An antiferromagnetic molecular metal based on a new bent-donor molecule.

The crystal of a (ethylenedioxytetrathiafulvalenoquinone-1,3-diselenolemethide, 1)2·FeBr4·(1,2-dichloroethane, DCE)1/2 salt obtained by electrochemical oxidation of 1 in DCE containing a supporting electrolyte, NBu4·FeBr4, exhibits metallic conductivity down to 0.45 K. The negative magnetoresistance of the electrical resistance (ρ∥) in the conducting ab-plane suggests stronger interactions between the d spins of the FeBr4- ions and the conducting π electrons than those in the FeCl4- salt of the corresponding 1,3-dithiolemethide donor molecule. The d spins order antiferromagnetically at 4.5 K, the highest temperature obtained so far in antiferromagnetic molecular metals with significant π−d interactions.