Molecular conductors with differently oriented conducting layers, (EDT-TTF)3Hg2Br6 and (TMBEDT-TTF)5Hg(SCN)4-xIx

Abstract

New conducting radical cation salts (EDT TTF) 3 Hg 2 Br 6 , (TMET) 5 Hg(SCN) 4-x I x (x ≈ 0.35), and (EDT TTF) 3 Hg(SCN) 3 I 0.5 (PhCl) 0.5 were synthesized. Their conductivities, ESR and polarized reflectance spectra were studied. It was shown that the organic conductors with differently oriented conducting layers (EDT TTF) 3 Hg 2 Br 6 and (TMET) 5 Hg(SCN) 4-x I x (x ≈ 0.35) are characterized by the quasi one dimensional character of electron motion. The conductivity along and across conducting layers has a semiconductive character. It was estab lished by ESR and polarized reflectance spectroscopy that the properties of such conductors are a superposition of the properties of individual conducting layers.Molecular conductors based on radical cation salts are widely investigated in recent decades. On cooling, many of these compounds exhibit metallic properties and un dergo phase transitions into the superconducting or di electric state. 1,2 Their structures and properties strongly depend on counterions that determine the character of the radical cation salts. The mercury containing anions with the halogen, thiocyanate, and mixed type ligands with diverse compositions and structures are used as counter ions. A whole class of low dimensional molecular con ductors based on the radical cation salts with the mercury containing metal complexes as anions has arisen. 3,4The radical cation salts with the thiocyanatomercu rate anions with the composition (ET) x MHg(SCN) 4 (ET is bis(ethylenedithio)tetrathiafulvalene, M is a monovalent cation), depending on the nature of the cation M, are characterized by a wide range of electroconducting properties, from semicon ducting to superconducting ones (see Ref. 4 and refer ences cited therein). The crystals of molecular conductors with the mixed halogenothiocyanatomercurate anions (ET) 2 Hg(SCN) 3-n X n (X = F, Cl, Br, I) undergo the phase transitions of the type metal-insulator upon lowering of temperature. 3 Among the radical cation salts with the halogenomercurate anions, there are superconductors (ET) 4