Effect of cobalt substitution on Li(3-2x)Co(x)N local structure: a XAS investigation.

The influence of cobalt substitution on the local structural changes around Co atoms in the layered lithium nitridocobaltates Li(3-2x)Co(x)N for 0.05 ≤ x ≤ 0.44 is investigated using Co K-edge X-ray absorption spectroscopy (EXAFS and XANES). The Co-N bond length in Li(3-2x)Co(x)N compounds is obtained vs x by performing EXAFS fitting and found to be shorter (1.80 Å) than for x = 0 (Li3N), and its value does not change with x. A comparison of EXAFS data with XRD results is discussed. We show that the continuous decrease of interlayer distance versus Co content (x), described from XRD data, accounts for an average of the Co-N and Li-N distances, weighted by the number of these bond lengths. In addition, the present work supports the proposal that the Li1b-N bonds contract with x due to a significant increase of Coulombic attractive forces locally induced by the progressive Li(+)/Co(2+) substitution. XRD studies suggested that divalent Co ions bond to two nitrogen in Li(3-2x)Co(x)N. Although additional works are still needed to prove its valence, the present XAFS findings complements the local structure found by XRD, in good accord with the electrochemical properties previously reported.

EXAFS characterization of oxaliplatin anticancer drug and its degradation in chloride media.

Oxaliplatin is a second-generation platinum-based anticancer drug. Its degradation is studied in solution, in the presence of chloride ions (in neutral or acidic media) in excess. In both cases the degradation product precipitates immediately. The EXAFS spectra of these products show that they are identical. EXAFS modeling and refinement of the first coordination sphere shows that two light atoms are replaced by two chloride ions. The complete refinement of the local structure is possible by studying the multiple-scattering signal. The results show that the main multiple-scattering contribution is due to the binding oxalato group and that the degradation product is [Cl(2)-(diaminocyclohexane)-Pt(II)].

EXAFS and IR structural study of platinum-based anticancer drugs' degradation by diethyl dithiocarbamate.

Platinum compounds constitute a discrete class of DNA-damaging anticancer drug agents, including cisplatin, carboplatin, and oxaliplatin. The toxicity of such drugs raises the problem of waste detoxification. Diethyl dithiocarbamate (DDTC) is recommended by the World Heath Organization (WHO) for the destruction of cisplatin, but the degradation product has not been structurally characterized. This paper deals with the extended X-ray absorption fine structure (EXAFS) and IR structural study of the reaction products of DDTC with cisplatin, carboplatin, and oxaliplatin. Cisplatin and carboplatin give the same reaction product: Pt(DDTC)2. In the case of oxaliplatin, we observed the formation of [(diaminocyclohexane)(DDTC)Pt(II)]. In all cases, the replacement of labile ligands by strong ligands should lead to inactive compounds. Our results suggest that the WHO inactivation protocol might be extended to carboplatin and oxaliplatin. Nevertheless, this should be validated by toxicity tests of the degradation products.