A (π-Extended Tetrathiafulvalene)−Fluorene Conjugate. Unusual Electrochemistry and Charge Transfer Properties:  The First Observation of a Covalent D2+−σ−A•- Redox State1

• Published in: Journal of the American Chemical Society 2002-11, Vol.124 (47), p.14227-14238
• Main Authors: Perepichka, Dmitrii F, Bryce, Martin R, Perepichka, Igor F, Lyubchik, Svetlana B, Christensen, Christian A, Godbert, Nicolas, Batsanov, Andrei S, Levillain, Eric, McInnes, Eric J. L, Zhao, Jing P
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja012518o

The synthesis of novel electrochemically amphoteric TTFAQ−σ−A compounds (TTFAQ = 9,10-bis(1,3-dithiol-2-ylidene)-9,10-dihydroanthracene, σ = saturated spacer, A = polynitrofluorene acceptor) is reported. Their solution redox behavior is characterized by three single-electron reduction and one two-electron oxidation waves. Electrochemical quasireversibility of the TTFAQ2+ state and a low E ox − E red gap (≈0.25 V) for 3-(9-dicyanomethylene-4,5,7-trinitrofluorene-2-sulfonyl)-propionic acid 2-[10-(4,5-dimethyl-[1,3]dithiol-2-ylidene)-9,10-dihydroanthracen-9-ylidene]-5-methyl-[1,3]dithiol-4-ylmethyl ester (10) has enabled the electrochemical generation of the hitherto unknown transient D2+−σ−A•- state as observed in cyclic voltammetry and time-resolved spectroelectrochemistry. The ground state of compound 10 was shown to be ionic in the solid but is essentially neutral in solution (according to electron paramagnetic resonance). The X-ray structure of an intermolecular 1:2 complex between 2-[2,7-bis(2-hydroxyethoxy)-9,10-bis(4,5-dimethyl-[1,3]dithiol-2-ylidene)-9,10-dihydroanthracene and 2,5,7-trinitro-4-bromo-9-dicyanomethylenefluorene, 14·(17)2, reveals, for the first time, full electron transfer in a fluorene charge-transfer complex.