Photo-induced vectorial electron transfer through oriented metal-coordinated peptide assembly on a self-assembled monolayer

A vertically and unidirectionally oriented metal-coordinated α-helical peptide assembly having an amino acid sequence of Leu2His(Co(II))Leu6His(Co(II))Leu6-C60 was fabricated on a mixed self-assembled monolayer (SAM) surface consisting of amino-alkanethiol, dialkyl disulfide, and ferrocenyl alkanethiol by a stepwise polymerization of the amino acids using the modified conventional solid-phase peptide synthesis. We have demonstrated that vectorial electron transfer through the peptide assemblies on the mixed SAM. The Co(II)-His complexes in the peptide assembly on the SAM accelerated the electron transfer coupled with the macro-dipole moment of the peptides through the assembly. Furthermore, upon photo-irradiation to the peptide assembly, electron transfer occurred from the excited ferrocenyl group on the SAM surface to the electron acceptor, C60, at the terminal through the metal-coordinated α-helical peptide assembly. This method has the advantage of permitting simple fabrication of oriented peptide assemblies consisting of sequential peptides having functional groups such as electron donors and acceptors at the desired positions. This system may be useful for signal transduction devices.