Shubnikov-de Haas oscillations spectrum of the strongly correlated quasi-2D organic metal (ET)8[Hg4Cl12(C6H5Br)2] under pressure

Pressure dependence of the Shubnikov-de Haas (SdH) oscillations spectra of the quasi-two dimensional organic metal (ET)₈[ Hg₄Cl₁₂(C₆H₅Br)₂] have been studied up to 1.1 GPa in pulsed magnetic fields of up to 54 T. According to band structure calculations, its Fermi surface can be regarded as a network of compensated orbits. The SdH spectra exhibit many Fourier components typical of such a network, most of them being forbidden in the framework of the semiclassical model. Their amplitude remains large in all the pressure range studied which likely rules out chemical potential oscillation as a dominant contribution to their origin, in agreement with recent calculations relevant to compensated Fermi liquids. In addition to a strong decrease of the magnetic breakdown field and effective masses, the latter being likely due to a reduction of the strength of electron correlations, a sizeable increase of the scattering rate is observed as the applied pressure increases. This latter point, which is at variance with data of most charge transfer salts is discussed in connection with pressure-induced features of the temperature dependence of the zero-field interlayer resistance.     

Crystal and molecular structure of organic semiconductor (ET)8[Hg4Cl12] · 2C6H6

A new organic semiconductor, (ET)₈[Hg₄C1₁₂] · 2C6H6, obtained in the ET⁺-HgCl ₃ ^– -PhF system has been studied by X-ray structural analysis. Radical cations of bis(ethylenedithio)tctrathiafulvalene (ET) in the organic layer of the structure are packed in stacks ofa-type. The average angle between the planes of ET cations from adjacent stacks is 50.1°. The anionic layer is formed by four-charge centrosymmetric [Hg₄Cl₁₂]^4– complexes and benzene solvate molecules. A comparative crystal-chemical study of the salts obtained by the reaction in the ET⁺-HgX ₃ ^– -PhY system (where X = Cl, Br, and I; Y = F, Cl, and Br) made it possible to reveal a substantial effect of the sizes of the X and Y atoms on the composition of the salts and on the structural characteristics of the layers, which are responsible for the various conductivities of these salts.Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 386–391, February, 1996     

Crystal and molecular structure of (BEDT-TTF)4Cd2I6

The new radical-cation salt (BEDT-TTF)₄Cd₂I₆ has been studied by x-ray diffraction (a=19.284(6), b=12.84(1), c=7.869 (2) Å; α=72.77(4), β=94.44(2), γ= 103.97(3)^o, space group P1, Z=1, d_calc=2.32 g/cm³). The radical cation (BEDT-TTF)^1/2+ and the Cd₂I₆ ^2? anions form organic and inorganic layers alternating along the a axis. In the organic layer, (BEDT-TTF)^1/2+ are arranged in stacks and ribbons. The radical-cations in the ribbon are packed “side to side” and are joined to one another through shortened intermolecular contacts S...S 3.346(5)-3.657(4) Å. The Cd₂I₆ ^2? anion is dimeric. The Cd atom has a distorted tetrahedral bond configuration, with bond lengths Cd-I 2.722(l)-2.886(1) Å and valence angles I-Cd-I 93.8(1)-114.1(1)°.     

Bis(ethylenedithio)tetrathiafulvalene bromide-ethylkne glycol: (BEDT-TTF)2Br·C2H4(OH)2. A new organic metal

A synthesis is reported for a new radical-cation salt (BEDT- TTF)₂Br·C₂H₄(OH)₂ having metallic electric conductance up to – 200 K. X-ray diffraction structural analysis was used to establish the existence of weak hydrogen bonds connecting the bromide ions with ethylene glycol molecules into infinite chains.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1438–1440, June, 1990.The authors thank R. B. Lyubovskii for measuring the electric conductance of a monocrystal of (I).     

Synthesis and crystal structure of an organic semiconductor (ET)4[Hg2I6]

A new cation-radical salt (ET)₄[Hg₂I₆] (1), where ET is bis(ethylenedithio)tetrathiafulvalene, has been synthesized in the system ET-HgI₃ ^–-PhCl. An X-ray study of 1 (a=41.02(5),b=23.01(1),c=8.233(2) Å,V=7772(3) ų, space groupPc2₁ b,Z=4,d _calc=2.308 g cm^–3) has established its composition, chemical formula, and the main structural features. The ET cation-radicals are packed in the conducting layer, the type of packing is ; the [Hg₂I₆]^2– anion has a dimeric structure. The temperature dependence of the conductivity of the (ET)₄[Hg₂I₆] crystals (₃₀₀=6 Ohm^–1 cm^–1) has a semiconducting character.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1240–1244, July, 1994.We thank M. G. Kaplunov for his participation in the discussion of the obtained results.This work was financially supported by the Scientific Council on the Problems of High-Temperature Superconductivity (Grant No. 90346 Metallorg) and the Russian Foundation for Basic Research (Project No. 93-02-2384).     

X-ray structure of the organic conductor (ET)8[Hg2Br6·PhBr]2

The electrochemical oxidation of ET [bis(ethylenedithio)tetrathiafulvalene] in bromobenzene (electrolyte Bu ₄ N[HgBr ₃ ]) gave the radical-cation salt (ET) ₈ [Hg ₂ Br ₆ ·PhBr] ₂ (1), a new organic metal with a temperature range of 300–125 K. At 125 K a metal—dielectric transition is observed. Crystallographic data for (1):a=19.171(6),b=12.668(4),c=17.777(6) Å, =118.03(3), =89.45(2), =101.21(3)°, P ,Z=1,d _calc=2.30 g/cm ³ . The crystal structure of (1) is laminar. In the conducting organic layer the ET radical cations are linked into bands by shortened intermolecular S···S contacts of the side-to-side type. The anionic layer consists of centrosymmetric complexes [Hg ₂ Br ₆ ·C ₆ H ₅ Br] ₂ ^4– . The Hg ¹ and Hg ² atoms are characterized by a trigonal configuration of the Hg-Br bond which is built up, on account of secondary Hg···Br interactions, into trigonal-bipyramidal for Hg ¹ and trigonal-pyramidal (tetrahedral) for Hg ² . Interaction between the anionic and cationic layers is effected through Br ⁶ ...S ⁸ contacts [3.491(7) Å)].Institute of Chemical Physics, Russian Academy of Sciences, Chernogolovka 142432. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 4, pp. 894–902, April, 1992.     

Synthesis, crystal structure and photoconductivity of the first [60]fullerene complex with metal diethyldithiocarbamate: {CuII(dedtc)2}2.C60

The first molecular complex of fullerene C60 with metal dithiocarbamate, namely, {CuII(dedtc)2}2.C60(dedtc: diethyldithiocarbamate) (1) was obtained as single crystals. Butterfly-shaped CuII(dedtc)2 molecules efficiently co-crystallized with spherical fullerene molecules to form a layered structure, in which closely packed hexagonal C60 layers alternate with the layers composed of CuII(dedtc)2 dimers. The formation of the complex with C60 changes geometry and the EPR spectrum of starting CuII(dedtc)2. Magnetic susceptibility of 1 follows the Curie-Weiss law in the 300-1.9 K range with the negative Weiss constant of -2.5 K showing a weak antiferromagnetic interaction between CuII centers in the dimers. The crystals of 1 have low dark conductivity of 10(-11) S cm-1, which is consistent with a neutral ground state of the complex. Illumination of the crystals by white light increases the photocurrent by 20-50 times. The photoconductivity spectrum of 1 has a maximum at 470 nm showing that both intermolecular charge transfer between neighboring C60 molecules and photoexcitation of CuII(dedtc)2 can contribute to photogeneration of free charge carriers. The effect of a weak magnetic field with Bo<0.5 T on the photoconductivity of 1 has been found.