Rectification in supramolecular zinc porphyrin/fulleropyrrolidine dyads self-organized on gold(111).
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 (PyC(2)C(60)) axially ligated to zinc(II) tetraphenylporphyrin (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 behavior in tunneling spectroscopy. First-principles density functional theory calculations clarify the conformational and electronic properties of the 4-ATP/ZnTPP/PyC(2)C(60) 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 behavior cannot be explained as an elastic resonant tunneling process, but it can by using a model based on the Aviram-Ratner mechanism.
National Nanotechnology Laboratory (CNR-INFM), Distretto Tecnologico ISUFI, Università del Salento via Arnesano, 73100 Lecce, Italy.
Francesca
F
Matino
Valentina
V
Arima
Manuel
M
Piacenza
Fabio
F
Della Sala
Giuseppe
G
Maruccio
Ray J
RJ
Phaneuf
Roberta
R
Del Sole
Giuseppe
G
Mele
Giuseppe
G
Vasapollo
Giuseppe
G
Gigli
Roberto
R
Cingolani
Ross
R
Rinaldi