MOLECULAR METALS: STRUCTURE AND PROPERTIES. O.A. Dyachenko, V.V. Gritsenko, S.V. Konovalikhin, R.N. Lyubovskaya, E.B. Yagubskii, R.B. Lyubovskii, Institute of Chemical Physics, RAS, Chernogolovka MD 142432 Russia, and E.Canadell, ICMAB, Campus de la UAB, 08193 Bellaterra, Spain

The structure-conductivity relationships were derived from crystalline diffraction experiments for the salts based on bis(ethylenedithio)tetrathiafulvalene (ET) and 5,6-dihydro-1,4-dithiin-2,3-dithiol (DDDT), which are potential electronic materials. As a subject for crystallochemical analysis were chosen the family of molecular conductors (ET)₈[Hg₄X₁₂(PhY)₂] (X=Y=Cl, metal down to 1.3 K; X=Cl, Y=Br, T_MI=10 K; X=Br, Y=Cl, T_MI=90 K; X=Y=Br, T_MI= 125 K), the first stable down to 1.3 K molecular metals, [Ni(DDDT)₂]₃(AuBr₂)₂ and [Pd(DDDT)₂]Ag_1.54Br_3.50, in the M(DDDT)₂ family of conducting complexes, as well as such relative compounds as molecular semiconductors (ET)₈[Hg₄Br₁₂(MeC₆H₄Cl)2], (ET)₈[Hg₄Cl₁₂]^.2C₆H_{6/sub>, (ET)4[Hg2I6] and investigated recently new organic metals (BEDO)4Pt(CN)4H2O and (BEDO)2Cl2H2O. In order to understand the structure-property problem in this case, we have performed a multistage crystallochemical analysis of the investigated salts by the scheme: Composition Anion and anionic layer structure Conducting layer structure (packing and overlapping types, shortened intermolecular contacts) Conductivity. On the basis of this analysis it has been established, that: i) the packing type of a conducting layer determines the conductivity type (superconductor, metal, semiconductor), and ii) there is an inverse dependence between the temperatures of metal-insulator transitions (TMI) and the densities of conducting layers. Tight-binding band structure calculations have been carried out for comparison of the electronic structures of relative molecular metals.}