Macroscopic Helical and Cylindrical Morphologies from Achiral 1,3-Diynes

Diacetylenes containing an anhydride function (1) or two s-triazine groups (2) precipitate from organic solvents in large helical or cylindrical forms, respectively, which have been studied by optical and scanning electron microscopy. X-ray diffraction studies on helices of 10,12-tricosadynoic anhydride, {n-C10H21C⋮CC⋮C(CH2)8CO}2O (1), show a lamellar crystalline phase with layer spacing of 42.5 ± 0.5 Å and support a noninterdigitated bilayer structure. The crystal structure of a related amphiphilic diacetylene, n-C10H21C⋮CC⋮C(CH2)8CH2OSO2C6H4Me-4 (3), is also reported and discussed: triclinic, P1̄, a = 5.9730(10) Å, b = 8.0690(10) Å, c = 29.524(3) Å; α = 95.020(10)°, β = 93.260(10)°, γ = 97.480(10)°. The nonamphiphilic, α,ω-difunctionalized diacetylene, 6,6‘-(deca-4,6-diyne-1,10-diyl)di-2,4-diamino-1,3,5-triazine, 2-{4,6-(NH2)2C3N3}(CH2)3C⋮CC⋮C(CH2)3-{C3N3(NH2)2-4,6}-2 (2), forms solid cylindrical particles of mean length ∼0.5 mm, which may derive from helix formation. The origin of macroscopic chirality in the solid-state morphology of the achiral anhydride (1) is discussed.