The crystal structures, thin-film properties, and field-effect transistor (FET) characteristics of tetrathiafulvalene (TTF) derivatives with two phenyl groups are systematically investigated. The highest mobility, 0.11 cm(2) V(-1) s(-1), is observed in biphenyl-substituted TTF (1). The correlation between the crystal structures and the FET properties demonstrates that good transistor properties are associated with two-dimensional intermolecular interaction, which is achieved when the molecules are standing nearly perpendicular to the substrate. Since these TTF derivatives are strong electron donors, the use of a metallic charge-transfer salt (TTF)(TCNQ) as the source and drain electrodes has resulted in a considerable reduction of the off current (TCNQ: tetracyanoquinodimethane).

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Herein, the solid-state emission with good fluorescence quantum yields of N-Boc-indolylbenzothiadiazoles as a new class of fluorophores is described. Their solid-state emission covers the wide range of the visible spectrum and the emission color can be tuned easily by changing the substituents on the two heteroaromatic rings. Among these, 3-methylindolyl derivatives exhibit moreover autonomously self-recovering mechanochromic luminescence, whereby the original solid-state emission could be recovered spontaneously at room temperature after exposure to a mechanical stimulus. The emission color, as well as the recovery time for the color change could be tuned via the introduction of different substituents on the benzothiadiazole ring. We propose that the mechanism of the autonomously self-recovering mechanochromic luminescence of 3-methylindolylbenzothiadiazoles is based on a partial amorphization of the crystals upon exposure to the mechanical stimulus, followed by autonomous recovering in the form of recrystallization.

Tetrathiafulvalene-based organic semiconductor with biphenyl substituents, DBP-TTF (bis(biphenyl)tetrathiafulvalene) is used as an active layer of an organic field-effect transistor. DBP-TTF forms a good thin film on a SiO2 substrate, in which the DBP-TTF molecules are arranged almost perpendicular to the substrate. The field-effect mobility of the thin-film transistor amounts to 0.11 cm2V−1s−1.

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