Supramolecular and Redox Chemistry of Tetrathiafulvalene Monocarboxylic Acid with Hydrogen-Bonded Pyridine and Bipyridine Molecules

Although tetrathiafulvalene derivatives (TTFs) have been used as the redox-active unit in a lot of ion responsive receptors, only a few such examples of TTF carboxylic acids have been reported, especially about the responses to neutral organic molecules. In this work, electrochemical and spectral properties of dimethylthio-tetrathiafulvalene monocarboxylic acid (DMT-TTFCOOH) have been studied by both experimental methods and quantum chemical calculations. A square mechanism of proton transfer and electron transfer equilibriums was proposed. It is noteworthy that the process of oxidizing the TTF moiety of DMT-TTFCOOH could be controlled to obtain TTF•+ radical cation or TTF2+ dication by choosing suitable oxidizing reagents. Supramolecular responsive properties of DMT-TTFCOOH to py/bpy were investigated by cyclic voltammetry and 1H NMR spectra. The results showed that the compound DMT-TTFCOOH is an electrochemically sensitive hydrogen bonding donor that can detect a tiny difference in the hydrogen bonding acceptor molecules. The theoretical calculations further confirm the results. The hydrogen-bonding structure of DMT-TTFCOOH-bpy in crystal was solved by X-ray diffraction analysis.