ELECTRON-ACCEPTORS OF THE FLUORENE SERIES - 7 2,7-DICYANO-4,5-DINITRO-9-X-FLUORENES - SYNTHESIS, CYCLIC VOLTAMMETRY, CHARGE-TRANSFER COMPLEXATION WITH N-PROPYLCARBAZOLE IN SOLUTION, AND X-RAY CRYSTAL-STRUCTURES OF 2 TETRATHIAFULVALENE COMPLEXES

The synthesis and physical properties of a series of novel fluorene pi -electron accepters (7-9) are described. Cyclic voltammograms of 7 and 8 exhibit three separate reversible (or quasi-reversible) one-electro n redox waves, characteristic of strong electron accepters. Spectroele ctrochemical experiments show the appearance in the long-wavelength vi sible region of absorption bands at appropriate potentials which were attributed to the transformations A --> A(.-) and A(.-) --> A(2-). Cha rge-transfer complexation with N-propylcarbazole in dioxane shows the formation of 1:1 complexes with parameters characteristic for other fl uorene accepters. The single-crystal X-ray structures of 1:1 charge-tr ansfer complexes of tetrathiafulvalene with the electron acceptor 8 an d with the strongest fluorene acceptor 1f both show ..A...D...A...D.. stacking in the crystal.