Electroactive films incorporating 4,4′-Bipyridinium building blocks

Abstract

The salts of 4,4′-bipyridinium dications are becoming the basic building blocks of an increasing number of electroactive materials and devices. These compounds (1) can be prepared in good yields starting from 4,4′-bipyridine, (2) undergo two consecutive and reversible reduction processes and (3) associate with electron rich substrates as a result of electrostatic and charge-transfer interactions. The unique combination of these attractive features has stimulated the identification of experimental protocols to assemble organized films of 4,4′-bipyridinium building blocks on electrode surfaces. Relying either on the Langmuir-Blodgett technique or on self-assembly processes, monolayers of 4,4′-bipyridinium derivatives and composite multilayers of these organic compounds and inorganic nanoparticles can be prepared on a variety of solid supports. The electroactive character of the 4,4′-bipyridinium dications facilitates the characterization of the resulting materials. In general, simple voltammetric measurements provide invaluable information on the structure and properties of the electroactive films. Furthermore, the electron accepting character of the organic building blocks and their recognition properties can be exploited to design simple devices able to execute specific functions. Indeed, displays, logic gates, photodiodes, rectifiers, sensors and switches have been implemented already relying on the careful design of 4,4′-bipyridinium building blocks and their ingenious integration in nanoscaled configurations.