Crystal structures of three new N-halo­methyl­ated quaternary ammonium salts

In the crystals of the title N-halo­methyl­ated quaternary ammonium salts, C(19)H(23)IN(+)·I(−), (I) [systematic name: N-(4,4-di­phenyl­but-3-en-1-yl)-N-iodo­methyl-N,N-di­methyl­ammonium iodide], C(20)H(25)IN(+)·I(−), (II) [systematic name: N-(5,5-di­phenyl­pent-4-en-1-yl)-N-iodo­methyl-N,N-di­methyl­ammonium iodide], and C(21)H(27)IN(+)·I(−), (III) [systematic name: N-(6,6-di­phenyl­hex-5-en-1-yl)-N-iodo­methyl-N,N-di­methyl­ammonium iodide], there are short I⋯I(−) inter­actions of 3.564 (4), 3.506 (1) and 3.557 (1) Å for compounds (I), (II) and (III), respectively. Compound (I) crystallizes in the Sohncke group P2(1) as an ‘enanti­opure’ compound and is therefore a potential material for NLO properties. In the crystal of compound (I), mol­ecules are linked by C—H⋯I(−) and C—H⋯π inter­actions which, together with the I⋯I(−) inter­actions, lead to the formation of ribbons along [100]. In (II), there are only C—H⋯I(−) inter­actions which, together with the I⋯I(−) inter­actions, lead to the formation of helices along [010]. In (III), apart from the I⋯I(−) inter­actions, there are no significant inter­molecular inter­actions present.