A systematic study of the variation of tetrathiafulvalene (TTF), TTF+˙ and TTF2+ reaction pathways with water in the presence and absence of light

Abstract

The chemistry of the strongly electron donating tetrathiafulvalene (TTF) molecule is exceptionally well known, but detailed knowledge of the chemistry of its technologically important one (TTF⁺˙) and two (TTF²⁺) electron oxidised redox partners is limited. In this paper, the different pathways that apply to the reaction of TTF, TTF⁺˙ and TTF²⁺ with water have been identified in the absence and presence of light. On the basis of data obtained by transient and steady state voltammetric methods in CH₃CN (0.1 M Bu₄NPF₆) containing 10% (v/v) H₂O, TTF is shown to participate in an acid base equilibrium reaction with HTTF⁺, with H₂O acting as the proton donor. In contrast, TTF⁺˙ generated by one electron bulk oxidative electrolysis of TTF remains unprotonated and fully stable in the presence of 10% H₂O in the dark. However, when this cation radical is exposed to white or blue (λ = 425 nm) light, TTF⁺˙ is photoreduced to TTF, with oxidation of water to give oxygen (detected by a Clark electrode) and protons that react with TTF to give HTTF⁺ as the counter reaction. Again emphasising important reaction pathway differences associated with each redox level, TTF²⁺ generated by bulk two electron oxidative electrolysis of TTF reacts rapidly with water, even in the dark, to give TTF⁺˙, protons, HTTF⁺ and oxygen as the products.