Informace o publikaci

Differences of redox behaviour of ferrocene derivatives in buffered and unbuffered aqueous solutions



Rok publikování 2018
Druh Článek ve sborníku
Konference XVIII. Workshop of Biophysical Chemists and Electrochemists
Fakulta / Pracoviště MU

Středoevropský technologický institut

Klíčová slova Ferrocene; Aminoferrocene; Buffered; Unbuffered; Proton-coupled electron transfer; cyclic voltammetry; Square wave voltammetry
Popis Aminoferrocene possesses amino group tethered to one of the cyclopentadienyl groups, which makes it attractive for use in areas such as peptide bioconjugation, prodrug synthesis, and as electroactive indicator for biosensors. While there exists a lot of reports describing use of aminoferrocene (FcNH2) in organic synthesis, not much work has been devoted to its electrochemical properties. During our work, we have noticed unexpected behaviour of FcNH2 when measuring its redox potential in aqueous solutions of different pH using common electrochemical methods. Since FcNH2 contains single protonable group, firstly we have decided to investigate its redox behaviour in aqueous solutions of different pH values. In buffered solutions FcNH2 exhibits a single peak in square wave voltammetry and its peak potentials are varying linearly across a broad pH range (2-6.5). There seems to be no major difference between stirred and unstirred solution apart from increased noise in the voltammetric records of stirred solutions. On the contrary, a pair of peaks is distinct in unbuffered solutions when pH of the solution is close to the pKa of FcNH2 (pKa = 5.76). Stirring the solution shifts the voltammetric spectra in favour of the form with higher redox potential. Since, the relative distribution of forms greatly changes with both stirring and scan rate, we assume that the effect is caused by both mass and charge transfer across the metal/solution interface. Moreover, two distinct forms in unbuffered solutions were observed in our work with ferroceneboronic acid, however, only a single form in buffered solution (not in article). Similar disparity in behaviour was also observed with flavins in buffered and unbuffered solutions; but here the oxidation/reduction is directly coupled with protonation/deprotonation. In our contribution, redox behaviour of various ferrocene derivatives was studied in dependency on pH of the solution. Specific mechanistic conclusions were made for each ferrocene derivative and effect of buffered and unbuffered environment will be assumed.

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