0000000000267208
AUTHOR
C. Goulon-ginet
showing 4 related works from this author
A Study Using X-ray Absorption and Emission Spectroscopy of Dioxygen-Binding Xerogels Incorporating Cyclam Units Complexed with Copper Salts.
2005
X-ray absorption spectroscopy was used to elucidate how hybrid xerogels complexed with CuCl2 could reversibly bind molecular dioxygen. Difference EXAFS analyses at the Cu K-edge suggest that dioxygen could bridge two Cu atoms in a μ-η1:η1 peroxo-like conformation with unequal Cu···O distances. Only the short distance (RCu–O1 = 1.86 ± 0.01 A) was unambiguously determined and looks typical of a CuII site. The Cu···Cu internuclear distances would be rather long: RCu–Cu ≈ 4.0 A (3.9 A) for the oxygenated (oxygen-free) xerogels. Cl K-edge EXAFS spectra revealed the pre-existence in the oxygen-free xerogels of CuI sites with short Cl–Cu bonds (2.11 ± 0.03 A). Pentacoordinate CuII sites with a lon…
XAFS Studies of High-Valent Porphyrinato Manganèse Complexes with Ozone
1997
We produce strong evidence of the interaction of ozone with a series of Manganese (III) porphyrinato complexes to form a well defined reactive intermediate. In the latter species, the Manganese atom which is formally in a tetravalent (IV) state, is (at least) hexacoordinated with the metal unambiguously lying in the basal plane of the four pyrrolic nitrogens of the porphyrin macrocycle. Substitution of Bromine or Chlorine axial ligands by ozonids is most likely to happen. This conclusion is also supported by XANES and EXAFS spectra recorded at the Chlorine K-edge which suggest that ozone may even form with chlorine a complex anion.
Structure of Dioxygen Binding Xerogels Incorporating Cyclams Complexed with CuCl2 Salts
2005
X-ray absorption/emission spectroscopies were combined in order to elucidate how hybrid xerogels complexed with CuCl2 could bind reversibly O2. Difference EXAFS analyses at the Cu K-edge revealed the existence of binuclear structures with long Cu...Cu distances, i.e. RCu–Cu ≈ 3.98 A and 3.87 A for the oxygenated and oxygen-free xerogels. In oxygenated xerogels, dioxygen would bridge two Cu atoms in a μ-η1 : η1 peroxo-like conformation. The Cu-O signal found at short distance (RCu−O1 = 1.85 ± 0.01 A) is fully consistent with 40% of O2 molecules being chemisorbed per Cu site. In oxygen-free xerogels, Cl K-edge EXAFS revealed the presence of CuI sites with short Cl-Cu bond lengths (RCl−Cu = 2.…
A Study Using Sulfur K-Edge XAS of Bitumens, Asphaltenes, Maltenes and their Oxidation Products by Comparison with Model Compounds
1997
High resolution Sulfur K-edge XANES spectra have been recorded at the ESRF on test samples of bitumen, asphaltene and maltene fractions and various model compounds. All these fractions were found to have a low content of sulfidic species as opposed to thiophenic species and it is therefore not surprising that thermally oxidized samples (RTFOT) had also a low content (1%) of sulfoxides. This is indeed consistent with the absence of any detectable S=O signature in the EXAFS spectra which were recorded over more than 1300 eV using the undulator gap scan technique.