American Chemical Society, Journal of Organic Chemistry, 6(81), p. 2581-2588, 2016
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On mixing equimolar solutions of the enantiomeric naphthalenediimide-based highly rigid triangles R-delta and S-delta in ClCH2CH2Cl, the racemate rac-delta forms an organogel which is composed of interwoven fibers, resulting from the columnar stacking of the triangles in an alternating R-delta/S-delta fashion. Under identical conditions, the pure enantiomers do not form organogels. DFT Calculations reveal that the racemic (RS)-dimer is more stable than the (RR)-dimer as a result of the enantiomeric relationship between R-delta and S-delta allowing them to act as two complementary rings comprised of 12 [C–H...O] interactions with an unprecedented and uninterrupted circular ADDAADDAADDA.DAADDAADDAAD alignment of hydrogen bond donors (D) and acceptors (A), in contrast with the square-wave manner in which the (RR)-dimer forms a complementary, yet interrupted ADADAD.DADADA circular sequence of six longer [C–H...O] hydrogen bonds. It follows that gelation is favored by weak interactions acting cooperatively in rings under precise stereoelectronic control.