SELF-ASSEMBLY OF DELOCALIZED PI-STACKS IN SOLUTION - ASSESSMENT OF STRUCTURAL EFFECTS

Twelve derivatives of 1,4,5,8-naphthalenetetracarboxylic acid diimide were prepared which had cationic, anionic, or neutral substituents on the nitrogens. These imides were characterized spectroscopically and studied using cyclic voltammetry. Reduction with dithionite in water produced anion radicals, which were studied with visible, near-IR, and ESR spectroscopy. It is shown that the anion radicals self-assemble into pi-dimers and pi-stacks. The stacks are characterized by exciton bands at wavelengths greater than 1200 nm and by anisotropic ESR signals. The effect of the substituents attached to nitrogen on the extent of aggregation is explored. Most effective are cationic groups which act to balance the charge on the aromatic anion radical. The relationship of these observations to conducting stacks in solid materials is discussed.