Engineering Two-Helix Motifs through NDI Linker: A Modular Approach for Charge Transferable Conductive Foldamers Design

A new approach for the construction of two-helix motifs from helix modules and planar 1,4,5,8-naphthalenetetracarboxylic diimide (NDI) is described. The single crystal conformations of two different types of two-helix motifs consisting of achiral α-peptide C₁₀-helix (3₁₀) and chiral α,γ-hybrid peptide C₁₂-helix revealed that the helices adopted antiparallel orientations across the planar NDI with 2-fold symmetry. The crystal conformations of two-helix motifs were further explored to design electrical conducting peptide foldamer by introducing electron rich pyrene (p-type) as a side-chain in the α,γ-hybrid helix. The two-helix motif with charge transferable pyrene (p-type)-NDI (n-type) combination showed better electrical conductivity compared to the two-helix motif without pyrene side-chain. Moreover, the crystal conformations also provided molecular insight into the peptide orientation of NDI-peptide conjugates. The two-helix motifs described here may serve as potential molecular scaffolds to design novel conductive peptide foldamers and self-assembling biomaterials.