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The thermal expansion of tetrakis (alkylthio) tetrathiafulvalenes (abbreviated to TTC n -TTFs. (n ' 1–11)) having alkyl chains with n carbon atoms has been investigated from room temperature down to about 100 K by means of the four-circle X-ray diffraction technique. A linear thermal expansion parameter δl(' δl/δT) is suggested for correlating intermolecular interaction of TTC n -TTF crystals. For the compounds with larger n, n ⩾ 8, the linear thermal expansion along the c-axis, δc, is smallest, while δ b , is larger and δ a intermediate. This is consistent with the intermolecular interaction analyses for the crystal structure of TTC a -TTF compounds. The molecular fastener effect is also found in the thermal expansion measurements. The contributions of the molecular fastener effect and the packing effect of the end C-atoms in the alkyl chains of TTC n -TTF (n '8–11) to the thermal expansion are discussed.

Electronic structures of the 2,5-dihydrothiophene derivatives were characterized by UPS spectra together with crystallographic analysis. A novel complex between the thiophene derivative and C18 TCNQ was obtained and the multilayer of the complex was prepared. Electrical conductivities with respect to the parallel and perpendicular direction to the film plane have been studied to the film structures.