Perepichka, D.F., Bryce, M.R., Perepichka, I.F., Lyubchik, S.B., Christensen, C.A., Godbert, N., Batsanov, A.S., Levillain, E., McInnes, E.J.L., Zhao, J.P., "A (π-extended tetrathiafulvalene)-fluorene conjugate. Unusual electrochemistry and charge transfer properties: The first observation of a covalent D²⁺–σ–A˙⁻ redox state", Journal of the American Chemical Society, 2002