Recep Tapramaz

EPR study of gamma irradiated arsanilic acid single crystal

Abstract EPR spectra of gamma irradiated arsanilic acid single crystal shows rarely observed and unstable arsenate centred [(OH) 2 As=O] radical. There are two magnetically distinct sites in monoclinic lattice. The principal hyperfine and g values of both sites are determined from spectra taking the large hyperfine effects into account. The principal hyperfine values are found to be A x =602, A y =437 and A z =428 Gauss for one site and A x =602, A y =438 and A z =429 Gauss for the other site. The g values of both sites are the same with the values g x =2.048, g y =2.001 and g =2.000. The radical is in slightly distorted C 3v symmetry. The unpaired electron is mainly localised on s orbitals of O atoms and partly on p orbital of central As atom. Calculations of EPR parameters for large hyperfine values are discussed and some easily applicable numerical techniques are utilised.

An EPR Study of Cu2+ Doped Sodium Hydrogen Oxalate Monohydrate Single Crystal

Abstract The EPR spectra of Cu2+ in Sodium hydrogen oxalate monohydrate, NaHC2O4.H2O(SHOMH hereafter) single crystal was studied at room temperature. The angular variation of EPR spectra showed that the Cu2+ ion in SHOMH single crystal substitutes with Na+ monovalent cation together with a monovalent vacancy to compensate oxygen in the crystal. Since the crystal symmetry is triclinic, only one site is observed in the EPR spectra in three perpendicular axis. The spin Hamiltonian parameters were obtained, and the ground state wave function of Cu2+ ion in the lattice was constructed.

EPR and optical-absorption studies of Cu2+-doped Zn(NH2(CH2)3NHOH)2Ni(CN)4 single crystals

Electron paramagnetic resonance of Cu2+-doped catena-trans-bis(N-(2-hydroxyethyl)-ethylenediamine) zinc(II)-tetra-μ-cyanonicelate(II) [Zn(NH2(CH2)3NHOH)2Ni(CN)4] single crystals and powder are examined at room temperature. The spectra show the substitution of the Zn2+ ion with the Cu2+ ion. The crystal field around the Cu2+ ion is nearly axial. There is a single paramagnetic site withgxx=2.073,gyy=2.060,gzz=2.248,Axx=40.5 G,Ayy=50.8 G,Azz=172.0 G. The ground-state wave function is an admixture of dx2−y2 and dz2 states. The optical-absorption studies show two bands at 320 nm (31250 cm−1) and 614 nm (16286 cm−1) which confirm the axial symmetry. The crystal field parameters and the wave function are determined.

EPR studies of gamma-irradiated taurine single crystals

Abstract An EPR study of gamma-irradiated taurine [C 2 H 7 NO 3 S] single crystal was carried out at room temperature. The EPR spectra were recorded in the three at mutually perpendicular planes. There are two magnetically distinct sites in monoclinic lattice. The principle values of g and hyperfine constants for both sites were calculated. The results have indicated the presence of 32 ṠO − 2 and 33 ṠO − 2 radicals. The hyperfine values of 33 ṠO − 2 radical were used to obtain O–S–O bond angle for both sites.

Synthesis, crystal structure, spectroscopic, fluorescent, thermal properties and EPR spectra of doped Cu2+ ions in [Cd(sac)2(H2O)2(meim)2] single crystal

The crystal structures of the six-coordinate complexes [Cd(sac)2(H2O)2(meim)2] (complex 1) formed by reaction of 4-methylimidazole(meim) with [Cd(sac)2(H2O)4]·2H2O (saccharinate=sac), was synthesized and characterized by elemental analysis, infrared (IR) and electron paramagnetic resonance (EPR) spectroscopy, thermal analysis and X-ray single crystal diffraction. X-ray diffraction analysis revealed that complex 1 crystallized in the monoclinic crystal system with space group P21/c. The Cd(II) center was six-coordinated with four nitrogen atoms from two sac and two 4-meim ligands, two oxygen atoms from two aqua ligands. Spectral and thermal analysis data for complex 1 was in agreement with the crystal structures. In addition complex 1 displayed blue fluorescent emission in the solid state at room temperature. Single crystal EPR spectra at room temperature are resolved and have exhibited that two different Cu(2+) complexes were located in different chemical environments which contained two magnetically nonequivalent Cu(2+) sites. In low temperature EPR spectra down to 110 °C did show no considerable change. At higher temperatures, however, both thermo gravimetric analyses (TGA) and EPR spectra showed detectable changes around 140 °C; the causes and the mechanisms of changes are discussed.

Thermal and EPR spectroscopic studies of novel coordination compound trans-bis(acesulfamato)tetraaquazinc(II) with Mn(II) impurity

The thermogravimetric analysis (TGA) and electron paramagnetic resonance (EPR) studies of powder and single crystals of bis(acesulfamato)tetraaquazinc(II), Zn(acs)(2)(H(2)O)(4), a novel coordination compound, are carried out. Previously synthesized bis(acesulfamato) tetraaquamanganese(II), Mn(acs)(2)(H(2)O)(4), is included into the host in trace amount as a paramagnetic probe for EPR analysis. Single crystal EPR spectra at room temperature are resolved and discussed. Low temperature EPR spectra down to 90K do not show remarkable change. At higher temperatures, however, the TGA and EPR spectra show changes around 335 K and 395 K; the causes and the mechanisms of changes are discussed.

EPR study of a gamma-irradiated (2-hydroxyethyl)triphenylphosphonium chloride single crystal

In this study, gamma-irradiated single crystals of (2-hydroxyethyl)triphenylphosphonium chloride [CH2CH2OH P(C6H5)3Cl] were investigated with electron paramagnetic resonance (EPR) spectroscopy at room temperature for different orientations in the magnetic field. The single crystals were irradiated with a 60Co-γ-ray source at 0.818 kGy/h for about 36 h. Taking the chemical structure and the experimental spectra of the irradiated single crystal of the title compound into consideration, a paramagnetic species was produced with the unpaired electron delocalized around 31P and several 1H nuclei. The anisotropic hyperfine values due to the 31P nucleus, slightly anisotropic hyperfine values due to the 1H nuclei and the g-tensor of the radical were measured from the spectra. Depending on the molecular structure and measured parameters, three possible radicals were modeled using the B3LYP/6-31+G(d) level of density-functional theory, and EPR parameters were calculated for modeled radicals using the B3LYP/TZVP method/basis set combination. The calculated hyperfine coupling constants were found to be in good agreement with the observed EPR parameters. The experimental and theoretically simulated spectra for each of the three crystallographic axes were well matched with one of the modeled radicals (discussed in the text). We thus identified the radical C˙H2CH2 P(C 6H5)3 Cl as a paramagnetic species produced in a single crystal of the title compound in two magnetically distinct sites. The experimental g-factor and hyperfine coupling constants of the radical were found to be anisotropic, with the isotropic values g iso = 2.0032, G, G, G and G for site 1 and g iso=2.0031, G, G G and G for site 2.

An EPR study on tea: Identification of paramagnetic species, effect of heat and sweeteners

Tea (Camellia Sinensis) is the most widely consumed beverage in the world, and is known to be having therapeutic, antioxidant and nutritional effects. Electron paramagnetic resonance (EPR) spectral studies made on the tea cultivated along the shore of Black Sea, Turkey, show Mn(2+) and Fe(3+) centers in green tea leaves and in black tea extract. Dry black tea flakes and dry extract show additional sharp line attributed to semiquinone radical. The origins of the paramagnetic species in black tea are defined and discussed. Effect of humidity and heat are investigated. It is observed that dry extract of black tea melts at 100 degrees C and the semiquinone radical lives up to 140 degrees C while Mn(2+) sextet disappears just above 100 degrees C in tea extract. Natural and synthetics sweeteners have different effects on the paramagnetic centers. White sugar (sucrose) quenches the Mn(2+) and semiquinone lines in black tea EPR spectrum, and glucose, fructose, lactose and maltose quench Fe(3+) line while synthetic sweeteners acesulfam potassium, aspartame and sodium saccharine do not have any effect on paramagnetic species in tea.

ESR of Gamma Irradiated C2H204.2H2O Single Crystal

Abstract The gamma-irradiated samples of vacuumed powder and single crystal of C2H2O4.2H2O have been investigated by ESR method. the spectra of these single crystal and unvacuumed powder are attributed to R C HOH radical, but the peaks belonging to this radical in the gamma irradiated powder sample are not observed in the spectrum after having been vacuumed. After a and g tensor values of this radical have been calculated, it was observed to be anisotropic. At low temperature, a considerable change in the spectrum has not been observed.

ELECTRON SPIN RESONANCE STUDIES OF THE RADICALS OF (Ar′O)2P(S)Cl AND (Ar″O)3P=S INDUCED BY GAMMA IRRADIATION (Ar′=2,6-DIMETHYLPHENYL AND 2-TERT-BUTYLPHENYL Ar″=2-ISO-PROPYL-5-METHYLPHENYL)

Abstract A newly synthesized and dedected stable thiophosphorylradicals, bis(2,6-dimethylphenoxy)thiophosphoryl and bis(2-tert-butylphenoxy)thiophosphosphoryl and alkyl radical have been observed in gamma irradiated bis(2,6-dimethylphenyl)chlorothiophosphate and bis(2-tert- butylphenyl)chlorothiophosphate and tris(2-iso-propyl-5-ethylphenyl)thiophosphate single crystals respectively. The characteristic feature is that the phosphorus hyperfine splitting are 26.76 G and 26.65 G respectively for two compounds, but the g values are very unisotropic varying between 1.9996 and 2.054. Tris(2-iso-propyl-5-methylphenyl)thiophosphate does not give phosphoryl radical on gamma irradiation. The radical observed is carbon-centered (alkyl) and forms after 1,6-hydrogen shift on isopropyl group towards sulphur atom giving methyl proton splitting with 15.86 G and a proton siplitting in the neighborhood with 5.5 G. The g value is measured to be 2.0025 for this radical.