Exploiting conformationally gated electron transfer in self-assembled azobenzene-containing cyclic peptides using light

Abstract

An azobenzene photoswitch was incorporated into a peptide as a side chain constraint to allow interconversion between two photostationary states (PSS) comprising well-defined β-strand geometry. The peptide was covalently attached to a carbon electrode with a terminal redox-active ferrocene moiety for electrochemical interrogation of each PSS. While readily switching in solution, the increased molar volume of the cis isomer is believed to hinder the conformational change in the peptide on a self-assembled monolayer (SAM). The introduction of diluents to increase the distance between chromophores reduced these steric effects to provide on/off switching between the two photostationary states of the peptide on the SAM using alternative irradiation of UV and visible light. The structural and electronic properties of each PSS differed significantly, enabling this gated approach to exploit changes in the molecular structure that provide opportunities for the design and development of future photoswitchable peptide-based SAMs with controllable electronic functions, for applications in areas such as sensing and molecular electronics.