New Molecular Conductors Based on ETEDT-TTF Trihalides: From Single Crystals to Conducting Layers of Nanocrystals

Electrocrystallization of the novel π-electron donor (ethylenethio)(ethylenedithio)tetrathiafulvalene (ETEDT-TTF) with trihalide anions has given rise to a new family of radical cation salts with insulating properties, [ETEDT-TTF]X, and conducting properties, ETEDT-TTF]X 0.42, where X = I 3 - or I y Br 3 - y - . According to X-ray data, in the isostructural completely ionic [ETEDT-TTF]X salts, the donor radical cations are strongly dimerized, with an interplane distance of 3.310−3.317 Å, and the mixed-valence [ETEDT-TTF](I 3 ) 0.42 salt is formed by segregated radical cation and anion layers alternating along the b axis. The latter salt exhibits semiconductor behavior with a high room-temperature conductivity of 24 S·cm - 1 . The large angle between the molecular planes of the donors in neighboring stacks precludes the possible metallic behavior of this salt. Interestingly, nanocrystals of the mixed-valence salts are the conducting component of new bilayer (BL) composite films that have been generated via the ETEDT-TTF + I 2 and ETEDT-TTF + IBr chemical reactions. The structure and composition of the conducting layers of these new BL films were confirmed by X-ray, EPR, and Raman spectroscopies. Similarly to the single crystals, these composite materials exhibit semiconducting behavior with a room-temperature conductivity ranging from 0.25 to 2.5 S·cm - 1 . SEM and NIR studies of the film samples were also carried out.