Vladimir A. Starodub

Syntheses, structures, and electroconductivity of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) and bis(methylenedithio)tetrathiafulvalene (BMDT-TTF) salts with cobalt 8,8′-dichloro-3,3′-bis(1,2-dicarbollide)

Radical cation salts of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) and bis(methylenedithio)tetrathiafulvalene (BMDT-TTF) with the 8,8′-dichloro derivative of cobalt bis(1,2-dicarbollide) (BEDT-TTF)2[8,8′-Cl2-3,3′-Co(1,2-C2B9H10)2] (1) and (BMDT-TTF)4[8,8′-Cl2-3,3′-Co(1,2-C2B9H10)2] (2) were synthesized and their crystal structures and electrocon-ducting properties were determined. The synthesized radical cation salts are semiconductors with the conductivity σ293 = 1.5 and 2.0 Ohm−1 cm−1, respectively. A decrease in the size of the substituent in a series of (BEDT-TTF)2[8,8′-X2-3,3′-Co(1,2-C2B9H10)2] and (BMDT-TTF)4[8,8′-X2-3,3′-Co(1,2-C2B9H10)2] (X = I, Br, Cl) results in the compression of the anion sublattice of the crystal and compaction of the radical cation packing of the conducting layer, which, in turn, increases the conductivity of the crystals.

Synthesis, structure, and properties of a new bifunctional radical cation salt with ferracarborane anion: (BEDT-TTF)2[8,8´-Cl2-3,3´-Fe(1,2-C2B9H10)2]

A new radical cation salt of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) with iron(III) bis(1,2-dicarbollide) 8,8´-dichloro derivatives, that is (BEDT-TTF)2[8,8´-Cl2-3,3´-Fe-(1,2-C2B9H10)2], was synthesized. Its electroconducting and magnetic characteristics were studied, molecular and crystal structures were determined. The electroconductivity of crystals at room temperature was σ293 ~5 Ω–1 cm–1, which is close to the corresponding value for the salt of cobalt bis(1,2-dicarbollide) dichloro derivative and is considerably higher than the electroconductivity of a similar salt of unsubstituted iron bis(1,2-dicarbollide). The measurements of magnetic susceptibility at 2—300 K showed that this salt is paramagnetic.

New Electroconducting Radical Cation Salts Based on BEDT-TTF with 8,8’-Dibromo Cobalt Bis(Dicarbollide) Anion

New molecular conductors on the base of 8,8’-dibromo cobalt bis(dicarbollide) anion, (BEDT-TTF)2[8,8’-Br2-3,3’-Co(1,2-C2B9H10)2] (1), and (BEDT-TTF)[8,8’-Br2-3,3’-Co(1,2-C2B9H10)2] (2) were synthesized and their crystal structures and electrical conductivities were determined. Both radical cation salts prepared were found to be semiconductors. The introduction of two bromine atoms in the cobalt bis(dicarbollide) anion produces a strong effect on crystal structure and electrical conductivity of the prepared materials.

Spectral and Electrophysical Properties of Anion-Radical Salts of TCNQ and Methyl-TCNQ with N-Alkylpirazinium Cations

Anion-radical salts (ARS) of 7,7,8,8-tetracyanoquinodimethane (TCNQ) and methyl-TCNQ (MTCNQ) of composition [N-(CnH2n+1)-Pz](TCNQ)m and [N-(CnH2n+1)-Pz](MTCNQ)m, with Pz for pirazinium, n=1, 2,⋯5 and m=1, 2 have been synthesized and investigated. The IR absorption spectra of these compounds have been studied at room temperature. For single crystal and pellet samples of the synthesized salts, electric conductivity has been measured in the temperature range of 77 – 300 K, and the basic electrophysical characteristics were determined. The [N-CH3-Pz](TCNQ) compound was revealed to be an organic metal undergoing a metal-dielectric transition when cooled below 120 K, the lowest temperature which has ever been achieved for ARS of TCNQ with close-type cations. The conductivity of [N-(CnH2n+1)-Pz](MTCNQ)m salts has been found to be substantial and comparable with that of analogous TCNQ-based compounds. In this, the above compounds are noticeably distinguished from the ARS with cations based on other nitrogen-containing heterocycles. In crystals of the [N-C2H5-Pz](MTCNQ)2 salt, the existence of a highly quasi-two-dimensional conducting state is expected, despite this being atypical for TCNQ-based ARS.

Crystal structure of bis­(ethyl­enedi­thio)­tetra­thia­fulvalenium μ2-acetato-bis­[tri­bromido­rhenate(III)] 1,1,2-tri­chloro­ethane hemisolvate

The crystal structure of a binuclear monocarboxylato dirhenium(III) complex with a fulvalene derivative is reported. This compound represents a radical cation salt containing a cluster unit with rhenium–rhenium quadruple bond.

Spin-Peierls transition in genuine organic TCNQ salt with pyrazine-based cation (N-Me-2,5-di-Me-Pz)(TCNQ)2

The magnetic susceptibility measurements in the temperature range from 2 K to 300 K have been performed on a novel genuine organic TCNQ salt (N-Me-2,5-di-Me-Pz)(TCNQ)2. Based on previous study of similiar material spin-ladder like behaviour was expected. However, obtained experimental data are analyzed in terms of the Heisenberg linear chain model. Transition with spin-Peierls features occurs due to the peculiarities of crystalline structure.