A highly stable double helix of aromatic oligoamide comprised of fused ring aromatic units

Aromatic oligoamides of 2,6-diaminofluorobenzene and 1,8-diazafluoroanthrancene-2,7-diacid have been synthesized by a convergent method. The heptameric oligoamide can not only fold into a single helix but also hybridize into a highly stable double helix through intensive intermolecular aromatic stackings, which has been extensively characterized in the solid state by single crystal X-ray diffractions and in solution by 1H NMR, NOESY, and UV/vis spectra. The Kdim values of the heptamer are over 107 L mol−1 in various solutions at rt. The extensive interstrand interactions, enlarged diameter (5.4 Å), and lower torsion angles (13°) render heptamer 1 readily to hybridize into a highly stable double helix based on spring-like extension mechanism.