Relative electron donor strengths of tetrathiafulvene derivatives: effects of chemical substitutions and the molecular environment from a combined photoelectron and electrochemical study

Abstract

Interest in organic metals and superconductors has prompted studies of the effects of chemical substituents on the organic electron donor tetrathiafulvalene (TTF). Electron-donating substituents on TTF should lead to reduced ionization potentials and generally greater electron transfer in organic donor/acceptor compounds. However, the relative electron donor abilities may also be influenced by their molecular environment and intermolecular interactions. In order to address these questions, the valence ionization potentials of TTF and two derivatives, bis(ethylenedioxo)tetrathiafulvalene (BEDO-TTF) and bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF), have been measured in the gas phase by photoelectron spectroscopy and compared with oxidation potentials from solution electrochemical measurements in a variety of solvents. The order of decreasing first ionization potentials is BEDT-TTF {approx} TTF (6.7 eV) > BEDO-TTF (6.46 eV).