Organic Field-Effect Transistor Materials Based on Cycloalkane-Capped Tetrathiapentalene Derivatives

Following the previous preparation of the cyclopentane-capped tetrathiapentalene (TTP) molecule (1), we have prepared new TTP-based organic semiconductors capped with cyclobutane (2) and cyclohexane (3) units, and investigated their crystal and thin-film structures together with the field-effect transistor (FET) characteristics. The molecule capped with cyclobutane units (2) forms a uniform stacking structure extending in different directions, leading to a three-dimensional intermolecular interaction. In the crystal of the cyclohexane- capped compound (3), the S-shaped molecules stack uniformly along the crystallographic b- and c-axes, and the estimated intermolecular interaction is two dimensional. The organic FETs (OFETs) prepared by vapor deposition show markedly different mobilities, 1.3 x 10(-2) and 0.1 cm(2) V-1 s(-1) for 2 and 3, respectively, although the electrochemical properties are almost the same. The striking difference between the FET properties is attributed to the very different crystal structures of the TTP molecules depending on the terminal groups. (C) 2010 The Japan Society of Applied Physics