Ibrahim Kartal

EPR studies of Cu2+-doped bis(saccharinato)bis(pyridine)zinc(II) single crystals

The electron paramagnetic resonance spectra of Cu2+ impurities in bis(saccharinato)bis(pyridine)zinc(II) single crystals have been studied at room temperature in three mutually perpendicular planes. The angular variation of the spectra indicates the substitution of the host Zn2+ with Cu2+. Two magnetically inequivalent sites for Cu2+ have been observed. The spectra were fitted to the rhombic spin Hamiltonian. The spin Hamiltonian parameters and the molecular orbital coefficients were evaluated for the two sites. The ground-state wave function of Cu2+ ion in the lattice has been constructed.

Electron paramagnetic resonance of Cu2+ in Cd(NH4)2(SO4)2 · 6H2O

Abstract The electron paramagnetic resonance spectra of Cu2+ in Cd(NH4)2(SO4)2 · 6H2O powder and single crystals have been recorded at 300 K and 113 K. The angular variation of the spectra indicated the substitution of the host Cd2+ with Cu2+. Two magnetically inequivalent sites for Cu2+ have been observed. The spectra were fitted with a rhombic spin Hamiltonian and the Hamiltonian parameters were determined. The g and A tensors were found to be coaxial within the limits of experimental errors and the ground state wavefunction of the complex has been constructed.

EPR of gamma irradiated Nα-acetyl L-glutamic acid and Nα-acetyl L-glutamine

Abstract Single crystals of Nα-acetyl L-glutamic acid and Nα-acetyl L-glutamine were γ-irradiated and the paramagnetic species formed were investigated at room temperature by electron spin resonance technique. The observed species in Nα-acetyl L-glutamic acid single crystal were attributed to the, HOOCCH 2 CH 2 C (NHCOCH 3 )COOH radical; and those in Nα-acetyl L-glutamine single crystal to the NH 2 COCH 2 CH 2 C( NHCOCH 3 ) COOH and NH 2 COCH 2 CH 2 CH ( NHCOCH 3 ) C O OH radicals. The g values and the hyperfine coupling constants of the unpaired electron with the environmental methylene, methine protons and 14 N nucleus were determined.

Structural, spectroscopic and EPR studies of tetraethylammonium tetramethylammonium tetrabomocuprate (II) complex

Abstract The tetraethylammonium tetramethylammonium tetrabromocuprate(II), (hereafter, [(TEA)(TMA)CuBr4]) [(C2H5)4N][(CH3)4N][CuBr4], complex was synthesized and characterized by spectroscopic (IR), structural (XRD) and electron paramagnetic resonance (EPR) technique. The compound contains four isolated and discrete moieties, i.e. two independent [(CH3)4N]+ cations, with one on a -4 axis and the other with the central N atom on a 2z axis, one [(C2H5)4N]]+ cation, on a mirror plane and in a trans conformation, and one distorted tetrahedral [CuBr4]2– anion on another mirror plane. The electron paramagnetic resonance spectra of [(TEA)(TMA)CuBr4] single crystals and powder were investigated in the temperature range from 300 to 5 K. The observed values from the line width and g tensors were found to be temperature dependent. The temperature dependence of Cu(II) complex with EPR spectra values were also discussed in terms of dynamic Jahn-Teller effect.

EPR study of Cu2+-doped tetraaqua-di(nicotinamide)Co(II) saccharinate single crystals

The electron paramagnetic resonance spectra of Cu(2+) impurities in [Co(nicotinamide)(2)(H(2)O)(4)](saccharinate)(2) single crystals have been studied at ambient temperature in three mutually perpendicular planes. The angular variation of the spectra shows that the Cu(2+) ion substitutes the Co(2+) site in the lattice. The EPR spectra of Cu(2+) ions are characteristic of tetragonally elongated octahedral site. The spin-Hamiltonien parameters were obtained from the single crystal EPR analysis. The ground-state wave function of Cu(2+) ion in the lattice has been constructed.

Synthesis and ESR studies of redox reactivity of bis (3,5-di-tert-butyl-1,2-benzoquinone-2-monooximato)Cu(II)

Complexing of 3,5-di-tert-butyl-1,2-benzoquinone-2-monooxime with Cu(II) in air and under N2 gave Cu(qo)2 and Cu(qo)2 x H2O (where qo is 3,5-di-tert-butyl-1,2-benzoquinone-2-monooximato-anion) complexes, respectively. The ESR spectroscopy showed that the reduction of these complexes with P(PhX)3 (X = H, m-Cl, m-CH3, p-Et2N-) and 1,4-bis(diphenyldiphosphino) butane (dppb) proceeds via the radical formation (phenoxazine, amino phenoxy and nitrene type radical intermediates) and pathways of reduction depend on the structure of these complexes. The reaction of Cu(qo), with dppb and P(PhX)3 phosphines gave essentially identical ESR spectra. At the same time, reduction of Cu(qo)2 x H2O with PPh3 result in entirely different unstable radical spectrum (g = 2.0046) which is further converted to another relatively stable Cu-containing radical signal (g = 2.0052). The unstable radical species attributed to nitrene type radicals. The initial complexes and all radical products were characterized by their ESR and optical spectra.

Synthesis, Spectroscopic Characterization and Redox Reactivity of Some New N-(2,6-Di-Tert-Butyl-L-Hydroxyphenyl) Salicylaldimines

Abstract New substituted N- (2,6-Di-tert-butyl-l-hydroxyphenyl) Salicylaldimines (LxH) were prepared by the condensation of various hydroxy and methoxy salicylaldehyde derivatives and 2,6-Di-tert-butyl-4-aminophenol and characterized by elemental analysis, IR, UV-Vis, 1H NMR spectroscopy, as well as ESR studies of the oxidation products of LxH. It was found that LxH, unlike analogous electron-withdrawing C1, Br, NO2 bearing derivatives, in the solid state exist both in associated and non-associated forms. UV-Vis and 1H, NMR studies show that LxH in solutions exists both in phenolimine and ketoamine tautomer forms. In addition, alcohol solutions of LxH exhibited a new band in the region of 630-675 run. The ESR studies of one -electron oxidation of LxH, in the condition of THF, CHC13 and toluene solutions at 300 K, indicate the formation of corresponding primary or secondary phenoxyl radicals. It was found that the stability and conversion pathway of the primary phenoxyl radicals are dependent upon both kin...

EPR studies of VO2+ doped bis(saccharinato)bis(pyridine) zinc (II) single crystals

Electron paramagnetic resonance (EPR) studies of vanadyl ions, VO2+, as paramagnetic impurity in bis(saccharinato)bis(pyridine)zinc (II) [hereafter, Zn(sac)2(py)2] are made at room temperature. The angular variation of the EPR spectra has shown that three different VO2+ complexes are located in different chemical environments and each environment contains two magnetically inequivalent VO2+ sites in distinct orientations occupying substitutional positions in the lattice and show very high angular dependence. The spin-Hamiltonian parameters are determined and these parameters have been used to assess the bonding coefficients of the VO2+ ion in [Zn(sac)2(py)2] lattice. The values of spin-Hamiltonian parameters indicate that the VO2+ ions in [Zn(sac)2(py)2] were present in octahedral coordination with a tetragonal compression and belong to C4v symmetry. The parallel and perpendicular components of axially symmetric g and hyperfine tensors are evaluated and the results are discussed.

Bis[N-(2,6-di-t-butyl-1-hydroxyphenyl)salicylideneaminato]palladium(II) complexes and their radical intermediates generated by PbO2 and PPh3

New bis[N-(2,6-di-t-butyl-1-hydroxyphenyl)salicylideneminato]palladium(II) [Pd(Lx)2] complexes bearing HO and MeO substituents on the salicyaldehyde moiety were prepared, and their spectroscopic properties, as well as redox reactivity towards PbO2 and PPh3, examined by e.s.r. and u.v. spectroscopy. The complexes display charge-transfer bands in the 670–692 nm range in polar solvents, which are assigned to the d(Pd) → π* (chelated quinoid) transition. One-electron oxidation of Pd(Lx)2 produces PdII-stabilized radicals in which the unpaired electrons are localized on the phenoxy fragments and do not couple with the two radical centers. The complexes are easily reduced with PPh3via intramolecular electron-transfer from ligand to metal to give various radical intermediates and Pd. All detected radical species have been characterized by e.s.r. spectroscopy.

EPR of gamma irradiated (CH3)3NHClO4, (CH3)3NHBF4 and [(CH3)4N]2ZnCl4 single crystals

Abstract Gamma irradiation damage centres in (CH 3 ) 3 NHClO 4 , (CH 3 ) 3 NHBF 4 and [(CH 3 ) 4 N] 2 ZnCl 4 were investigated by electron paramagnetic resonance spectroscopy at room temperature. The centres were found to be (CH 3 ) 3 N +. and the hyperfine structure parameters for methyl protons and the nitrogen nucleus were determined. The results indicated that the (CH 3 ) 3 N +. radical wholly performs reorientational motions around its C 3v axis in addition to the reorientatonal motions of the methyl groups around their C 3v axes. These results were compared with the earlier studies on (CH 3 ) 3 N +. radical and discussed. Low temperature measurements on the first two of the title compounds were assessed.