Synthetic Molecular Rectifier of a Langmuir–Blodgett Film Based on a Novel Asymmetrically Substituted Dicyano‐tri‐ tert ‐butylphthalocyanine

A novel asymmetrically substituted dicyano‐tri‐ tert ‐butylphthalocyanine ((CN) 2 BuPc) with rectifying behavior has been synthesized. The morphology and conductive properties of (CN) 2 BuPc Langmuir–Blodgett (LB) films on mica and highly ordered pyrolytic graphite (HOPG) substrates were studied by atomic force microscopy (AFM) and scanning tunneling microscopy (STM), in air at 22 °C. The average area of each (CN) 2 BuPc molecule obtained from the AFM topography in situ is ca. 73.6 Å 2 , which is in good agreement with the result of ca. 74 Å 2 obtained from the π– A isotherm curve of a LB film. This indicates that the molecules are standing edge‐on, tilted by 38° against the surface normal of the substrate. The conductive properties for the 7‐layer LB films of (CN) 2 BuPc were studied by STM with a tungsten tip. The asymmetric I – V curve revealed a type of rectifying behavior for a negative and a positive bias. A feature model of the intramolecular and intermolecular charge transfer is presented. It not only interprets electron transfer from electron‐donor to electron‐acceptor molecules via a molecular “bridge”, but also the tunneling effect through intermolecular charge transfer.