N,N-Bis(4-phenylsulfonate)-l,4,5,8-naphthalenetetracarboxylic diimide was prepared as the disodium and bis(tetrabutylammonium) salts. It was reduced electrochemically in DMF or water and by dithionite in water to a form an anion radical. On the basis of visible, NIR, IR, and ESR data, the anion radical is shown to be monomeric in DMF, dimeric in water, and aggregated in aqueous NaCl. The aggregates contain -stacks that are spectroscopically similar to the stacks found in a solid film of the anion radical.The field of organic metals is dominated by two types of molecular structures: linearly conjugated -systems such as polyacetylene, and charge-transfer complexes that form stacks of -systems in the solid state.1 In one case electrons move rapidly along a partially oxidized or reduced molecular chain. In the other, electrons move along a partially oxidized or reduced stack of molecules. In either case the electrical, optical, and magnetic properties are a complex function of the solid-state structure, and efforts have been made to prepare and study model compounds in solution. Examples of linear -conjugated systems are oligothiophenes,2 an oligoaniline,3 and oligoarylenes,4 which were oxidized in solution or in zeolites to permit investigation of the intramolecular, single-chain spectroscopic properties of the cation radicals and dications. More pertinent to the present study, which concerns -stacks in solution, is a long-chain-aryl derivatized cation radical that forms a diskotic liquid-crystal phase.5 In this case there is spectral evidence for -interactions between cation radicals, but solid salts have low conductivity and there is no evidence for extensive delocalization along the stack.In general it seems that ion radicals do not organize into delocalized -stacks in dilute solution.It is well-known, however, that ion radicals have a propensity to form -dimers in solution. The examples that have received considerable attention include Wurster's Blue (the cation radical of tetramethyl-1,4-diaminobenzene, l),6 viologen cation radicals (e.g., 2),7 and TCNQ anion radical (3).8 9In each of these cases a -complex formed at relatively high concentration in solution, which CH3X+',CH3 NC^CN 1 3
