Three-dimensional crystalline supramolecular nanostructures from self-assembly of rod-coil molecules incorporating lateral carboxyl group in the middle of the rod segment

We report the synthesis and self-assembling behaviour of coil-rod-coil molecules 1a-1c and 2a-2c, which incorporate lateral carboxyl or ester groups in the middle of the rod segment. The self-assembling behaviour of these molecules was investigated in the bulk using differential scanning calorimetry, polarised optical microscopy and small-angle X-ray scattering. Our results reveal that hydrogen bonds strongly influence the self-assembling behaviour of rod-like building blocks. Molecules 1a-1c, which incorporate carboxyl groups in the middle of rod segments, self-assemble into two-dimensional (2-D) columnar, three-dimensional (3-D) body-centred tetragonal and 3-D hexagonal close-packed assemblies in the crystalline state. However, molecules 2a-2c, which contain ester groups in the centre of rod segments, self-assemble into unexpected lamellar, hexagonal perforated lamellar and 2-D columnar nanostructures in the bulk, indicating that hydrogen bonds impede intermolecular stacking in this rod-coil system. (c) 2015 Society of Chemical Industry