Voltammetric studies on the inter-relationship between the redox chemistry of TTF, TTF+˙, TTF2+ and HTTF+ in acidic media

Abstract

The electrochemistry of TTF, TTF⁺˙, TTF²⁺ and HTTF⁺ (TTF = tetrathiafulvalene) has been studied in acetonitrile (0.1 M Bu₄NPF₆) solutions containing ethereal HBF₄ or trifluoroacetic acid (TFA) using transient and steady-state voltammetric techniques. In the absence of acid, the oxidation of TTF occurs via two, diffusion controlled, chemically and electrochemically reversible, one-electron processes with reversible formal potentials of −74 and 311 mV vs. Fc^0/+ (Fc = ferrocene). The voltammetry in the presence of acid is far more complex. Voltammetric and UV-vis data reveal that the parent TTF undergoes facile protonation to yield the structurally modified HTTF⁺ cation in the presence of acid. In contrast, detailed analysis of the data show that electrochemically generated TTF⁺˙ and TTF²⁺ do not react with acid. The voltammetry in the presence of acid has been simulated to provide a thermodynamic and kinetic description of the acid–base chemistry coupled to electron transfer.