Pressure Effect on the π–d Interaction in (EDT-DSDTFVSDS)2FeBr4

Electronic properties of the π–d system (EDT-DSDTFVSDS) 2 FeBr 4 are investigated under high pressure up to 6.5 GPa, where EDT-DSDTFVSDS = ethylenedithiodiselenadithiafulvalenothioquinone-1,3-diselenolemethide. In order to extract the π–d interaction, the nonmagnetic anion analogue salt (EDT-DSDTFVSDS) 2 GaBr 4 is also investigated for comparison. Both salts show metallic electrical resistivity at high temperature, but exhibit insulating behaviors in two pressure regions, in the low-pressure region, i.e., [ P 3.0 GPa) for both salts. Below 3.5 GPa, the low-pressure insulating state of the FeBr 4 salt is enhanced by the π–d interaction. Whereas, the high-pressure insulating state of the FeBr 4 salt is not enhanced above 3.5 GPa. On the other hand, the π–d interaction may affect the nonmetallic behavior of the resistance above 200 K in the FeBr 4 salt owing to the scattering of π electrons from thermally f...