Just another WordPress site - Ruhr-Universität Bochum

Self-assembled donor/acceptor dyads are of current interest as they are biomimetic to the natural photosynthetic conversion system. Herein, we present an ultrahigh-vacuum scanning tunneling microscopy and scanning tunneling spectroscopy. (UHV-STM/STS) study of ex-situ self-assembled supramolecular dyads consisting of fulleropyrrolidines (PyC₂C₆₀) axially ligated to zinc(II) tetraphenylprophyrin (ZnTPP), self organized on a 4-aminothiophenol (4-ATP) self-assembled monolayer on gold-(111). These dyads show both bias polarity-dependent apparent height in STM images and highly rectifying behaviour in tunneling spectroscopy. First-principles, density functional theory calculations clarify the conformational and electronic properties of the 4-ATP/ZnTPP/PyC₂C₆₀ system. Interestingly, we find easier tunneling for electrons moving from the acceptor side of the dyads to the donor side, in the inverse-rectifying sense with respect to previously reported molecular rectifiers. Such behaviour cannot be explained as an elastic resonant tunneling process, but it can by using a model based on the Aviram-Ratner mechanism.