Diastereoselective homochiral self-assembly occurs in solution by mixing the propeller-like racemic tris(DEAS-bpy) ruthenium(II) cation B [DEAS-bpy = 4,4'-bis(diethylamino[TRISPHAT = tris(tetrachlorobenzenediolato)phosphate(V)]. This phenomenon is clearly shown by 1H NMR spectroscopic studies which reveal: (i) the existence of a rapid equilibrium between their homochiral and heterochiral associations, (ii) at room temperature, the preferential formation of the homochiral ion pairs with a ratio homochiral/heterochiral = 72:28, and (iii) at 243 K, the almost pure homochiral associations (B?,A?2) and (B?,A?2).