Tubular and lamellar hydrogen-bonding molecular assemblies of isophthalic acid derivatives bearing a –CONHC(n)H(2n+1) chain

Isophthalic acid derivatives (CnIP), bearing alkylamide chains (–CONHC(n)H(2n+1): n = 6, 10, 14, and 18) at the 5-position that can participate in hydrogen bonding, were prepared and evaluated for their hydrogen-bonding molecular assembly structures for organogelation and liquid crystal formation. The hydrogen-bonding carboxylic acid (–COOH) groups form a ring-shaped (CnIP)(6) hexamer or a one-dimensional (1D) zig-zag (CnIP)(∞) chain. Although neither organogelation nor liquid crystal formation was observed in the isophthalic acid derivative bearing an alkoxy (–OC(14)H(29)) chain, C14IP and C18IP derivatives could form both organogel and liquid crystal states through intermolecular N–H⋯O = amide-type hydrogen-bonding interactions. A discotic hexagonal columnar liquid crystal (Col(h)) phase was observed in hydrated (C14IP)(6)·(H(2)O)(n) and (C18IP)(6)·(H(2)O)(n), whereas a lamella-type liquid crystal (L(a)) phase was confirmed in the unhydrated C18IP. In the Col(h) phase, O–H⋯O hydrogen-bonding ring-shaped (C14IP)(6) and (C18IP)(6) hexamers assembled to form the tubular molecular assembly stabilized by intermolecular–N–H⋯O = hydrogen-bonding interactions along the tube growth direction, where H(2)O molecules were contained within the hydrophilic space. On the other hand, the N–H⋯O = hydrogen-bonding interactions between the 1D zig-zag (CnIP)(∞) chains formed a layer-type molecular assembly of the L(a)-phase in the absence of water molecules.