New organic conductor (EDOEDT)(4)Hg3Br8 comprising cation layers of alpha ''- and kappa(4 x 4)-types

The (EDOEDT)(4)Hg3Br8 radical cation salt of 4,5-ethylenedioxy-4',5'-ethyle ndithiotetrathiafulvalene has been synthesized as a mixture of two crystall ine phases. Phase 1 is characterized by a semiconducting type of conductivi ty and the ESR peak-to-peak linewidth equal to 70-95 G. Phase 2 exhibits me tal-like conductivity down to 105 K and the ESR peak-to-peak linewidth of 3 5-54 G. The X-ray crystal structure analysis of phase 1 reveals three cryst allographically distinct donor molecule layers in the asymmetric part of th e unit cell, one of them being composed of the stacks and the two others ar e built of mutually perpendicular tetramers. The polarized reflectance spec tra of phase 1 are discussed. (C) 1999 Elsevier Science S.A. All rights res erved.