ESR Spectra Of Cu Research Articles

COMPLEXATION OF METAL IONS WITH 3,5-DI-TERT-BUTYL-1,2-BENZOQUINONE-1-MONOOXIME, ESR STUDIES OF RADICAL INTERMEDIATES

The possibility of chelate formation of 3,5-di-terf-butyl-o-benzoquinone-1-monooxime with Cu(II), Co(II), Ni(II), Mn(II), Pd(II) metal ions under N2 and in air have been investigated. It was found that complexation of metals except Cu(II) and Mn(II) was accompanied by formation of various stable radical species under air. The complexation of Co(II) even under N2 unlike other metal ions, results in the formation of very stable radical species, which are assigned to phenazinyl type radical. ESR examination of reduction of bis(3,5-di-tert-butyl-o-benzoquinone-1-monooximato)M(II) (M = Cu, Pd) with triarylphosphines P(C6H4 X)3 (X = H, m-Cl, m-CH3, p-Et2N) reveal the formation of the N-(2′-hydroxy-3,5-di-tertbutylphenyl)-4′,6′-di-tertbutyl-o-benzosemiquinone iminate radical. Finally, ESR spectra of Cu(II), Ni(II), and Mn(II) complexes at 300 and 130 K, as well as reaction of bis(oximato)Ni(II) with PPh3 have been studied.

Influence of copper concentration on the ESR spectrum of Cu 2+ in MgO

Electron spin resonance spectra of copper-doped magnesium oxide have been studied at room temperature for Cu concentrations between 0.10 and 0.50 mol%. The results suggest that the range of the exchange interaction between Cu 2+ ions is about 0.60 nm.

Syntheses and properties of some transition metal complexes with methyl substituted 1-hydroxy-2(1H)-pyridinethione and crystal structure of bis(1-hydroxy)-4-methyl-2-(1H)-pyridinethionato- O, S′)zinc(II)

Complexes M II( n-Me-PT) 2 [M  Zn, Pd, Ni and Cu; n = 3 or 4 for Zn, n = 3 for other metals; Me-HPT = methyl substituted 1-hydroxy-2(1H)-pyridinethione] were prepared and their magnetic properties, UV, IR and 1H NMR spectra were obtained. Also, the ESR spectrum of Cu II ( n-M-PT) 2 was investigated. The crystal structure of Zn(4-Me-PT) 2 was determined by X-ray diffraction, showing that the zinc atom lies in a nearly square planar coordination environment of two 4-Me-PT ligands in the trans configuration, in which disordered ethanol molecules are stacked in columns along a crystallographic three-fold axis.

L-Band ESR Spectra of Copper(II) Complexes with CuN4 Configurations

L-band ESR spectrometry has been developed for detecting free radicals or paramagnetic metal ions in intact animals or biological samples which contain much water. Several studies by L-band ESR on free radicals have been reported, but few on paramagnetic elements such as copper(II) or iron(III). We measured L-band ESR spectra of Cu(II) for the first time to investigate the coordination structure around the metal ion in aqueous solution. In X- and L-band ESR, both spectral patterns and parameters have been found to reflect the coordination structure of Cu(II)-polyamine complexes depending on the structures such as square-planar, axially coordinate square-planar, tetrahedral and distorted square-planar (Cu(II) ion is displaced from CuN4 plane). In addition, in L-band ESP, the coordination structures of Cu(II) complexes relate with spectral pattern, ESR parameter (LA-value), stability constants and halfwave potentials in terms of the electron density on Cu(II). Thus, L-band ESR spectrometry was indicated to be useful to know the coordination structure of Cu(II) proteins or enzymes in aqueous solution.

Copper(II) and Cobalt(II) Complexes with Derivatives of Salen and Tetrahydrosalen: An Electron Spin Resonance, Magnetic Susceptibility, and Quantum Chemical Study

2,3-diamino-2,3-dimethylbutane; H2[I&]L1 = N,N-bis(2-hydroxy-3-tert-butyl-5-methylbenzyl)-2,3-diamino2,3-dimethylbutane; H2L2 = N,~-bis(3-tert-butyl-5-chlorosalicylidene)-2,3-di~no-2,3-dimethylbutane; H2[H4]L2 = N,~-bis(2-hydroxy-3-tert-butyl-5-chlorobenzyl)-2,3-diamino-2,3-dimethylbutane). The ESR spectra of Cu(I1) complexes in frozen (100 K) toluene solution exhibit a well-resolved perpendicular part. In addition to hyperfine structure, superhyperfine lines are also seen. The superhyperfine structure in the perpendicular region for both CuL' and CuL2 complexes could be well accounted for by the interaction of two equivalent protons along with the two nitrogen nuclei. The protons here belong to the carbon atoms adjacent to the nitrogen nuclei. In the presence of pyridine (5% v/v) there is a considerable shift in both gll and gL values. The higher gll values compared with those of the parent complexes are consistent with the square pyramidal geometry implying axial (py) coordination. An almost negligible effect of an electronwithdrawing substituent (X5 = C1) on spin Hamiltonian parameters was observed. Due to the aggregation of molecules, no resolved spectrum could be obtained from frozen toluene solutions of both CoL' and CoL2 complexes. The addition of an axial pyridine leads to a better resolution of the spectra. In the presence of dioxygen and pyridine (5% v/v) the frozen (100 K) toluene solution of both CoL' and CoL2 exhibits rhombic symmetry with well-resolved hyperfine structures in all three directions. The shape of the spectra and spin Hamiltonian parameters indicate the interaction of the square pyramidal cobalt core with dioxygen. The interaction of the complexes CoL(py) with molecular oxygen leads to a spin-spin pairing process which results in a partial ligand to metal charge transfer and a large spin density on the oxygen moiety. CoL complexes are low-spin d7 systems with peff = 2.49,~~ for CoL'. The copper complexes CuL and Cu[&]L are magnetically normal = 1.81,~~ for CuL2). The calculated spin densities show that the unpaired electron is localized on the molecular orbital of b2 symmetry which is almost the dv orbital of the central atom. Only negligible spin density appears at the pyridine nitrogen atom, which is in agreement with the ESR measurements. The [CoL'] system exhibits its unpaired electron at the molecular orbital of a1 symmetry which is the net d,z metal orbital. The IND0/2 method yields the description of the dioxygen adduct which matches well with the generally accepted MO model. The QR-INDO/I failed in the prediction of the spin pairing process. It prefers either Co(t). * -02(?4) or Co(4). -02(tt) types of interaction. This may be due to an improper balance of the resonance and exchange contributions to the magnetic coupling.

Structural and dynamic aspects of the paramagnetic Cu(II)methylpyrazole complexes

Abstract The Cu(II)methylpyrazole complexes Cu(3-MP)4SO4, Cu(3-MP)4Cl2 and Cu(3-MP)2ac2 were examined by ESR spectroscopy. The ESR parameters were determined by complete simulation of the solution and powder spectra. The pattern of the ESR spectra of Cu(II) complexes with N-donor ligands in solution is mainly determined by the ratio of the anisotropies of the coupling tensors g and A and the line widths ΔBi = ƒ(mI) for the individual hyperfine transitions. The values of the coupling tensors and the dynamic properties (reorientation times) of the complexes depend in a characteristic manner on the nature and geometric parameters of the N-donor ligands. The existence of the Cu(II)methylpyrazole complexes in solution was proven by the analysis of the 14N-shfs (super hyperfine structure) which indicates the coordination of four molecules of 3-methylpyrazole. The pattern of the powder spectra reflect the pronounced influence of the anions. The largest effect was observed for the Cu(3-MP)2ac2 complex. The acetate anion acts as a bridging ligand and leads to the formation of a dimer with D = 0.077 cm−1 and a Cu2+ ⋯ Cu2+ distance of 347 pm, which is remarkably larger than in Cu(ac)2 · H2O.

Ionic clustering in amine-capped telechelic ionomers from ESR of cupric complexes

ESR spectra of Cu 2+ complexes in amine-terminated telechelic polybutadiene were measured, in order to obtain local information on the bonding in the cupric site. The increase in the line widths with cation content indicates the process of cation clustering. The intercation distances deduced from the broadening of the ESR lines are much shorter than those calculated by assuming of a homogeneous cation distribution and approach the Cu-Cu distance in CuCl 2 .2H 2 O. The results of diamagnetic dilution by Zn 2+ indicate that the cation site is very sensitive to the toatl cation content

Structural studies of metal complexes containing amide ligands

Complexes of Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Pd(II) with di-N-phenyl pyromellitic diimide (PhPMDI) and di-N-pyridyl pyromellitic diimide (PyPMDI) were prepared and characterized based on analytical, molar conductance, magnetic, IR, PMR, electronic and ESR data. Based on analytical and molar conductance, the complexes have been formulated as [M(PhPMDA)(H2O)2]n (M = Mn, Fe, Co, Ni), [Cu(PhPMDA)]n [Pd2(PhPMDA)Cl2(H2O)2], [M(PyPMDA)]n (M = Mn, Fe, Co, Ni and Cu) and [Pd2(PyPMDA)Cl2] In all these complexes PhPMDA acts as a mononegative bidentate ligand whereas PyPMDA acts as a mononegative tridentate one in the form of amide rather than imide. The geometries of the complexes have been proposed based on the electronic spectra. The various bonding parameters have been calculated from the ESR spectra of Cu(II) complexes.

ESR spectra of Cu(II) complexes with biologically important ligands at 77 K

Low-temperature powder ESR studies of Cu(sal) 2·4H 2O, Cu(sal) 2(2-pycar) 2 and Cu(sal) 2(3-pycar) 2 (sal = salicylate ion, pycar = pyridylcarbinol) are reported. Spin-Hamiltonian parameters (obtained from experimental spectra, by the nonlinear optimization method) indicate, that the unpaired electron is in the antibonding ψ b 1g molecular orbital in all complexes, which clearly demonstrates an elongated tetragonal bipyramidal coordination around Cu(II). Spin-Hamiltonian parameters are used to estimate the molecular orbital coefficients for the Cu(sal) 2(2-pycar) 2 and Cu(sal) 2(3-pycar) 2.

Electron spin resonance and optical absorption spectra of Cu 2+ ions in alkali zinc borosulphate glasses

Electron spin resonance and optical absorption spectra of R 2SO 4·B 2O 3·ZnSO 4 (R = Li, Na, K and Cs) glasses containing 1 mol% CuSO 4 have been studied. The ESR spectrum of Cu 2+ ions doped glasses exhibits a pronounced peak at g = 2.043 and a shallow quadruplet at g = 2.426, the latter arising from the splitting of g ∥. The optical absorption spectra of Cu 2+ ion doped glasses show broad absorption bands whose peaks range from ∼800 to 845 nm and which we attribute to a 2 B 1 g → 2 B 2 g transition. By correlating the ESR and optical absorption data, the bonding orbital coefficients α 2 and β 1 2 for Cu 2+ ions have been evaluated.

Electron spin resonance and optical absorption spectra of Cr 3+ and Cu 2+ ions in K 2SO 4ZnSO 4 glasses

ESR and optical absorption of Cr 3+ and Cu 2+ ions doped in K 2SO 4ZnSO 4 glasses have been studied at different temperatures (123 K to 423 K). Changes have been observed in the spectrum with changes in temperature, concentration and composition of the glasses. The low field spectral line of the ESR spectrum of Cr 3+ ions in K 2SO 4ZnSO 4 glasses is attributed to isolated Cr 3+ ions whereas the high field spectral line is assigned to exchange coupled pairs of Cr 3+ ions. ESR spectrum of Cu 2+ ions doped glasses exhibit a pronounced peak at g = 2.06, and a quadruplet at g = 2.41, the latter arising from the hyperfine splitting of g V; . From the optical absorption spectrum of Cr 3+ ions doped glass, the crystal field parameter ( Dq) and the Racah interelectronic repulsion parameters ( B and C) have been evaluated. The optical absorption spectrum of Cu 2+ ion doped glass shows a broad absorption band which is attributed to the 2 B 1 g → 2 B 2 g transition. By correlating the ESR and optical absorption data, the bonding orbital coefficients α 2 and ß 2 1 for Cu 2+ ions have been evaluated.

Synthesis, characterization and antitumor activity of some metal complexes of 3- and 5-substituted salicylaldehyde o-hydroxybenzoylhydrazones

Complexes of Mn(II), Fe(III), Fe(II), Co(II), Ni(II), Cu(II), Zn(II) and Pt(II) with 3- and 5-substituted salicylaldehyde o-hydroxybenzoylhydrazones (XSBH, X = H, 3-NO 2, 3-CH 3O, 5-Cl, 5-Br, 5-CH 3 or 5-NO 2) have been prepared and characterized by elemental analysis, conductance measurements, magnetic susceptibilities (from room temperature down to liquid nitrogen temperature) and spectral studies. These studies indicate the following structures: monomeric, high-spin, distorted octahedral for Mn(XSBH) 2; monomeric, high-spin, five-coordinate for Fe(XSBH)SO 4·H 2O; dimeric, high-spin phenoxide bridged, five-coordinate for Fe(XSBH)Cl; dimeric, high-spin five-coordinate for Co(XSBH)Cl·2H 2O; dimeric low-spin, five-coordinate for Ni(XSBH)Cl·2H 2O; dimeric, four-coordinate for Zn(XSBH); and a square-planar structure for M(XSBH)Cl·H 2O (M = Cu(II) or Pt(II). Intermolecular antiferromagnetic exchange interactions are present in Fe(III) complexes, where the exchange parameter ( J) is ca. −8.0 cm −1 for these complexes. The Fe(III) complexes exhibit asymmetric quadrupole split doublets in their 57Fe Mössbauer spectra. The asymmetry is found to be temperature dependent with relatively symmetrical doublets seen at low temperature. The polycrystalline ESR spectra of Cu(II) complexes are isotropic and indicate a d x 2−y 2 ground state in square-planar stereo-chemistry. All these metal complexes have been screened for their antitumor activity against the P 388 lymphocytic leukaemia test system in mice and enhanced antitumor activity relative to the free ligand was found but no significant activity at the dosages used.

Synthesis, characterization and antitumor properties of some metal complexes of 30and 5-substituted salicylaldehyde 2-pyridinylhydrazones

Complexes of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), and Pt(II) with 3- and 5-substituted salicylaldehyde 2-pyridinylhydrazones (XSPH, X  H, 3-NO 2, 3-CH 3O, 5-Br, 5-Cl, 5-CH 3, or 5-NO 2) have been prepared and characterized by elemental analysis, conductance measurements, magnetic moments (300-78 K), and spectral studies. On the basis of these studies a monomeric, high-spin, distorted octahedral structure for Mn(XSPH) 2 and Fe(XSPH) 2, a dimeric, high-spin, five-coordinate structure for Co(XSBH)Cl, a dimeric, low-spin, five-coordinate structure for Ni(XSPH)Cl and Zn(XSPH)(OAc), and a square-planar structure for M(XSPH)Cl· H 2O (M  Cu(II) or Pt(II)) complexes are suggested. The polycrystalline ESR spectra of Cu(II) complexes are isotropic and suggest d x 2−y 2 ground state in squareplanar stereochemistry. Mössbauer spectral results indicate distorted octahedral structure for iron(II) complexes. All the metal(II) complexes have been screened for their antitumor activity against P388 lymphocytic leukemia test system in mice and have been found to possess no significant activity at the dosages used.

Synthesis, characterization and antitumor activity of manganese(II), cobalt(II), nickel(II), copper(II), zinc(II) and platinum(II) complexes of 3- and 5-substituted salicylaldehyde benzoylhydrazones

Complexes of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Pt(II) with 3- and 5-substituted salicylaldehyde benzoylhydrazones (XSBH, X = H, 3-NO 2, 3-CH 3O, 5-Br, 5-Cl, 5-CH 3 or 5-NO 2) were prepared and characterized by elemental analyses, conductance measurements, magnetic moments (300−78 K) and spectral studies. On the basis of these studies the following structures are suggested: distorted octahedral for Mn(XSBH) 2, dimeric, low-spin, five- coordinate for Ni(XSBH)Cl·2H 2O, dimeric, high-spin, five-coordinate for Co(XSBH)Cl·2H 2O, dimeric four- coordinate for Zn(XSBH) and a square-planar structure for M(XSBH)Cl·H 2O (M = Cu(II) or Pt(II)). The polycrystalline ESR spectra of Cu(II) complexes are isotropic and indicate a d x2− y2 ground state in square-planar stereochemistry. All the metal(II) complexes were screened for their antitumor activity against the P388 lymphocytic leukaemia test system in mice and were found to possess no significant activity at the dosages used.

Stereochemistry and structural phase transition of Cu(II) complexes containing orthophosphate ions and pyridine/picoline

Copper complexes of the type Cu(L)4(H2PO4)2 designated as complex (I), and Cu(L)4 HPO4 designated as complex (II), (whereL = pyridine (py) or λ-picoline (pic)) have been synthesised, characterised by chemical analyses, IR, and electronic and magnetic susceptibility data. From ESR studies it is concluded that complexes (I) have elongatedtrans octahedral stereochemistry. The temperature dependence of the ESR spectrum of Cu(py)4(H2PO4)2 suggests a fluxional behaviour in the immediate coordination of Cu(II), whereas very little variation of the ESR spectrum of the Cu(pic)4(H2PO4)2 complex indicates that the stereochemistry of this complex is essentially static in nature. The differential scanning calorimetric studies in the case of Cu(py)4(H2PO4)2 complex have given clear evidence for the occurrence of a structural phase transition at 147 K. The absence of any abrupt changes in the ESR spectrum at that temperature excludes the possibility of any changes in the immediate environment of Cu(II).

Magnetic and spectral studies on 3d-metal complexes of acetone(N-isopropylidene)tyrosyl hydrazone

Acetone(N-isopropylidene)tyrosyl hydrazone, HO-C6H4-CH2-CH(N=CMe2)-CONHN=CMe2 (ath), has been found to form adducts of the typeM (ath) Cl2·nH2O [M = Mn (II), Co (II), Ni (II), Cu (II) and Zn (II);n = 0, 1 or 2] and deprotonated complexes of the type M′(ath-2H) · 3H2O[M′ = Co(II), Ni(II) and Cu(II)]. Molar conductance studies in 0.001 Mdmso solution have indicated the non-ionic nature of the complexes. High-spin octahedral geometry for Mn(II) and Ni(II) complexes and tetrahedral geometry for Co(II) adduct have been proposed on the basis of magnetic and/or electronic spectral studies.ir spectra suggest neutral bidentate and dinegative tridentate behaviour of the ligand in the adducts and deprotonated complexes respectively,esr spectra of Cu(II) complexes indicate zero-field splitting of Cu(ath)C12 · H2O and metal-metal interaction in both the complexes.

Synthesis and Structural Studies of Some First Row Transition Metal Complexes of N-Benzoylglycine Hydrazide

Abstract N-Benzoylglycine hydrazide(BzGH) has been found to react with bivalent 3d-metal ions forming complexes of the types M(BzGH)2Cl2, M'(BzGH-H)2·nH2O and M' (BzGH-2H)·3H2O [M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II); M' = Co(II), Ni(II) and Cu(II); n = 1 or 2]. Molar conductance studies in 0.001 M DMSO solutions have indicated the non-ionic nature of the complexes. High-spin octahedral geometry for Mn(II), Co(II) and Ni(II) complexes has been suggested on the basis of magnetic and/or electronic spectral studies. IR spectra suggest neutral bidentate, uninegative bidentate and dinegative tridentate behaviour of the ligand in the complexes. ESR spectra of Cu(II) complexes indicate a dx2-y2 ground state of the metal atom with a very weak metal-metal interaction in Cu(BzGH-H)2·H2O and Cu(BzGH-2H)·3 H2O.

Synthesis and spectral studies of copper(II) complexes with amide group ligands

Complexes of copper(II) with 2-(acetylamino)benzoic acid, 2-(benzoylamino) benzoic acid, 2-(aminocarbonyl)benzoic acid, 2-[(phenylamino)carbonyl]benzoic acid, 2-[(1-naphthalenylamino)carbonyl]benzoic acid, 2-[(2-aminophenylamino)carbonyl]benzoic acid, 2-aminobenzanilide, 2(aminobenzoyl)benzoic acid, maleanilic acid and malea-1-naphthalanilic acid have been prepared and characterized by chemical analyses, molar conductivity, magnetic susceptibility measurements, thermal data, IR, electronic and ESR spectra. The visible and ESR spectral studies of these complexes (except those of maleanilic acid and malea-1-naphthalanilic acid) indicate that they are monomeric having either square planar or distorted octahedral geometry around Cu(II). The Cu(II) complexes of maleanilic acid and malea-1-naphthalanilic acid have been tentatively assigned dimeric structures. From the ESR spectra of Cu(II) complexes various parameters have been calculated.

Electron spin resonance spectra of chloro(N-methyl-5,10,15,20-tetraphenyl-porphinato)copper(II) and manganese(II) complexes. Demethylation mechanism studies

ESR spectra of Cu(II) and Mn(II) complexes of N-methyl-5,10,15,20-tetraphenylporphyrin (NCH3TPPH) were studied. A large influence of the pyrrole nitrogen methylation on ESR parameters of Cu(NCH3TPP)Cl and Mn(NCH3TPP)Cl as compared to Cu(TPP) or Mn(TPP) was observed and discussed.The five-coordinate forms of formula Mn(NCH3TPP)X, where X = Cl− or solvent molecule, were defined by characteristic g⊥eff values. The rhombic ESR Hamiltonian (D ≠ 0, E ≠ 0) was accounted for the observed ESR spectra of the five-coordinate forms contrary to the axial one (D ≠ 0, E = 0) for Mn(TPP). Spontaneous demethylation of the Cu(NCH3TPP)Cl complex and formation of Cu(TPP) was observed on the basis of ESR spectra. The decomposition of Mn(NCH3TPP)Cl in the presence of di-n-butylamine (DBA) was analysed. The ESR experimental evidence was found for the presence of Mn(TPP)DBA and Mn(TPP)O2 species as intermediates of this process.

Structure dependence of ESR spectra of Cu(II) complexes of aliphatic and trytophan containing dipeptides and ATP

Spectra and stability constants of binary and ternary complexes were derived from ESR spectra of aqueous solutions of Cu(2+), ATP and the dipeptides gly-L-trp and L-trp-gly. The stability of binary as well as ternary complexes is only slightly influenced by the tryptophan side chain. Parameters affecting the shape of an ESR spectum of a Cu(II) complex in solution are discussed in detail. A comparison of the ESR spectra of the several complex species reveals the different influence of electronic and mobility contributions of the tryptophan side chain depending on the position of tryptophan in the dipeptide. In ternary complexes, the spectral shape is determined by the stronger binding ligand.