imine) dendrimer ligands of the first (ligand 1) and second (ligand 2) generations and which have a columnar mesophase and different copper contents (x = Cu/L), are investigated by EPR spectroscopy. The influence of water molecules and nitrate counterions on the magnetic properties of complex 2 (x = 7.3) is studied. It is demonstrated that water molecules can extract some of the copper ions from dendrimer complexes and form hexaaqua copper complexes with free ions. The dimer spectra of fully hydrated complex 2 (x = 7.3) are observed at temperatures T < 10 K. For this complex, the structure is identified and the distance between the copper ions is determined. It is shown that the nitrate counterion plays the role of a bridge between the hexaaqua copper(II) complex and the dendrimer copper(II) complex. The temperature-induced valence tautomerism attended by electron transport is revealed for the first time in blue dendrimer complexes 1 (x = 1.9) with a dimer structure. The activation energy for electron transport is estimated to be 0.35 meV. The coordination of the copper ion site (NO4) and the structural arrangement of green complexes 1 (x = 1.9) in the columnar mesophase are determined. Complexes of this type form linear chains in which nitrate counterions serve as bridges between copper centers. It is revealed that green complexes 1 (x = 1.9) dissolved in isotropic inert solvents can be oriented in the magnetic field (B 0 = 8000 G). The degree of orientation of these complexes is rather high (S z = 0.76) and close to that of systems with a complete ordering (S z = 1) in the magnetic field. Copper(0) nanoclusters prepared by reduction of complex 2 (x = 7.3) in two reducing agents (NaBH4, N2H4 · H2O) are examined. A model is proposed for a possible location of Cu(0) nanoclusters in a dendrimer matrix. 相似文献
6.
7.
Prof. Dr. Onuc Cozar V. Znamirovschi L. David L. Giurgiu J. Zsako 《Applied magnetic resonance》1992,3(5):849-857
The following copper(II)-dioxime-dichloride compounds: [Cu(G)Cl2]2, [Cu(P)Cl2]2, [Cu(DMG)Cl2]2 and [Cu(O)Cl2]2 (where G=C2H4O2N2, P=C3H6O2N2, DMG=C4H8O2N2, O=C8H14O2N2) were investigated by ESR method. Spectra of powder samples obtained in the g?2 region suggest the presence of triplet ground state (S=1) realized by a weak ferromagnetic exchange coupling. In liquid and frozen solutions the monomeric species (S=1/2) prevail. Some delicate changes in the coordination polyhedra symmetry in terms of ligand molecules and solvents nature were evidence. A 4p-admixture degree of 2% in the dxy ground state was estimated for pseudotetrahedral (Td) species in frozen solutions. 相似文献
8.
9.
《Journal of Magnetic Resonance (1969)》1982,46(3):361-373
ENDOR spectra were obtained from 63Cu and 65Cu nuclei in bis(2,4-pentanedionato)copper(II) doped in bis(2,4-pentanedionato)palladium(II) single crystals. The copper hyperfine and nuclear quadrupole coupling constants determined from the ENDOR spectra are compared to those obtained previously by EPR. The nuclear quadrupole coupling tensor obtained from ENDOR reveals deviation from the axial symmetry. It is shown that the asymmetry may arise from interaction with the field gradient attributable to the charges on the ligand. 相似文献
10.
A. A. Beznishchenko V. G. Makhan’kova N. A. Davidenko I. I. Davidenko V. N. Kokozei A. N. Popenaka 《Journal of Applied Spectroscopy》2007,74(4):533-536
We studied the effect of an electric field on the transmission of linearly polarized light through films of composites based
on polyvinylbutyral doped with particles of Cu(II)/Mn(II) complexes with “skeleton” and “planar” structures. The action of
an electrostatic field causes light absorption to become anisotropic. The effect increases with increasing distance between
the cation and anion. Its sign reverses if the spatial structure of the complex is changed. A phenomenological model is proposed
according to which the electrooptical properties of the composites are due to a change in the mutual orientation of complex
building blocks on exposure to an external electric field.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 4, pp. 481–484, July–August, 2007. 相似文献
11.
Electron paramagnetic resonance (EPR) spectrometry and molecular mechanics force field calculations have been performed on some sterically hindered copper(II) complexes with hydrazonotriazine ligands, in order to gain further insight into the relationship between their bonding, structures and biological activity. As was the case with Cu(II) bis(hydrazono-triazine) complexes studied previously, the most stable configuration for all of the complexes involves coordination of two nitrogen and two oxygen atoms (2N2O) in a distorted tetragonal arrangement. With the present complexes, however, the superoxide radical scavenging activities were very low, a result which may be explained by their inability to form a (nearly) square planar structure, which facilitates the copper redox cycling during superoxide dismutation. 相似文献
12.
R. V. Gulyaev N. A. Kryuchkova L. N. Mazalov A. I. Boronin T. V. Basova V. A. Plyashkevich 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2011,5(1):48-56
The charged states of atoms in unsubstituted copper(II) phthalocyanine (CuPcH16) and hexade-cafluorinated copper(II) phthalocyanine (CuPcF16) complexes and in thin films of them deposited on silicon substrates by vacuum thermal evaporation are investigated by X-ray
photoelectron spectroscopy (XPS). The C(1s), N(1s), Cu(2p) core level energies and the charged states of atoms in the studied complexes are calculated using the DFT method. The performed
experimental study and theoretical calculations show that the introduction of electron acceptor substituents into benzene
rings mostly affects the atoms of benzene rings and insignificantly affects the charge state of nitrogen atoms in the pyrrole
ring. 相似文献
13.
D.C. Frost C.A. McDowell R.L. Tapping 《Journal of Electron Spectroscopy and Related Phenomena》1975,6(5):347-355
Satellite structure in the X-ray photoelectron (Cu 2p) spectra of some squareplanar cupric complexes has been compared to electron paramagnetic resonance and electronic spectra results on the electronic structure of these complexes. It is shown that these satellites can be assigned to various ligand → metal 3d or ligand → ligand* transitions within the monopole selection rules of the sudden approximation. 相似文献
14.
Abhijeet Gaur B. D. Shrivastava K. Srivastava J. Prasad Sandeep K. Singh 《X射线光谱测定》2012,41(6):384-392
X‐ray absorption fine structure spectra have been investigated at the K‐edge of copper in copper(II) salen/salophen complexes: [Cu(salen)] (1), [Cu(salen)CuCl2].H2O (2), [Cu(salophen)] (3) and [Cu(salophen) CuCl2].H2O (4), where salen2? = N,N′‐ethylenebis (salicylidenaminato); salophen2? = o‐phenylenediaminebis(salicylidenaminato). Complexes 1 and 3 are supposed to have one type of copper centers (called (Cu1)) and complexes 2 and 4 two types of copper centers (called (Cu1) and (Cu2)) having different coordination environments and geometries. A theoretical model has been generated using the available crystallographic data of complex 1 and it has been used for analysis of the extended X‐ray absorption fine structure (EXAFS) data of the four complexes to obtain the structural parameters for (Cu1) center. For this center, the obtained Cu–Cu distance (3.2 Å) verifies the binuclear nature of all the complexes. For determining the coordination geometry around (Cu2) center in 2 and 4, a theoretical model has been generated using the crystal structure of a Cu(II) complex, [Cu(C16H12N2O2Cl2)]. This theoretical model has been fitted to the EXAFS data of 2 and 4 to obtain the structural parameters for (Cu2) center. The present analysis shows that (Cu1) center has square pyramidal geometry involving 2N and 3O donor atoms, whereas (Cu2) center has distorted tetrahedral geometry with 2O and 2Cl donor atoms. The values of the chemical shifts and presence of typical Cu(II) X‐ray absorption near‐edge spectroscopy features suggest that copper is in the +2 oxidation state in all these complexes. The intensity of ls → 3d pre‐edge feature has been used to investigate the geometry and binuclear nature of the complexes. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
15.
Fourier analysis of EPR spectra is used to achieve straightforward discrimination between an even or odd number of nitrogen nuclei bound to copper in solution. The method is tested on a copper (II) dipeptide (Cu-HistidylGlycine) complex to confirm the room temperature structural arrangement previously hypothesized by conventional techniques. Any residual uncertainty about ligand coordination around copper in solution is eliminated by the present approach. This simple straightforward method is particularly useful for extracting information from poorly resolved patterns of room temperature EPR spectra. 相似文献
16.
G. K. Zahariou E. Gavrielatos I. M. Kalogeras G. Athanasellis A. Vassilikou-Dova O. Igglessi-Markopoulou 《辐射效应与固体损伤》2013,168(6-12):1057-1062
The 3-acyl tetramic acids constitute a growing class of natural products displaying a range of biological activities. The g , g ' tricarbonyl moiety present in the 3-acyl tetramic acid provides a suitable site for bidentate complexation to a metal, which increases the biological activity. For the dielectric study of N-acetyl-3-butanoyl tetramic acid and a series of its complexes with Cu(II) and Co(II) in symmetric and asymmetric forms, we used the Thermally Stimulated Depolarization Currents (TSDC) technique. The drastic decrease of the intensity of the TSDC peaks of the symmetric and asymmetric complexes, compared to the above mentioned ligand, suggested that the polarizability of the side groups is considerably reduced. This result enhances the proposed complexation mode of the ligand through oxygen next to carbons 3 and 4 of the 5-member ring. 相似文献
17.
Wang Guangbin 《光谱学快报》2013,46(4):679-688
Some new metal complexes of two dipeptide Schiff bases derived from salicylaldehyde and dipeptides such as glycyl-DL-alanine and glycyl-DL-phenylalanine have been synthesized and characterized by elemental analysis, molar conductance, IR, UV spectra, TG and DTA studies. The COO stretching bands in IR spectra suggest that the carboxylate acts as a monodentate group when binding with metal. The ligands are coordinated to the central metal as tetradentate ligands. The bonding sites are the carboxylate oxygen, imino nitrogen, amide nitrogen and phenolic oxygen. 相似文献
18.
19.
Joseph C. Sloop David A. Shultz Mithra Beikmohamadi Marcus Benjamin Shepler 《Journal of Physical Organic Chemistry》2012,25(2):101-109
Linear free‐energy relationships for a series of functionalized semiquinone ligands and their MnII‐ and CuIIhydro‐tris(3‐cumenyl‐5‐methylpyrazolyl) borate complexes were examined. Quinone–semiquinone cycle half‐wave reduction potentials and semiquinone hydrogen hyperfine coupling constants (aH) were determined and their correlation with Hammett σ parameters reported. A new σ parameter, σaH, has been proposed. MnII and CuII metal complex metal–ligand charge transfer and n → π* UV transitions were found to be modulated by substituents. Satisfactory Hammett correlations between UV transitions and various σ values have been determined and compared in a number of instances. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
20.
《Journal of Electron Spectroscopy and Related Phenomena》1988,46(2):315-324
XPS data for a series of octahedral copper(II) diamine tetrafluoroborate and perchlorate complexes are interpreted in the following terms; (i) the inductive effect of diamine substituents; (ii) the degree of cation-anion interaction; (iii) the effect of progressive increase in diamine chelate ring size; and (iv) the Jahn-Teller effect in these complexes. 相似文献