Single Molecule Study of the Electronic Structures of Molecular Tripods with Functional Units

Abstract

  We have studied the adsorption of molecular tripods, having a Br atom (BATT) and a ferrocene derivative (Ferrocene-ATT) at the head position of the adamantane-based trithiolate, on Au(111) using scanning tunneling microscopy (STM). BATT forms well-ordered self-assembled monolayer (SAM), of which the structure is same as that of Ferrocene-ATT. This indicates that the functional unit connected to the head part of the adamantane-based trithiolate does not affect the molecular ordering of SAMs. The electronic structures of individual adamantane-based molecular tripods were evaluated using scanning tunneling spectroscopy (STS). While the STS spectrum of BATT has almost no feature at near the Fermi level, the electronic state, i.e., highest occupied molecular orbital (HOMO), of Ferrocene-ATT, was clearly observed in the same spectrum range when taken at the well-ordered SAM. STS mapping revealed the distribution of the HOMO state of Ferrocene-ATT, which indicates the rotational motion of the ferrocene unit.