Self-assembly of cis- and trans-cyclic-1,2-diols. Supramolecular synthon equivalence between cis-1,2-diols and primary amides

Inspite of the fact that the self-assembly of compounds containing hydroxyl group has been enormously documented in the literature, our studies with aliphatic cyclic diols have offered the unique opportunity to examine the self-assembly of gauche and anti forms of ethylene glycol. Whereas the cis-diols are found to form dimers that infinitely assemble further to yield tapes, the anti-diols are found to form linear chains that link up further to yield molecular tapes. Notably, both the isomers lead to molecular tapes, which have attracted immense attention since the inception of self-assembly for controlling molecular organization. Quite remarkably, the self-assembly observed with cis-diols establish a formal equivalence between supramolecular synthons associated with cis-1,2-diols and primary amides. Although the assembly of diols is akin to the tape structure adopted by primary amides, we prefer to view the association of diols as a ladder. The structures of 5-cis and 8-cis are both step-ladder assemblies. That formed by 5-trans is a new variant termed as rope-ladder assembly. The ring motifs observed in the crystal packing suggest for further scope in exploiting the polyhydroxyl compounds for self-assembly in a predictive manner.