The structures of three compounds with potential antimalarial activity are reported. In N,N-diethyl-N'-(7-iodoquinolin-4-yl)ethane-1,2-diamine, C15H20IN3, (I), the molecules are linked into ribbons by N-H...N and C-H...N hydrogen bonds. In N-(7-bromoquinolin-4-yl)-N',N'-diethylethane-1,2-diamine dihydrate, C15H20BrN3.2H2O, (II), two aminoquinoline molecules and four water molecules form an R5(4)(13) hydrogen-bonded ring which links to its neighbours to form a T5(2) one-dimensional infinite tape with pendant hydrogen bonds to the aminoquinolines. The phosphate salt 7-chloro-4-[2-(diethylammonio)ethylamino]quinolinium bis(dihydrogenphosphate) phosphoric acid, C15H22ClN3(2+).2H2PO4-.H3PO4, (III), was prepared in order to establish the protonation sites of these compounds. The phosphate ions form a two-dimensional hydrogen-bonded sheet, while the aminoquinoline cations are linked to the phosphates by N-H...O hydrogen bonds from each of their three N atoms. While the conformation of the quinoline region hardly varies between (I), (II) and (III), the amino side chain is much more flexible and adopts a significantly different conformation in each case. Aromatic pi-pi stacking interactions are the only supramolecular interactions seen in all three structures.