Emergent Supramolecular Assembly Properties of Recognition-Encoded Oligoesters

The sequences of oligomeric molecules equipped with interacting side-chains encode the three-dimensional structure, the supramolecular assembly properties, and ultimately function. In an attempt to replicate the duplex forming properties of nucleic acids, an oligoester containing an alternating sequence of hydrogen bonding donor (D) and acceptor (A) residues was synthesised. Characterisation of assembly properties of the ADAD oligomer revealed a supramolecular architecture that resembles the kissing stem-loops motif found in folded RNA. NMR dilution and melting experiments in chloroform and 1,1,2,2-tetrachloroethane show that intramolecular hydrogen bonding interactions between the terminal phenol and phosphine oxide recognition sites in the ADAD 4-mer leads to 1,4-folding. This folded stem-loop structure can be denatured to give the single strand by heating. At higher concentrations or lower temperatures, the stem-loop dimerises via intermolecular hydrogen bonding interactions between the two inner recognition sites, leading to a kissing stem-loops structure. The results suggest a rich supramolecular chemistry for these recognition-encoded oligoesters and lay strong foundations for the future development of new functional materials based on synthetic information molecules.