Foldamer engineering with squaramide and phenanthroline motifs: synthesis, characterisation, and structural insights

We report a new class of phenanthroline-squaramide foldamers (1-3) that adopt robust, single-helical conformations in both solution and the solid state, stabilised by intramolecular hydrogen bonding and π-π stacking. Structural integrity was confirmed by single-crystal X-ray diffraction and NMR spectroscopy. Notably, the helical architectures are highly robust, displaying remarkable resistance to disruption by competitive solvents (e.g., DMSO) and maintaining their structure at elevated temperatures (up to 85 °C), as confirmed by variable-temperature NMR studies. These findings highlight the potential of phenanthroline-squaramide foldamers as robust and tunable platforms for supramolecular chemistry and responsive molecular systems.