In the title compound (systematic name: 3,8-diamino-5-ethyl-6-phenylphenanthridin-5-ium 2,2,3,3,4,4,4-heptafluorobutyrate), C21H20N3+·C4F7O2−, two ethidium ions, C21H20N3+ form a dimerized structure due to π–π interactions, even though they are positively charged. The heptafluorobutyrate anions are connected to neighbouring cation dimers via hydrogen-bonding interactions, the hydrogen-bonding donor sites of the –NH2 groups of the ethidium ions connecting to the hydrogen-bonding acceptor sites of the –COO− groups of the heptafluorobutyrate anions.
