Magnetoresistance effects evidencing the π-d interaction in metallic organic conductors, (EDT-DSDTFVO)2•MX4 (M = Fe, Ga; X = Cl, Br)

The 2:1 salts of a new donor molecule, EDT-DSDTFVO with MX4 - (M = Fe, Ga; X = Cl, Br) ions, were prepared. The crystal structures of the donor molecules had a β-type packing motif. All the salts essentially exhibited metallic behaviors despite the small upturns in the resistances below 30-70 K. A large negative magnetoresistance (MR) effect [-14.7% (ρ⊥) at 4.0 K and 5 T] was observed in the FeCl 4- salt, while a positive MR effect [+4.0% (ρ⊥) at 4.0 K and 5 T] was observed in the GaCl 4- salt, suggesting that there is a π-d interaction in the FeCl4- salt. The pressure application suppressed the resistivity upturns, increased the negative MR effect (-17.7% at 9.5 kbar) in the FeCl4- salt, and decreased the positive MR effect (+3.3% at 15 kbar) in the GaCl4- salt. © 2006 American Chemical Society.