A Tetrathiafulvalene-inserted Diphenoquinone: Synthesis, Structure and Dynamic Redox Property.

We synthesized a novel tetrathiafulvalene (TTF) derivative substituted with two phenoxy radicals on one 1,3-dithiole ring, which may have either open-shell diradical or closed-shell extended-quinoidal ground states. X-ray single crystal analysis and NMR measurements proved that this molecule has a closed-shell extended quinoidal structure both in the solid state and in solution. DFT calculations showed the donor-acceptor type electronic properties of this molecule with well-separated HOMO-LUMO distribution and a small HOMO-LUMO energy gap. Because of this donor-acceptor type character, this molecule gave both the dication and the dianion species by electrochemical oxidation and reduction. Furthermore, during the redox process between the neutral and the dication states, this molecule exhibited unique changes in the cyclic voltammogram by repeating the cycles or varying the scan rate. The observed electrochemical behavior was explained by the conformational changes of the electrochemically generated species, and thus indicating that this molecule is classified as a dynamic redox system.