Esat Bozkurt

Structural characterization and EPR spectral studies on mononuclear copper(II) complex of saccharin with ethylnicotinate

Mononuclear copper(II) saccharinate (sac) complex containing ethylnicotinate (enc), [Cu(enc)(2)(sac)(2)(H(2)O)].1.4H(2)O has been synthesized and characterized by spectroscopic (IR, UV-vis, EPR), X-ray diffraction technique and electrochemical methods. It crystallizes in the tetragonal crystal systems with space group I4(1)cd and Z=8. The copper(II) ion presents a CuN(4)O distorted square pyramidal coordination. Based on EPR and optical absorption studies, spin-Hamiltonian and bonding parameters have been calculated. The g-values, calculated for title complex in polycrystalline state at 298 K and in frozen DMF (110K), indicate the presence of the unpaired electron in the d(x)(2)-(y)(2) orbital. The evaluated metal-ligand bonding parameters showed strong in-plane sigma and in-plane pi-bonding. Some comparisons with related structures are made and the most important features of its IR spectrum were also discussed. The cyclic voltammogram of the title complex investigated in DMF (dimethylformamide) solution exhibits only metal centred electroactivity in the potential range +/-1.25 V vs. Ag/AgCl reference electrode.

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.

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, characterization, EPR, electrochemical, and in situ spectroelectrochemical studies of salen-type oxovanadium(IV) and copper(II) complexes derived from 3,4-diaminobenzophenone

A new half unit and some new symmetrical or asymmetrical VO(IV) and Cu(II) complexes of tetradentate ONNO Schiff base ligands were synthesized. The probable structures of the complexes have been proposed on the basis of elemental analyses and spectral (IR, UV–Vis, electron paramagnetic resonance, ESI-MS) data. VO(IV) and Cu(II) complexes exhibit square pyramidal and square-planar geometries, respectively. The complexes are non-electrolytes in dimethylformamide (DMF) and dimethylsulfoxide. Electrochemical behaviors of the complexes were studied using cyclic voltammetry and square wave voltammetry. Half-wave potentials (E 1/2) are significantly influenced by the central metal and slightly influenced by the nature of substituents on salen. While VO(IV) complexes give VOIV/VOV redox couples and a ligand-based reduction process, Cu(II) complexes give only a ligand-based reduction. In situ spectroelectrochemical studies were employed to determine the spectra of electrogenerated species of the complexes and to assign the redox processes. The g-values were calculated for all these complexes in polycrystalline state at 298 K and in frozen DMF (113 K). The evaluated metal–ligand bonding parameters showed strong in-plane σ-bonding for some Cu(II) complexes.

An EPR study of Cu2+ doped diaquabis(nicotinamide)bis(o-sulfobenzimidato-N)-cadmium(II) single crystals.

The electron paramagnetic resonance spectra of Cu(2+) doped diaquabis(nicotinamide)bis(o-sulfobenzimidato-N)-cadmium(II) (hereafter, CdNAS) single crystals which were taken at room temperature are discussed. It was found from the analysis of the EPR data that the Cu(2+) ions substitute for magnetically inequivalent Cd(2+) ions. Two magnetically inequivalent Cu(2+)sites were observed. The principal values of the g and the hyperfine tensors were determined. The ground state wave functions of the unpaired electron of Cu(2+) ions in two sites were constructed and type of the distortion was determined.

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.

Synthesis, crystal structure, EPR spectra of Cu2+ doped [Zn(methylisonicotinate)2(H2O)4]·(sac)2 single crystal.

The tetraaquabis(methylisonicotinate)zinc(II) disaccharinate [hereafter, [Zn(mein)2(H2O)4]·(sac)2], complex has been synthesized and characterized by spectroscopic IR, EPR and X-ray diffraction technique. The octahedral Zn(II) ion, which rides on a crystallographic centre of symmetry, is coordinated by two monodentate mein ligands through the ring nitrogen and four aqua ligands to form discrete [Zn(mein)2(H2O)4] unit, which captures two saccharinate ions in up and down positions, each through intermolecular hydrogen bonds. The magnetic environments of Cu2+ doped [Zn(mein)2(H2O)4]·(sac)2 complex have been identified by electron paramagnetic resonance (EPR) technique. EPR spectra of Cu2+ doped [Zn(mein)2(H2O)4]·(sac)2 single crystals have been studied between 113 and 300 K in three mutually perpendicular planes. The calculated results of the Cu2+ doped [Zn(mein)2(H2O)4]·(sac)2 indicate that Cu2+ ion contains two different complexes and each complexes are located in different chemical environments and each environment contains two magnetically inequivalent Cu2+ sites in distinct orientations occupying substitutional positions in the lattice. The vibrational spectra of this compound were discussed in relation to other compounds containing methyl isonicotinate and saccharinate complexes. The assignments of the observed bands were discussed.

EPR Study of VO2+ Doped Diammonium Tricadmium Tetrakis (Sulfate) Pentahydrate [(NH4)2Cd3(SO4)4 ∙ 5H2O] Single Crystals

Electron paramagnetic resonance (EPR) studies are carried out on vanadyl (VO2+) ions in diammonium tricadmium tetrakis (sulfate) pentahydrate single crystals at room temperature. The EPR spectra of a single crystal exhibit resonance signals characteristic to VO2+ ions. The analysis of EPR spectra indicates that the VO2+ ions in single crystals show two magnetically inequivalent VO2+ sites in distinct orientations occupying substitutional positions in the lattice and showing very high angular dependence. They form in octahedral coordination with tetragonal compression with C4v symmetry. The spin Hamiltonian parameters are determined, and these parameters have been used to estimate the bonding coefficients of the VO2+ ion in a diammonium tricadmium tetrakis (sulfate) pentahydrate lattice. The parallel and perpendicular components of axially symmetric g and hyperfine (A) tensors are evaluated and the results are discussed and compared with previous reports.