کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
221156 | 463376 | 2006 | 13 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: The effect of solvent on the electrode process of methylcobalamine as studied by cyclic voltammetry The effect of solvent on the electrode process of methylcobalamine as studied by cyclic voltammetry](/preview/png/221156.png)
The cyclic voltammetry (CV) of methylcobalamine, Me–Cbl, was investigated as a function of solvent with different ratios of DMF/MeOH and for neat N,N-dimethylformamide (DMF) and neat dimethylsulfoxide (DMSO) in 0.1 M tetrabutylammonium fluoroborate electrolyte vs. a Ag/AgCl/Cl− reference electrode. The effect of the solvent slows the following chemical process down for DMF/MeOH ratios equal to or greater than 50% DMF. The electrode process is a chemically irreversible EC mechanism at DMF/MeOH ratios of 40:60 and 20:80 However, for the 80:20 DMF/MeOH solvent mixture, the return wave shows reoxidation of the methylcobalamine radical anion at scan rates ⩾ 100 V s−1 at room temperature. The features of this system were investigated by digital simulation of a multi-step EC mechanism of the electrode process which incorporates a scheme of squares for electroreduction of base-on and base-off forms of the MeCbl species to the base-on and base-off forms of its radical anion. The mechanism contains a series of following homogeneous reactions including Me–Co bond breaking in a solvent cage from the base-off radical anion and a final irreversible step of break-up of the caged species which gives the channel out of the scheme of squares. Simulation shows that the systems is sensitive to key parameters and gives a reasonably good fit to the experimental CV curve for the 80:20 DMF/MeOH mixture. This allows a complete parameter set of heterogeneous and homogeneous constants to be evaluated. DFT calculations (B3LYP/ LANL2DZ) indicate that the dissociation energy of Co–C bond breaking from the radical anion is less for the base-off species.
Journal: Journal of Electroanalytical Chemistry - Volume 593, Issues 1–2, 1 August 2006, Pages 74–86