J. Phys. IV France
Volume 114, April 2004
Page(s) 545 - 547

J. Phys. IV France
114 (2004) 545
DOI: 10.1051/jp4:2004114129

Crystal structure and physical properties of (EDO-TTFBr 2)2FeX 4 (X = CI, Br)

A. Miyazaki1, 1, M. Aimatsu1, H. Yamazaki1, T. Enoki1, K. Ugawa2, E. Ogura2, Y. Kuwatani2 and M. Iyoda2

1  Department of Chemistry, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8551, Japan
2  Department of Chemistry, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397, Japan

The crystal structure and physical properties of radical ion salts (EDO-TTFBr 2)2FeX 4 (X = Cl, Br) composed of halogen-substituted organic donor and magnetic halide anions are investigated. The salts consist of uniformly stacked donor molecules, whose Br substituents are connected to halide ligands of anions with remarkably short intermolecular contacts. Both salts show metallic behavior above ca. 30K. The FeCl 4 salt shows an antiferromagnetic (AF) transition at TN = 4.2K despite the absence of anion $\cdot \cdot \cdot $anion contacts, thus the magnetic interaction between the localized spins on the anions is mediated by the $\pi $-d interaction through the Br $\cdot \cdot \cdot $ Cl contacts. For the FeBr 4 salt the AF transition temperature is elevated to TN = 13.5K, accompanied with another anomaly at TC2 = 8.5K. This behavior can be qualitatively explained by a magnetic structure model where the $\pi $-d interaction between donor and anion is taken into account. Key words. Molecular conductors - molecular magnets - $\pi $-d interaction.

© EDP Sciences 2004