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, P1, a = 5.9730(10) Å, b = 8.0690(10) Å, c = 29.524(3) Å; a = 95.020(10)°, ß = 93.260(10)°, ? = 97.480(10)°. The nonamphiphilic, a,?-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.