Interplay of weak interactions and structural features in the solid state self-assembly of symmetric diamides

Abstract

A series of symmetric diamides were synthesized as building blocks and fully characterized to understand the interplay of alkyl chain crystallization, hydrogen bonding, and rigidity of the spacer in the solid state self-assembly process. The nature of self-assembly was investigated using single crystal X-ray diffraction studies. To have a meaningful comparison of the self-assembly process, only spacer groups were changed among the diamide molecules. Diamides 1, 2, 4, and 5 showed trans conformation in the solid lattice with the dodecyl groups on either side of the molecule, whereas 3 and 6 were in the syn conformation. In the crystal lattice, diamide 1 formed Z-shaped columns, and 3 gave close packed X-shaped dimers. Diamide 6 formed linear ribbons in the solid lattice via intra- and intermolecular hydrogen bonding. In the crystal lattice of 1-5, alkyl chains were close packed and crystallized. In all crystal lattices described here, the rigidity of the spacer group along with the interplay of hydrogen bonds, alkyl chain crystallization, and packing forces dictate the formation of thermodynamically stable supramolecular architectures with various conformations in the crystal lattice.