SYNTHESIS, STRUCTURE AND PHYSICAL-PROPERTIES OF THE ORGANIC METAL ([H-2(8)]BEDT-TTF)4CL2.6D2O

([H-2(8)]BEDT-TTF)4Cl2.6D2O [BEDT-TTF=bis(ethylenedithio)tetrathiafulv alene] has been obtained as long black needles by electrocrystallisati on of [H-2(8)]BEDT-TTF in CH2Cl2 in the presence of [(C2H5)4N]Cl.D2O. It crystallises in the orthorhombic space group Pcca, a=32.575(2) angs trom, b=6.709(1) angstrom, c=14.854(2) angstrom, V=3246(1) angstrom3 a nd Z=2. The structure consists of twisted (dihedral angle of 29-degree s) pairs of crystallographically equivalent BEDT-TTF cations forming s tacks parallel to c with close intermolecular S ... S contacts along b , resulting in layers. A layered network of chlorine and water molecul es linked by weak hydrogen bonds alternates with the layers of organic donor molecules. The conductivity parallel to b is 40 S cm-1 at 300 K , almost constant with decreasing temperature to ca. 160 K. Below 150 K the conductivity shows a temperature-dependent activation energy, ra nging from 14 meV at 140 K to 6 meV at 10 K. It increases linearly by a factor of 3 by applying a pressure up to 24 kbar; the transition tem perature decreases from 160 to 20 K. The anisotropy of the microwave c onductivity is 0.5:240:3.6 S cm-1. The spin and static susceptibilitie s measured, respectively, by electron paramagnetic resonance (EPR) and Faraday magnetometry are temperature independent between 70 and 300 K , and obey a Curie-Weiss law below 50K with theta=-4K. The calculated band structure and Fermi surface show two-dimensional character of bot h electron and hole pockets, with the possibility of 2k(F) nesting.