Charge Transfer in Single Molecules at Electrochemical Interfaces

Abstract

It is now possible to study charge transfer through single molecules at electrochemical interfaces in a wide variety of electrolytes and under full control of the electrode potentials. This has been made possible with the electrochemical scanning tunneling microscope (EC-STM). In this article, examples of single-molecule electric junctions studied under electrochemical conditions are discussed. These measurements have been made with the I(s) or in situ break junction methods using an EC-STM. This review focuses on “wired” molecular junctions where the molecule is tethered in the electric junction between the STM tip and the metal substrate. Using this configuration, it has been possible to study charge flow through a wide variety of “wired” redox-active molecular bridges, and examples discussed include viologens, pyrrolo-tetrathiafulvalene, perylene tetracarboxylic acid, anthraquinone, and ferrocene molecular wires. Such single-molecule measurements offer insights into mechanisms of charge transport through molecules at electrochemical interfaces.