J. Phys. IV France 7 (1997) C2-619-C2-620
In Situ X-Ray Absorption Studies of the Electrochemical Reduction of HydroxocobalaminM. Giorgett1, 2, I. Ascone1, M. Berrettoni3, S. Zamponi2 and R. Marassi2
1 LURE, Bât. 209D, Université de Paris-Sud, 91405 Orsay, 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
XAS fluorescence is combined with electrochemical technique to study the reduction of hydroxocobalamin (OH-Co(III)cbl) to cob(II)alamin at the cobalt K-edge. The electrochemical control permits to select a well-defined cobalt oxidation states. The experimental set-up used permits in situ reactions allowing reliable comparison among XANES spectra. The absorption edge shifts to lower energy with the progressive reduction of cobalt. The size of the peak at about 7726 eV (A peak) decrease in Co(II)cbl spectrum. Experimental XANES of OH-Co(ITI)cbl and Co(II)cbl were simulated by multiple scattering theory. Theoretical and experimental data are in agreement, peak intensity being correlated to the coordination number confirming that cobalt is five coordinate in Co(II)cbl sample.
© EDP Sciences 1997