Discrete Self‐Assembled Metallo‐Foldamers with Heteroleptic Sequence Specificity

• Published in: Angewandte Chemie International Edition 2021-09, Vol.60 (36), p.20027-20035
• Main Author: Preston, Dan
• Format: Article
• Language: English
• Subjects: Covalent bonds; foldamer; helix; heteroleptic; Hydrogen bonding; Metal ions; Metallography; Palladium; palladium(II); self-assembly
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202108456

Discrete and structurally diverse foldamer 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. A turn for the better: ligands with orthogonal binding‐site pairings allow the self‐assembly of discrete heteroleptic PdII‐containing sequences. These adopt persistent conformations in solution, allowing “one‐pot” metallo‐foldamer formation under thermodynamic control.