An Organic Metal Derived from a Selenium Analogue of Benzothienobenzothiophene

Benzothieno[3,2-b]benzothiophene (BTBT) is an excellent organic transistor material, and its charge-transfer salt (BTBT)(2)PF6 is an organic metal that exhibits conductivity as high as 1500 S cm(-1) at room temperature. Here, we report a charge-transfer salt of the selenium analogue, benzoseleno[3,2-b]benzoselenophene (BSBS). (BSBS)(2)TaF6 is a one-dimensional metal isostructural to (BTBT)(2)PF6. The resistance jump temperature is reduced from 150 to 90 K, and the increase of the low-temperature resistivity is largely diminished. However, the spin susceptibility shows an obvious drop below 50 K, which implies that the low-temperature ground state is essentially a singlet state.