π–π interactions modulate charge transport in peptide-based frameworks

Abstract

Particular interest has been focused on the modulation of solid state charge transport in proteins via π–π interactions. Nevertheless, molecular design with the π–π interaction mode for electronic applications remains a challenge in light of the complexity of protein structures. Here, we investigate the pattern of regulating peptide charge transport via different types of π–π interactions in peptide-based frameworks. We applied aromatic amino acid containing peptides labelled with a 1-methyl-1′-aminoethyl-4,4′-bipyridinium salt (MV²⁺) to construct well-defined self-assembled monolayers as the model. When the π–π interactions are improved by the size of aromatic amino acid side chains, the peptide charge transport can be promoted mainly by the reduced energy barrier and not by the weakened peptide−electrode coupling. When the π–π interactions are attenuated rapidly by increasing the distance between aromatic groups, the molecule–electrode coupling is enhanced sharply, which becomes the main factor to facilitate the charge transport.