ESR study of some Cu(II)-4-substituted-2-Thiazolylhydrazone complexes

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 (L_II) were prepared and investigated by ESR measurements. The powder ESR spectrum at room temperature of CuL_IICl is quasi-isotropic (g=2.113), while for CuL_IICl 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.     

ESR study of some solvent effects of the Cu(II)-aspirinate complex

Powder ESR spectra of the [Cu₂(Asp)₄](H₂O)₂ complex show the existence of Cu(II) acetate like dimers characterized by a strong antiferromagnetic exchange interaction (J=?288 cm^?1). In pyridine-dimethylformamide solutions the monomeric species prevail. Two different monomeric species, the Cu(DMF)₄ of planar-distorted tetrahedral (T_d) symmetry and the Cu(Asp)₂(DMF)₂ with elongated tetrahedral-octahedral symmetry were evidenced in DMF solution adsorbed on NaY zeolite. In 40 % Py+60 % DMF solution two monomeric species were also identified. These are Cu(Asp)₂(DMF)₂ and Cu(Asp)₂(Py)₂, the last species having a CuN₂O₂ chromophore in atrans squareplanar arrangement. In pyridine Cu(II)-aspirinate solution only the Cu(Py)₄ monomeric species of CuN₄ chromophore was evidenced.     

ESR study of some asymmetric-triazine copper(II) complexes having high antiviral activity

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.     

Study of Cu K-edge in some copper (II) square planar complexes

The copper K-absorption edge in the complexes Cu(ammonia)₂ C₂O₄, Cu(methylamine)₂ C₂O₄, Cu(ethylamine)₂ C₂O₄ and Cu(aniline)₂ C₂O₄ has been investigated using the Cauchois-type bent crystal X-ray spectrograph. Three peaks, A, B and C, observed in the edges have been explained on the basis of molecular orbital theory.     

ESR of Cu doped cadmium (II) formate dihydrate

Electron spin resonance (ESR) of Cu²⁺ doped cadmium formate dihydrate single crystal was studied at room temperature. Copper enters the lattice substitutionally and is trapped at two magnetically inequivalent sites. The observed spectra are fitted to a spin-Hamiltonian of rhombic symmetry with the following values of the spin-Hamiltonian parameters, Cu²⁺(I): g_x=2.097±0.002, g_y=2.1166±0.002, g_z=2.2887±0.002 and A_x=(140±2)×10⁻⁴ cm⁻¹, A_y=(151±2)×10⁻⁴ cm⁻¹, A_z=(239±2)×10⁻⁴ cm⁻¹, Cu²⁺(II): g_x=2.0843±0.002, g_y=2.1045±0.002, g_z=2.2742±0.002 and A_x=(141±2)×10⁻⁴ cm⁻¹, A_y=(158±2)×10⁻⁴ cm⁻¹, A_z=(267±2)×10⁻⁴ cm⁻¹. The ground state wave function of the Cu²⁺ ion in this lattice is evaluated. It is found that the ground state is predominantly |x²−y²〉. The g-factor anisotropy is also calculated and compared with the experimental value. With the help of the optical absorption study, the nature of bonding in the complex has been discussed.     

ESR study of Cu(II)-indomethacin and its pyridine and DMF adducts

Powder ESR spectra of [Cu₂(Ind)₄](H₂O)₂ at room temperature show the presence of copper acetate like dimers characterized by a strong antiferromagnetic exchange interaction (J≈?338 cm^?1). Two different monomeric species were evidenced in 40%Py+60%DMF solution absorbed on NaY zeolite: the Cu(Ind)₂(DMF)₂ with an elongated tetragonal-octahedral symmetry and the Cu(Ind)₂(Py)₂ with a CuN₂O₂ chromophore in atrans square-planar arrangement. Only one monomeric species Cu(Ind)₂(Py)₂ was identified in 20%Py+80%DMF and 20%Py+80% Chloroform solutions. The Cu(Py)₄ ²⁺ species of CuN₄ chromophore occurs in pyridine Cu(II)-indomethacin solution suggesting a decomposition of the solvit compound.     

ESR investigation of some copper(II)-dioxime-dichloride compounds

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 d_xy ground state was estimated for pseudotetrahedral (Td) species in frozen solutions.     

Liquid-crystalline dendrimer Cu(II) complexes and Cu(0) nanoclusters based on the Cu(II) complexes: An electron paramagnetic resonance investigation

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.     

ESR spectral studies of a Cu(II) salicylidene tyrosine complex

A novel Schiff base derived from salicylidene and tyrosine and its copper(II) complex have been synthesized and characterized. The composition of the complex is K[CuL(Ac)] · H₂O, where L = H₁₃C₁₆NO₄. Electron spin resonance (ESR) spectra of the copper(II) complex were investigated at different temperatures and in various solvents. The second-order effect and the relaxation effect were observed in the solution spectrum at room temperature and satisfactorily explained by the spin Hamiltonian. The bonding parameters of the Cu(II) complex were calculated with spectral parameters from ESR spectra at low temperature. Its bonding characterization and stability were discussed. The result shows that both the in-plane σ-bond and the in-plane π-bond in the complex play an important role.     

An X-ray photoelectron spectroscopic study of some nickel (II) amine complexes

The X-ray photoelectron (XPS) spectra of several Ni(II) diamine complexes, a Ni(II) triamine complex and several Ni(II) diimine complexes are reported in terms of the Ni 2p, Cl 2p and N 1s core level binding energies. Theoretical models are presented to account for the quadratic relationship observed between XPS Ni 2p_{$\text{3}\text{2}$}binding energy shifts and the N-H infrared rocking frequency as related to these complexes. On the basis of this correlation, it is possible to discriminate between free counter-ions coordinated to the metal or involved in cluster-ion formation. Individual XPS data for these complexes are interpreted in terms of the intrinsic nature of the metal environment and an attempt is made to calculate the metal and donor nitrogen atomic charges for selected complexes.     

An X-ray photoelectron spectroscopic study of some bis(diamine)-copper (II) complexes

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.     

Optical spectroscopic study of the Cu(II) complexes with adenosine and adenine nucleotides

Summary Aqueous adenosine-copper and D-ribose copper solutions have been studied as functions ofpH, in thepH range from 3 to 12. Our approach is the study of the effect that the field of ligands produces on the opticald-d transitions of the copper ion. The results show that abovepH 6 the ribose moieties of adenosine bind to the copper ions forming two kinds of soluble 1∶1 complex, one prevailing atpH 9 and the other prevailing atpH 11.5.

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Riassunto La formazione dei complessi del rame con molecole di adenosina e con molecole di D-ribosio in soluzione acquosa è studiata, al variare delpH nell’intervallo da 3 a 12, analizzando l’effetto del campo legante sulle transizioni ottiche tra i livellid dello ione Cu(II). I risultati mostrano che, per valori dipH maggiori di 6, il gruppo ribosio dell’adenosina si lega agli ioni Cu(II) formando due distinti complessi, uno prevalente apH 9 e l’altro prevalente apH 11.5.

     

Anisotropic ESR parameters of Cu(II) complexes in solutions and dynamics of solvent coordination: use of “minimum linewidths”

The “minimum linewidths” seen in the ESR linewidths against temperature plots, the dependence of line widths on the⁶³Cu nuclear magnetic quantum numbers and the Hubbard relation provide sufficient number of equations to determine the anisotropic ESR parameters in the case of axially symmetric Cu(II) complexes even when unresolved hyperfine structures make contributions to linewidths. After testing the method by reanalysing the literature data on Cu(II) bis-acetylacetonate, it has been used to obtain the anisotropic ESR parameters in the case of bis-salicylaldehydate of Cu(II). Linewidth contributions from unresolved hyperfine structures associated with the¹H of coordinating CHCl₃ inferred in these studies, were confirmed by comparing the widths in CHCl₃ and CDCl₃ under ideal conditions. The temperature dependence of this contribution and the estimate of rate constant at room temperature (∼ 10¹⁰ s⁻¹) suggest that the coordinating solvent exchange is diffusion controlled.     

Electrooptical effect in polymeric composites containing heterometallic Cu(II)/Mn(II) complexes

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. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 4, pp. 481–484, July–August, 2007.     

ESCA study of Ni(II) dithiocarbazato complexes

N 1s, S 2p and Ni 2p_3/2 binding energies for the Ni(II) dithiocarbazates and N 1s and S 2p binding energies for the methyl esters of dithiocarbazic acids were measured. It was found that the band width of N 1s narrows on going from the esters to the complexes, thus suggesting a closer similarity between the two nitrogen atoms as a consequence of coordination. S 2p binding energies were found to be similar in the above complexes independent of the chromophore present in them. A possible explanation is suggested for this unusual result.     

Studies on Cu(II), Zn(II), Ni(II) and Co(II) complexes derived from two dipeptide Schiff Bases

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.     

Dielectric studies of a bioactive tetramic acid and its complexes with Cu(II) and Co(II)

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.     

Ni（Ⅱ）,Cu（Ⅱ）,Zn（Ⅱ）的硝酸盐与氟哌酸的固态配合物的 …

由氟哌酸与Ｎｉ（Ⅱ）、Ｃｕ（Ⅱ）、Ｚｎ（Ⅱ）的硝酸盐合成了三个未见报道的固态配合物,并用元素分析、摩尔电导、红外光谱、热重分析表征了它们的组成和性质。