A single-component molecular superconductor.

The pressure dependence of the resistivities of a single-component molecular conductor, [Ni(hfdt)2] (hfdt = bis(trifluoromethyl)tetrathiafulvalenedithiolate) with semiconducting properties at ambient pressure was examined. The four-probe resistivity measurements were performed up to ∼10 GPa using a diamond anvil cell. The low-temperature insulating phase was suppressed above 7.

Infrared electronic absorption in a single-component molecular metal.

The infrared spectra of the crystal of transition metal complex molecules with extended-TTF ligands, Ni(tmdt)2, which is the first single-component molecular metal that has a stable metallic state even at low temperatures, exhibited an extremely low-energy electronic absorption around 2200 cm-1 (tmdt = trimethylenetetrathiafulvalenedithiolate). The systematic shift of the absorption peaks for molecules similar to Ni(tmdt)2, which range from metallic to semiconducting crystals, shows that the single-component molecular conductors are composed of molecules with unprecedentedly small HOMO-LUMO gaps.