Discrete self-assembled metallo-foldamers with heteroleptic sequence specificity.

Foldamers are molecular sequences which contain structural information: the shape they adopt in solution depends on the identity and the ordering of the components that comprise the sequence. As such the fidelity of the sequence is essential, and enables the reliable formation of secondary structures that act as the scaffolds to enable many molecular functions. Discrete and structurally diverse sequences are constructed in both natural and abiotic systems primarily using inert connectivity with irreversible organic covalent bonds, serving to preserve the identity of the sequence. The formation of sequences under thermodynamic control using labile coordination bonds would be attractive for synthetic ease and modular capability, but this presents issues regarding sequence preservation. Here is presented an approach integrating palladium(II) metal ions into the sequence itself, with fidelity maintained through use of complementary pairings of ligand arrangements at the metal centre. This is accomplished using sites of different denticity and/or hydrogen bonding capability. In this fashion, discrete and ordered metallo-sequences are formed as thermodynamic products in a single step, and these then fold into defined conformations due to π-π interactions between electron rich and poor aromatic regions of the combined componentry.