Electrical Conductivities of Tetrakis(alkylthio)tetrathiafulvalene (TTC_n–TTF) and Tetrakis(alkyltelluro)tetrathiafulvalene (TTeC_n–TTF)

Electrical conductivities have been measured for TTCn–TTF and TTeCn–TTF. In the case of TTCn–TTF, the compounds with short alkyl chains (n=1–3) show the high resistivities above 1010 Ω cm, while the resistivities of the compounds with long alkyl chains (n≥4) decrease to 105–107 Ω cm. The relatively low resistivities of the compounds with long alkyl chains are attributed to the considerable reduction in intermolecular distance between adjacent TTF skeletons caused by intermolecular interactions through alkyl chain groups taking into account the results of their crystal structures, thermal properties and densities. As for TTeCn–TTF compounds, the carbon number dependence of resistivity is almost similar to that of TTCn–TTF in the range of large n (n≥8). Exceptionally, TTeC1–TTF exhibits noticeably low resistivity of 6.9×104 Ω cm. X-Ray diffraction study confirms that the high conductivity of TTeC1–TTF is caused by the formation of zigzag Te chains due to the presence of strong intermolecular Te–Te atomic co...