Solid-state conformation, molecular packing, and electrical and optical properties of processable beta-methylated sexithiophenes

Newly synthesized sexithiophenes, di- and tetramethylated at the P-position s, are shown to be soluble and processable compounds, giving single crystal s suitable fur X-ray structure determination. The molecular packing was cha racterized in terms of crystal cohesion and short C-H ... S and C-H ...pi i ntermolecular distances. In particular, the dimethylated sexithiophene disp layed very compressed molecular packing and a thin film field effect transi stor, fabricated with this material, was characterized by high charge mobil ity [2 x 10(-2) cm(2)/(V s)]. The tetramethylated compound crystallizes at room temperature in two different systems and with different conformations. The conformational polymorphs, which are easily interconverted at room tem perature, are characterized by different wavelengths of light emission and excitation decay rates.