Communication: The introduction of electroactivity into a self-assembled monolayer (SAM) has been attempted as a step towards a tunable interface between metals and conjugated conducting polymers. The synthesis of terthiophenes bearing an alkylthiol function at their terminal position and their chemisorption onto platinum single crystals are described. The properties of this SAM were investigated by electrochemical surface analysis and contact angle measurements. The calculation of the orientation of the terthiophene units is outlined.