A Methyl‐Substituted Thiophene–Tetra­thiafulvalene Donor and Its Salts

α-Methyldithiophene–tetrathiafulvalene (α-mDT-TTF), the first alkyl-substituted thiophene–tetrathiafulvalene electronic donor, and some of its charge-transfer salts were explored. The crystal structure of α-mDT-TTF is composed of molecular stacks aligned parallel to each other. Its cyclic voltammetry shows higher electron-donor ability than the unsubstituted analogue. This material was employed as a semiconductor in an organic field-effect transistor and showed a mobility of 4 × 10–4 cm2 V–1 s–1. Two charge-transfer salts of this donor with [M(mnt)2]– anions (mnt = maleonitriledithiolate), M = Co and Au, were obtained by electrocrystallization; they present unusual stoichiometries: (α-mDT-TTF)[Co(mnt)2] and (α-mDT-TTF)3[Au(mnt)2]2. In the cobalt compound, the donor molecules are fully oxidized and the Co complex is dimerized; it presents semiconducting behavior (7 × 10–3 S cm–1). The gold compound is composed of alternating stacks of donor trimers and pairs of anions.

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