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1.
An amplitude modulation of the electron spin echo envelope has been observed for radiation-produced trapped electrons in 10 M NaOD/D2O at 77°K but not in 10 M N2OH/H2O. The modulation has been simulated theoretically by generalizing the single crystal model of Rowan et al. to disordered systems. The modulation has been interpreted as due to dipolar interactions with deuterons in molecules of the second solvation shell around the trapped electrons. 相似文献
2.
R.S. Rubins 《Chemical physics letters》1974,28(2):273-275
The EPR spectrum of Ni2+ in single crystals of zinc fluotitanate ZnTiF6·6H2O has been studied between 4.2 K and room temperature in the frequency range 14.0–16.5 GHz. A structural transition was observed at (180±2) K between a high-temperature trigonal structure and a low temperature orthorhombic structure. Spin hamiltonian parameters are reported above and below the transition. 相似文献
3.
The EPR spectrum of O− on MgO has been observed following the reaction of N2O with electrons trapped at the surface. The spectrum of the ion in axial symmetry is characterized by g⊥ = 2.041 and g∥ = 2.0016. Upon exposure to H2, CO, CO2 or additional N2O the spectrum is replaced by another having g1 = 2.0172, g2 = 2.0100 and g3 = 2.0014. This spectrum is tentatively assigned to the O3− ion. 相似文献
4.
Martin van Son Jesika T. Schilder Antonella Di Savino Anneloes Blok Prof. Marcellus Ubbink Dr. Martina Huber 《Chemphyschem》2020,21(10):1060-1069
We present a novel approach to study transient protein-protein complexes with standard, 9 GHz, and high-field, 95 GHz, electron paramagnetic resonance (EPR) and paramagnetic NMR at ambient temperatures and in solution. We apply it to the complex of yeast mitochondrial iso-1-cytochrome c (Cc) with cytochrome c peroxidase (CcP) with the spin label [1-oxyl-2,2,5,5-tetramethyl-Δ3-pyrroline-3-methyl)-methanethiosulfonate] attached at position 81 of Cc (SL−Cc). A dissociation constant KD of 20±4×10−6 M (EPR and NMR) and an equal amount of stereo-specific and encounter complex (NMR) are found. The EPR spectrum of the fully bound complex reveals that the encounter complex has a significant population (60 %) that shares important features, such as the Cc-interaction surface, with the stereo-specific complex. 相似文献
5.
Many biologically important paramagnetic metal ions are characterized by electron paramagnetic resonance (EPR) spectroscopy to use as spin probes to investigate the structure and function of biomolecules. Though nickel(II) ions are an essential trace element and part of many biomolecules, the EPR properties are least understood. Herein, the EPR and optical absorption spectra measured at 300 K for Ni(II) ions diluted in two different diamagnetic hosts are investigated and reported. The EPR spectrum of a polycrystalline Ni/Mg(3-methylpyrazole)6(ClO4)2 [Ni/MMPC] shows two transitions at X-band frequency (~9.5 GHz), suggesting the zero-field splitting parameter (D) is larger than the resonance field of the free electron (Ho). This incomplete and complex spectrum is successfully analyzed to obtain EPR parameters. The EPR spectrum of the polycrystalline Ni/Zn(pyrazole)6(NO3)2 [Ni/ZPN] shows a triplet spectrum indicating D < Ho. A detailed analysis of single-crystal EPR data yielded the spin Hamiltonian parameters. The optical absorption spectra are deconvoluted to understand the symmetry of the coordination environment in the complex. 相似文献
6.
D. Dondi A. Buttafava A. Zeffiro R. Cherubini V. De Nadal S. Gerardi A. Faucitano 《Radiation Physics and Chemistry》2012,81(9):1445-1450
The radiation induced free radical damage in Chinese hamster lung fibroblast V-79 cells stored in DMEM culture medium containing 10% DMSO has been investigated by matrix EPR spectroscopy in connection with the H2O/DMSO binary phase diagram. A major part of the indirect effect is due to radicals from the DMSO·3H2O phase in the freezing medium, which are released on warming in the temperature range between 130 K and 160 K, that is, far below the eutectic melting temperature (210 K). The radicals trapped in the DMSO·3H2O phase react with oxygen above 160 K giving reactive oxygen species (ROS) of the type of peroxyl radicals. A lower limit yield of 10–15% was calculated for this conversion. Scavenging experiments with a stable nitroxyl radical (tempol) have demonstrated that part of the DMSO·3H2O radicals escape by mutual recombination on melting and are therefore available for inducing indirect cell damage. The same experiments performed with pure frozen water have shown that OH radicals are not available for inducing cell damage. The EPR measurements performed on H2O/DMSO frozen mixtures suggest that the radiation induced radical forming process does not change when passing to the low dose range below 1 Gy, in agreement with the linear model. 相似文献
7.
Abstract Three complexes of 9-oxo-10-acridinemetanophosphonlc ion (PMA= see figure) have been synthesised. The meta1:ligand ratio in the complexes is equal 1:1 and their formulas are (CUPMA) 2,×5H2O,NiPMA×4H2O and CoPMA×4H2O. The structure of the complexes has been investigated by the IR,FIR, Raman spectroscopy, UV-VIS spectroscopy, magnetic measurements and EPR spectroscopy. The physical properties of the complexes obtained are characteristic for inorganic polymers. The lowering of the ν(P-Q) stretching frequency by about cm?, in the spectra of the complexes as compared to that of the free ligand suggests that the phosphonlc group takes part in coordination. Data from the EPR spectrum indicate that Cu(II)may form the dimeric, water bridged or even more complicated polymeric structures. 相似文献
8.
K.V Narasimhulu J.L Rao 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》1997,53(14):2605-2613
EPR spectra of VO2+ ions doped in single crystals of Cs2Co(SO4)2.6H2O single crystals have been studied at various temperatures (390–103 K) on X-band frequency. The detailed EPR analysis shows three vanadyl complexes with differing intensities. The g and A tensors are found to be axially symmetric. The intense vanadyl complexes in the lattice are found to occupy the Co2+ substitutional sites, whereas the weak vanadyl complex at the interstitial sites. The optical absorption spectrum at room temperature shows three absorption bands characteristic of VO2+ ions in tetragonal symmetry. By correlating the EPR and optical data, the molecular bonding coefficients and the Fermi contact interaction terms have been evaluated and discussed. The line broadening of VO2+ spectra on cooling the crystal is explained on the basis of spin-lattice relaxation narrowing. The spin-lattice relaxation time for the host Co2+ ions has been estimated at various temperatures. 相似文献
9.
Berry JF Bill E Bothe E Cotton FA Dalal NS Ibragimov SA Kaur N Liu CY Murillo CA Nellutla S North JM Villagran D 《Journal of the American Chemical Society》2007,129(5):1393-1401
Reaction of Pd(2)(DAniF)(4), 1, (DAniF = di-p-anisylformamidinate) with 1 equiv of AgPF(6) in CH(2)Cl(2) at or below -10 degrees C produces the paramagnetic species [Pd(2)(DAniF)4]PF(6), 1-PF(6), that has been studied by X-ray crystallography, UV-vis spectroscopy, electrochemistry, and multifrequency (9.5, 34.5, 110, and 220 GHz) EPR spectroscopy. Upon oxidation of the precursor, the Pd-Pd distance decreases by 0.052 Angstrom from 2.6486(8) to 2.597(1) Angstrom. The EPR spectra show broad signals with line widths of about 1000 G. The spectra collected at high field show a large spread of g tensor components ( approximately 0.03), but these are masked at lower frequencies (9.5 and 34.5 GHz). A reinvestigation using high-field EPR of the p-tolyl analogue, which is the only other structurally characterized Pd(2)(5+) species (Cotton, F. A.; Matusz, M.; Poli, R.; Feng, X. J. Am. Chem. Soc. 1988, 110, 1144), shows that this species, which had been reported to give an isotropic 9.5 GHz EPR spectrum, also gives anisotropic 110 and 220 GHz EPR spectra with a similarly large spread of g tensor components consistent with the unpaired electron residing in a metal-based MO. The results of these studies and calculations using density functional theory are consistent with the oxidation being metal-based, resulting in an uncommon Pd(2)(5+) species with a Pd-Pd bond order of 1/2. 相似文献
10.
For the development of extensive investigations into a potential medicinal application of vanadium coordination compounds for the oral treatment of diabetes, new mono and bimetallic VO (IV) complexes with N,N′-(2,2′-(9,10-dihydro-9,10-ethanoanthracene-11,12-dicarbonyl) bis (hydrazine-1-carbonothioyl)) dibenzamide (H6EBT) and 2,2′-((9S,10S,11R,12R)-9,10-dihydro-9,10-ethanoanthracene-11, 12-dicarbonyl) bis (N-phenylhydrazine-1-carboxamide) (H6EPH) have been isolated and characterized. The FTIR and NMR spectral data revealed that H6EBT acts as neutral tridentate and dibasic hexadentate while H6EPH as dibasic tridentate and tetrabasic hexadentate. The electronic and ESR spectra indicated that complexes has octahedral geometry. ESR spectrum of [(VO)(H6EBT)(SO4)].5H2O gives a well resolved hyperfine eight-line pattern typical spectrum for mononuclear vanadyl complexes with g˃ g⊥ = 1.9 suggesting that the ligand donor atoms ONS are coplanar with the two chelate rings forming octahedral geometry. Also, the high parallel hyperfine splitting value, A = 0.0108, than perpendicular one (A⊥ = 0.0087) indicated that the single d- electron is in a σ-nonbonding orbital and aiming away from the equatorial ligands. On the other hand, the EPR spectra of the binuclear [(VO)2(H4EBT)(SO4)]3H2O and [(VO)2(H2EPH)(H2O)2].10H2O complexes gave a single broad line centered at g = 2.05 and 2.07, respectively, without resolved hyperfine structure paramagnetic triplet (S = 1) is consistent with the anomalous value of the magnetic moment value (μeff = 1.100 and 0.99 B.M.) supporting a binuclear nature. The TG analyses confirmed the existence of solvent molecules inside and/or outside the coordination sphere. The DFT molecular modeling of ligands and its VO (IV) complexes supported the suggested geometries. Also, all compounds were screened for in vivo insulin-mimetic activity. 相似文献
11.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1992,48(5):631-637
EPR studies have been carried out on Mn(II)-doped single crystals of [Zn(H2O)6]PtCl6, [Mg(H2O)6]PtCl6 and [Cd(H2O)6]PtCl6 from room temperature to 77 K at X-band frequencies (⋍9.5 GHz). MN(II) ions substituting the divalent metals exhibit a unique magnetic behavior with the z-axes directed along the c-axes of the crystals. A non-linear iterative least-squares fitting procedure for the analysis of EPR spectra is presented. In this method calculation of the spin-Hamiltonian parameters can be carried out for any orientation of the external magnetic field with respect to the crystal symmetry axis. 相似文献
12.
V. N. Vasyukov V. A. Shapovalov V. P. Dyakonov A. F. Dmitruk E. I. Aksimentjeva H. Szymczak S. Piechota 《International journal of quantum chemistry》2002,88(4):525-529
In the temperature range between 4.2 and 300 K, the EPR spectrum of the impurity Fe3+ ion in the organic polyparaphenylene has been investigated. An effect developed as an unusual temperature change of Fe3+ EPR spectrum has been revealed. The EPR spectrum of powder sample consists of two resonance lines. Line 1 with the effective g‐value equal to g1 = 4.21 ± 0.05 is of the maximum intensity at T = 4.2 K. With temperature increase, the intensity of line 1 decreases until vanishing. Line 2 is observed over the whole temperature range. For T = 300 K, the g‐value of line 2 is g2 = 2.00 ± 0.09. To study the structure of magnetic ion molecular environment and define nonequivalent positions of the magnetic ion in polyparaphenylene, a calculation was done of the energy of Fe3+ magnetic ion for various possible molecular environments. It is shown that in polyparaphenylene for the Fe3+ magnetic ion there are two different stationary molecular environments. The obtained model of magnetic ion molecular environment was used to explain the temperature dependence of the EPR spectrum. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002 相似文献
13.
R. Hrabánski 《Chemical physics letters》1984,111(6):607-610
An EPR study has been carried out on Mn2+-doped single crystals of calcium hexachlorostannate hexahydrate [Ca(H2O)6] SnCl6 in the temperature range 77–378 K at X-band frequencies (9.3 GHz). Mn2+ ions substituting the divalent metal exhibit a unique magnetic complex with the z-axis directed along the c-axis of the crystal. The temperature dependence of the zero-field splitting parameter is discussed. 相似文献
14.
F. B. Marcotte D. Campbell J. A. Cleaveland D. T. Turner 《Journal of polymer science. Part A, Polymer chemistry》1967,5(3):481-501
The photolysis of poly(ethylene terephthalate) films was studied in vacuo with light of wavelengths 2537 and 3130 A. A very stable filter system which cuts out the 3025 A. line was developed to isolate 3130 A. from a mercury spectrum. Despite the fact that the penetration of 2537 A. light was limited to a depth of a ca. 103 A. whereas 3130 A. light was more uniformly absorbed it was possible to demonstrate that the quantum yields for CO and CO2 formation were in agreement for the two wavelengths. Quantum yields for fractures and crosslinks were estimated by sol-gel analysis. An absorption maximum which develops near 13 μ after exposure of poly(ethylene terephthalate) to light or γ-rays was attributed to the formation of groups formed by elimination of CO and CO2. ESR spectra for trapped radicals were tentatively assigned to the components p-C6H3· and ·O? CH2? CH2? . It is suggested that the former radicals combine to form crosslinks. Quantum yields (× 104) with 3130 A. light are: CO, 6; CO2, 2; crosslinks, 5.5; trapped radicals, 1.5; With 2537 A. light, quantum yields are: CO, 6–9; CO2, 2–3; the network formed was not characterized as to crosslinks and fractures; trapped radicals were observed to exist but not determined. 相似文献
15.
Note on the polymeric 8-ring structure of copper(II) dichlorophosphate According to the vibrational spectrum, the Cu atoms in Cu(O2PCl2)2 are linked to a polymeric 8-ring structure by O? P? O bridges resulting in a square planar coordination of Cu2+. From the EPR spectrum a canting angle 2γ? 104° between adjacent CuO4 planes can be deduced as an additional information. The EPR powder data are discussed with respect to an alternative structural model: 2γ may be located either within each polymeric Cu(II) complex resulting in a strongly corrugated chain structure, or all CuO4 planes of a chain may run parallel; 2γ then ought to be the angle between the CuO4 planes of different chains. 相似文献
16.
An electron paramagnetic resonance (EPR) study of FeNbO4 powder samples in monoclinic phase (wolframite-type) at X-band (8.8–9.8 GHz), in the 90–300 K temperature range, is presented. For all the temperatures, the EPR spectrum shows a single line associated with Fe3+ ions. Changes in the lineshape of the EPR spectrum, which can be attributed to Fe2+ ions, are detected at low temperatures. This behavior can be ascribed to a strong magnetic dipolar interaction between Fe2+ and Fe3+ ions. The non-resonant microwave absorption techniques: magnetically-modulated microwave absorption spectroscopy (MAMMAS) and low-field microwave absorption spectroscopy (LFMAS), were used for a further knowledge on this material. MAMMAS response suggests also the presence of Fe2+ ions, that originates a change in microwave absorption regime for T < Tp (=140 K), associated with the presence of short-range magnetic correlations. LFMAS spectra showed a linear behavior with positive slope and non-hysteretic traces. The profiles obtained by plotting the slope vs. temperature of the LFMAS line are similar to those detected by the MAMMAS technique, confirming that both types of measurement show the same processes of absorption. 相似文献
17.
M. Yoncheva E. Zhecheva R. Alcántara J.L. Tirado 《Journal of solid state chemistry》2007,180(6):1816-1825
Lithium-nickel-manganese oxides (Li1+x(Ni1/2Mn1/2)1−xO2, x=0 and 0.2), having different cationic distributions and an oxidation state of Ni varying from 2+ to 3+, were formed under a high-pressure (3 GPa). The structure and cationic distribution in these oxides were examined by powder X-ray diffraction, infrared (IR) and electron paramagnetic resonance (EPR) in X-band (9.23 GHz) and at higher frequencies (95 and 285 GHz). Under a high pressure, a solid-state reaction between NiMnO3 and Li2O yields LiNi0.5Mn0.5O2 with a disordered rock-salt type structure. The paramagnetic ions stabilized in this oxide are mainly Ni2+ and Mn4+ together with Mn3+ (about 10%). The replacement of Li2O by Li2O2 permits increasing the oxidation state of Ni ions in lithium-nickel-manganese oxides. The higher oxidation state of Ni ions favours the stabilization of the layered modification, where the Ni-to-Mn ratio is preserved: Li(Li0.2Ni0.4Mn0.4)O2. The paramagnetic ions stabilized in the layered oxide are mainly Ni3+ and Mn4+ ions. The disordered and ordered phases display different intercalation properties in respect of lithium. The changes in local Ni,Mn-environment during the electrochemical reaction are discussed on the basis of EPR and IR spectroscopy. 相似文献
18.
Preparation and Some Characteristics of Copper(I)-Copper(II) Selenocyanates From the system Cu2+-H2O-en-SeCN-in dependence on the conditions two new complexes have been prepared: Cu3en2(SeCN)(CN)3· H2O(I) and Cu3en2(SeCN)2(CN)2· H2O(II). They were studied by the methods of infra-red and EPR spectra as well as by those of X-ray diffraction. It has been found that Cu2+ is coordinated in these complexes with two molecules of ethylene diamine and one molecule water. The anion ligands have a bridging function and coordinate the copper(I). The EPR spectra show that the two complexes exhibit around the atom Cu2+ have different ligand field symmetry. For complex (I) it is a typically axial spectrum with two values of the gfactor g⊥? 2.18 and g⊥? 2.05 while complex (II) has an asymmetrical isotropic spectrum with one g-factor value only g⊥? 2.07. 相似文献
19.
Ionela Alan Angela Kriza Rodica Olar Nicolae Stanica Mihaela Badea 《Journal of Thermal Analysis and Calorimetry》2013,111(2):1163-1171
Starting from 5-bromo-N,N′-bis-(salicylidene)-o-tolidine (H2L) new complexes with Co(II), Ni(II) and Cu(II) were synthesised and characterised. The features of complexes have been assigned from microanalytical, IR, UV–Vis–NIR and EPR spectra, magnetic data at room temperature as well as thermal analysis. IR data are in accordance with bischelate nature of the deprotonated ligand that coordinates through azomethinic nitrogen and phenolic oxygen. The electronic spectra display the characteristic pattern of tetrahedral stereochemistry for [CoL]·H2O complex and octahedral one for [NiL(OH2)2]·H2O complex. The electronic spectra correlated with magnetic susceptibility measurements indicate a square-planar surrounding for [ML] (M:Ni, Cu) species, while the EPR spectrum of copper complex sustains the proposed stereochemistry. The thermal analysis evidenced that thermal transformations are complex processes according to TG, DTA and DTG curves including (crystallization or coordination) water elimination, thermolyses and oxidative degradation of Schiff base. All these processes lead to the most stable metallic oxides as final product. 相似文献
20.
The EPR spectrum of 17O? on partially reduced molybdenum oxide supported on silica-gel has been observed following adsorption of N2O at room temperature. The spectrum is chracterized by g⊥=2.019 and g|=2.002 with a|17O?=96±1 G and a|95MO,97MO=7.5±0.5 G. The O ?ion appears to undergo exchange with oxide ions at the surface. 相似文献