3,4-Ethylenedioxythiophene (EDOT) as a versatile building block for advanced functional p-conjugated systems

The potentialities offered by EDOT as a building block for the synthesis of functional pi-conjugated systems are reviewed. The first part underlines the specific advantages of the EDOT unit for the design of precursors of electrogenerated functional conducting polymers combining high reactivity and low polymerization potential. This topic is illustrated by some recent examples of polymers with specific electrochemical properties and/or a reduced band gap. The second part is focused on the interest of EDOT as a building block for the synthesis of various classes of molecular functional pi-conjugated systems. Examples of fluorophores, push-pull chromophores for nonlinear optics and extended pi-donors are presented. Emphasis is placed on the optical and crystallographic structure of these compounds, which shows that a major advantage of the EDOT building block lies in an unique combination of strong electron donor properties and self-structuring effects related to intramolecular non-covalent interactions between oxygen and sulfur. Such intramolecular interactions also exert a determining influence on the structure and electronic properties of pi-conjugated oligomers incorporating EDOT units which represent some of the more recent uses of the EDOT building block. The structure-property relationships of various classes of EDOT-containing conjugated oligomers are discussed in relation to their potential use as organic semi-conductors. In a brief last section, various synthetic approaches devoted to the chemistry of EDOT itself, or to the modification of its chemical structure, are discussed in relation with possible future research directions.