Search results for "ELECTRON PARAMAGNETIC RESONANCE"
showing 10 items of 565 documents
Eu2+ Stabilization in YAG Structure: Optical and Electron Paramagnetic Resonance Study
2016
A set of Eu-doped Y3Al5O12 (YAG) phosphors in the powder form was successfully synthesized by multiple-step solid-state reaction under the reducing Ar:5%H2 atmosphere. Their physical properties were investigated by means of X-ray diffraction, time-resolved luminescence spectroscopy, and electron paramagnetic resonance (EPR). Special attention was given to well-grounded confirmation of Eu2+ occurrence in the YAG structure. X-ray diffraction confirmed the presence of a major YAG phase in all samples. The influence of Eu concentration, form of doping (EuS, EuF2, or Eu2O3) and number/form of annealing steps was studied. Corresponding characteristics were measured and evaluated in a broad temper…
Hot electron injection into aqueous electrolyte solution from thin insulating film-coated electrodes
1998
Hot electron injection into aqueous electrolyte solution was studied with electrochemiluminescence and electron paramagnetic resonance (EPR) methods. Both methods provide further indirect support for the previously proposed hot electron emission mechanisms from thin insulating film-coated electrodes to aqueous electrolyte solution. The results do not rule out the possibility of hydrated electron being as a cathodic intermediate in the reduction reactions at cathodically pulse-polarized thin insulating film-coated electrodes. However, no direct evidence for electrochemical generation of hydrated electrons could be obtained with EPR, only spin-trapping experiments could give information about…
Synthesis and molecular and electronic structures of a series of Mo3CoSe4 cluster complexes with three different metal electron populations.
2008
The synthesis, crystal structure, and magnetic properties of [Mo 3(CoCO)Se 4(dmpe) 3Cl 3] ( 1), [Mo 3(CoCl)Se 4(dmpe) 3Cl 3] ( 2), and [Mo 3(CoCl)Se 4(dmpe) 3Cl 3](TCNQ) ([ 2](TCNQ)) (dmpe = 1,2-bis(dimethylphosphanyl)ethane; TCNQ = 7,7,8,8-tetracyanoquinomethane) cubane-type complexes with 16, 15, and 14 metal electrons, respectively, are reported. These compounds complete the series of cobalt-containing Mo 3CoQ 4 (Q = S, Se) cubane-type complexes, which allows a complete analysis of the consequences of replacing the inner chalcogen and the metal electron count on the structural, magnetic, and electrochemical properties. The experimental evidence is theoretically supported and rationalized…
Crystal and molecular structure and electronic properties of [Cu(phen)2(HL)] · (phen)0.5 · 7H2O (H3L = 1,3,5-triazine-2,4,6(1H,3H,5H)-trione), a nove…
1998
Abstract The crystal and molecular structure of [Cu(phen)2(HL) · (phen)0.5 · 7H2O (H2L = 1,3,5-triazine-2,4,6(1H,3H,5H)-trione) has been determined by X-ray diffraction methods. The structure is built up of neutral [Cu(phen)2(HL)] entities (which are associated to form dinuclear units through hydrogen bonds involving the cyanurate ions), uncoordinated phenanthroline and crystallisation water molecules. The copper atom is involved in a CuN5 chromophore, with an stereochemistry near to a compressed trigonal bipyramid (TBP) but with a significant degree of distortion towards the square pyramidal (SP) topology. The EPR spectrum is indicative of a mixed d z 2 d x 2 −y 2 ground state for the copp…
Oxidomolybdenum(IV), ‐(V), ‐(VI) Complexes with Relevance to Molybdenum Enzymes: Oxygen Atom Transfer, Redox Chemistry and EPR Spectroscopy
2010
The cis-dioxidomolybdenum(VI) complex Mo(NN′)2O2 (1) [(NN′) = N-(4-hydroxyphenyl)-2-pyrrolatocarbaldimine] transfers one oxygen atom to phosphanes PMenPh3–n (n = 0–3) to give quantitatively the respective phosphane oxides OPMenPh3–n (OAT, oxygen atom transfer). The kinetics of these OAT reactions has been investigated spectrophotometrically. When offering excess PMenPh3–n (n = 1–3), oxido(phoshane)molybdenum(IV) complexes Mo(NN′)2O(PMenPh3–n) 5a–5c are isolated and characterized by multinuclear NMR spectroscopy (1H, 13C, 31P, 15N), IR spectroscopy, UV/Vis spectroscopy and mass spectrometry. The redox chemistry of the molybdenum(IV) complexes 5a–5c and of molybdenum(VI) complex 1 has been pr…
Dicopper(II) Metallacyclophanes with Oligo(p-phenylene-ethynylene) Spacers: Experimental Foundations and Theoretical Predictions on Potential Molecul…
2013
Two novel double-stranded dicopper(II) metallacyclophanes of formula (nBu4N)4[Cu2(dpeba)2]·4MeOH·2Et2O (1) and (nBu4N)4[Cu2(tpeba)2]·12H2O (2) have been prepared by the Cu(II)-mediated self-assembly of the rigid ('rod-like') bridging ligands N,N'-4,4'-diphenylethynebis(oxamate) (dpeba) and N,N'-1,4-di(4-phenylethynyl)phenylenebis(oxamate) (tpeba), respectively. Single crystal X-ray diffraction analysis of 1 confirms the presence of a dicopper(II)tetraaza[3.3]4,4'-diphenylethynophane metallacyclic structure featuring a very long intermetallic distance between the two square planar Cu(II) ions [r = 14.95(1) Å]. The overall parallel-displaced π-stacked conformation of the two nearly planar par…
3D-transition metal mono-substituted Keggin polyoxotungstate with an antenna molecule: synthesis, structure and characterization
2008
Three new organic-inorganic hybrid complexes based on 3d-transition metal monosubstituted Keggin polyoxometalates (POMs) with imidazole (Im) as pendant ligands, formulated as (HIm)(6-)[SiW11O39NiIm]0.8[SiW11O39Ni(H2O)]0.2.7H2O (1), (Im)4Na6[SiW11O39MnIm]0.69[SiW11O39Mn(H2O)]0.31.7.5H2O (2) and (HIm)6[SiW11O39CoIm]0.63[SiW11O39Co(H2O)]0.37.7H2O (3), have been synthesized and characterized by IR spectroscopy, UV-visible spectroscopy, elemental analysis, TG analysis, cyclic voltammetry, magnetic properties, EPR and single-crystal/powder X-ray diffraction. The structural analyses indicate that the 3d metal atoms are incorporated into the vacancy of the alpha-[SiW11O39](8-) (SiW11). Complexes 1-…
Paramagnetic aluminium β-diketiminate
2012
The β-diketiminate ligand framework is shown to undergo reduction to form a neutral main group radical stabilized by spiroconjugation of the unpaired electron over the group 13 element centre. The synthesized paramagnetic complex was characterized by EPR spectroscopy and computational chemistry.
Preparative, structural, and electrochemical investigations on peralkylated niobocene dichlorides and difluorides
1994
CP(dagger)2NbCl2 (CP(dagger) = 175-C5Me4Et) (1b) was synthesized from NbCl5 and a slight excess of Cp(dagger)Li and NaBH4. Its electrochemical (2 e-, E1/2 = -1.6 V) and chemical reduction (2 equiv of Na/Hg) was studied showing that peralkylation of the Cp ligand facilitates two-electron reduction compared to less substituted CP2NbHal2 derivatives. The reduced solutions of CP*2NbCl2 (CP* = C5Me5) (1a) and of lb were shown by means of EPR spectroscopy to contain two new paramagnetic species 1A,B for which bent niobocene (A(Nb) = 100 G) and fulvene-like structures (A(Nb) = 55 G) are proposed. The high reduction potential of these species led in their reaction with HPF6 to the first stable difl…
Electron paramagnetic resonance and magnetic circular dichroism of Gd3+ ions in oxyfluoride glass–ceramics containing CaF2 nanocrystals
2015
Abstract Magnetic resonance investigations of the Gd3 + centre structure in the oxyfluoride glass and glass–ceramics (GCs) have been carried out. The electron paramagnetic resonance (EPR) measurements showed the presence of low symmetry Gd3 + centres in the glass sample. The cubic Gd3 + centre appeared in the glass–ceramics after heat treatment of the samples at temperatures above 650 °C. The magnetic circular dichroism (MCD) measurements of both glass and glass–ceramics showed wide absorption band around 310 nm. In the GC samples MCD–EPR of the cubic Gd3 + centre has been detected.