Crystal Engineering of Supramolecular 1,4‐Benzene Bisamides by Side‐Chain Modification – Towards Tuneable Anisotropic Morphologies and Surfaces

Abstract

Benzene bisamides are promising building blocks for supramolecular nano‐objects. Their functionality depends on morphology and surface properties. However, a direct link between surface properties and molecular structure itself is missing for this material class. Here, we investigate this interplay for two series of 1,4‐benzene bisamides with symmetric and asymmetric peripheral substitution. We elucidated the crystal structures, determined the nano‐object morphologies and derived the wetting behaviour of the preferentially exposed surfaces. The crystal structures were solved by combining single‐crystal and powder X‐ray diffraction, solid‐state NMR spectroscopy and computational modelling. Bulky side groups, here t‐butyl groups, serve as a structure‐directing motif into a packing pattern, which favours the formation of thin platelets. The use of slim peripheral groups on both sides, in our case linear perfluorinated, alkyl chains, self‐assemble the benzene bisamides into a second packing pattern which leads to ribbon‐like nano‐objects. For both packing types, the preferentially exposed surfaces consist of the ends of the peripheral groups. Asymmetric substitution with bulky and slim groups leads to an ordered alternating arrangement of the groups exposed to the surface. This allows the hydrophobicity of the surfaces to be gradually altered. We thus identified two leitmotifs for molecular packings of benzene bisamides providing the missing link between the molecular structure, the anisotropic morphologies and adjustable surface properties of the supramolecular nano‐objects.

Highly Efficient Supramolecular Nucleating Agents for Poly(3-hexylthiophene)

“…Apart from the numerous structural motifs which were used to achieve supramolecular (nano)­objects and act as nucleating agents, we selected C2-symmetrical linear structures such as 1,4-benzenebisamides and 1,4-cycloehexanebisamide derivatives. These compounds are known to form a one-dimensional strand of hydrogen bonds, resulting in platelet or ribbon-like structures on the nano and mesoscale. , In particular, at least two opposite surfaces in these structures form a very regular and linear sequence of their used side groups, which may serve as nucleation sites for the extended P3HT backbone. For this, we explored a set of supramolecular nucleating agents for the semiconducting polymer, P3HT, consisting of four structurally similar bisamides NA 1– NA 4 , each featuring two peripheral 4-pyridine moieties.…”