[Proton NMR study of the autoassociation of ethidium bromide and of a dimer of phenanthridinium in aqueous solution].

The dilution shifts of the ethidium bromide 1 protons in aqueous solution lead to a determination of the self-association constant (K approximately 100 LM-1) and to the geometry of the complex. From these results, we propose a model for the folded form of the dimer: (4,7-diaza decamethylene) bis 5,5' (3,8-diamino-6 phenyl phenanthridinium) tetrachloride 2. All these results are discussed in relation with the biological properties of this dimer.