J. Phys. IV France 7 (1997) C2-621-C2-622
XAS Studies on "Costa Type" Model Compounds of Coenzyme B12M. Giorgetti1, 2, M. Berrettoni2, R. Marassi2, A. Di Cicco3 and I. Ascone1
1 LURE, Bât. 209D, Université de Paris-Sud, 91405 Orsoy, France
2 Dip. Scienze Chimiche, via S. Agostino 1, 62032 Camerino (MC), Italy
3 Dip. Matematica e Fisica, via Madonna delle Carceri, 62032 Camerino (MC), Italy
We report XAS studies on several "Costa type" compounds with different alkyl groups in the axial position. Especially the XANES part of the spectra shows differences in the electronic and structural features due to the different electronic donor power of the substituent and to a variation of the degree of the octahedral symmetry around the metal site. The EXAFS analysis, performed by using the package GNXAS, has permitted the study of the Co-C bond length dependence on the chemical nature of the alkyl group. The bond length appears to depend on the Taft σ* constant of the alkyl group. The relationship between the information obtained by EXAFS and XANES analysis is also discussed.
© EDP Sciences 1997