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 -C 10 H 21 C⋮C C⋮C(CH 2 ) 8 CO} 2 O ( 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 -C 10 H 21 C⋮C C⋮C(CH 2 ) 8 CH 2 OSO 2 C 6 H 4 Me-4 ( 3 ), is also reported and discussed: triclinic, P 1̄, 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-(NH 2 ) 2 C 3 N 3 }(CH 2 ) 3 C⋮C C⋮C(CH 2 ) 3 -{C 3 N 3 (NH 2 ) 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.