A new semifluorinated tetrathiafulvalene (SFTTF) derivative was prepared and its behaviour at the air-water interface (pi-A and DELTAV-A isotherms) and in multilayer films was studied. The deposition (Y type) of such a pure SFTTF monolayer (i.e. without fatty acid) onto solid substrates was successful with a good transfer ratio. X-ray experiments and IR dichroism suggests a tilt angle (ca. 35-degrees) of the semifluorinated chains with respect to the normal of the substrate. Under an atmosphere saturated with iodine vapours, the Langmuir-Blodgett films exhibit a brown colour with a broad charge transfer band around 8500 cm-1 and a low d.c. conductivity, suggesting the formation of totally ionized TTF-type dimers. After iodination and under air exposure, iodine is rapidly lost by the films and a new charge transfer band around 3400 cm-1 appears, indicating the formation of partially ionized dimers. These changes are analysed through a reversible iodination-deiodination cycle.