R. P. Shibaeva

Resistance and magnetoresistance anomaly in a new stable organic metal (ET)2TlHg(SCN)4

Abstract A new organic metal (ET) 2 TlHg(SCN) 4 has been synthesized. The X-ray study shows the compound to be isostructural to (ET) 2 MHg(SCN) 4 salts with M = K, NH 4 and Rb. The resistance and magnetoresistance measurements show anomalous behaviour at low temperature which may be attributed to spin-density-wave instability. Shubnikov-de Haas oscillations have also been observed at low temperature.

Band structure and Fermi surface of the (BEDT-TTF)4M[Fe(CN)5NO]2 (M=Na, K, Rb,…) molecular metals containing the photochromic nitroprusside anion

Abstract Tight-binding band structure calculations for the room temperature crystal structure of the new family of (BEDT-TTF)4M[Fe(CN)5NO]2 (M=Na, K, Rb, NH4, Cs, Tl) salts are reported. It is shown that the Fermi surface of these salts contains two contributions: (a) a strongly warped non-nested open part and (b) a contribution which can be open or closed depending on minor changes in the donor–donor interactions which in either case exhibits well-nested portions. Because of these features, the pressure dependence of both the magnetoresistance measurements and the possible occurrence of density wave instabilities would be very interesting to study.

Molecular metals based on radical cation salts of ET and some its analogues with the photochromic nitroprusside anion, [Fe(CN)5NO]2-

Abstract A series of electroconducting radical cation salts based on ET, BEDO and EDT with the photochromic nitroprusside anion has been synthesized. Their crystal structures and transport properties have been studied. The salts of the (ET) 4 M[Fe(CN) 5 NO] 2 (M=Na,K,NH 4 ,Tl,Rb,Cs) composition are isostructural and exhibit metallic behaviour down to helium temperatures.

Angular magnetoresistance oscillations in the organic conductor α-(ET)2KHg(SCN)4 above and below the phase transition

Abstract Angular oscillations of semi-classical magnetoresistance of α-(ET) 2 KHg(SCN) 4 have been studied at different temperatures under magnetic field rotating in various planes perpendicular to the highly-conducting ac -plane. At temperatures above the phase transition, T > T p = 8 K, the oscillations are attributed to the electron motion along the cylindrical Fermi surface sheet. In contrast, the low-temperature oscillations are shown to be associated with a specific plane arising in the electronic system below T p . The nature of the specific plane and the mechanism responsible for the low-temperature “1D” oscillations are to be clarified yet.

Novel organic superconductor κ-(ET)2Cu[N(CN)2]Cl0.5Br0.5 with Tc∼11.3 K

κ-(ET)2Cu[N(CN)2]Cl0.5Br0.5, a new organic superconductor (Tc ∼ 11.3 K at ambient pressure) has been synthesized. Its X-ray study has been undertaken.

[Ni(dddt)2]3(HSO4)2, the first metal among the M(ddt)2 salts

Abstract The first metal, [Ni(dddt)2]3(HSO4)2, among the class of M(dddt)2 cation salts has been obtained. Its structure and conducting properties have been studied. [Ni(dddt)2]3(HSO4)2 has been found to be isostructural to the (ET)3(HSO4)2 salt and their conducting properties are compared. [Ni(dddt)2]3(HSO4)2 retains its metallic state to lower temperatures (∼ 25 K) than (ET)3(HSO4)2 (∼ 130 K).

Effect of electrocrystallization medium on quality, structural features, and conducting properties of single crystals of the (BEDT-TTF)4AI[FeIII(C2O4)3]·G family

A modified procedure for the electrocrystallization of organic conductors with paramagnetic anions of the (BEDT-TTF)4AI[MIII(C2O4)3]·G family has been proposed. It is found that single crystals of different phases of the family can be prepared if the electrocrystallization medium is represented by the mixture of 1,2,4-trichlorobenzene (or 1,3-dibromobenzene), 96% ethanol and different solvents (G), only the latter being included into the composition of the resulting salts as neutral guest molecules (G = benzonitrile, fluorobenzene, chlorobenzene, 1,2-dichlorobenzene, bromobenzene, nitrobenzene). Using this approach, a number of known and new BEDT-TTF salts with the tris(oxalato)ferrate anion have been synthesized. Among them, there are superconducting crystals of monoclinic β′′-series with different guest solvents (G) and their mixtures. For the first time, crystals of a triclinic phase (G = 1,2-dibromobenzene), with alternating α- and ‘pseudo-κ’ BEDT-TTF layers and metallic behaviour down to 1.5 K, were obtained. Additionally, monoclinic crystals having another stoichiometry and α-type donor packing were prepared.

ET cation-radical salts with metal complex anions

Crystal structures and electrical properties of ET2Cu5I6, ET4[Pt(CN)4], ET4[(Pt(CN)4]C2H3Cl3, and ET3(ZnCl4)2 are described. Bond lengths and angles in ET2+ dication and ET+ cation-radical have been compared for ET3(ZnCl4)2.

New cation-radical salts of BEDT-TTF with the octahedral metal complex anions PtCl62−, PtBr62−, TeCl62− and SnCl62−. Synthesis, structure and properties

Abstract A new series of isostructural cation-radical salts of bis(ethylene)dithiotetrathiafulvalene (BEDT-TTF) with the octahedral metal complex dianions PtCl62−, PtBr62−, TeCl62− and SnCl62− have been obtained. The crystal structure of the (BEDT-TTF)4PtCl6C6H5CN salt has been determined. Although it should be attributed to the k-type of BEDT-TTF metallic salts due to the packing arrangement of the BEDT-TTF molecules, it undergoes a first-order transition into the insulating state at 250 K. Application of a pressure higher than 6 kbar results in a new conducting state. The complexes of (BEDT-TTF) with the anions PtBr62−, TeCl62− and SnCl62− exhibit semiconducting properties.

Coexistence of two donor packing motifs in the stable molecular metal α-‘pseudo-κ’-(BEDT-TTF)4(H3O)[Fe(C2O4)3]·C6H4Br2

The crystal and electronic structure of a new radical cation salt α-‘pseudo-κ’-(BEDT-TTF)4H3O[Fe(C2O4)3]·C6H4Br2 have been studied. The new triclinic crystals contain two conducting organic layers which are characterized by different BEDT-TTF packing motifs: a ‘pseudo-κ’-layer which is composed of charged dimers and neutral monomers of BEDT-TTF orthogonal to each other and an α-layer which consists of inclined, uniformly charged BEDT-TTF stacks. According to electronic band structure calculations, the ‘pseudo-κ’ layer has a large gap between the HOMO bands at the Fermi level and should be associated with an activated conductivity. In contrast, the α-layer is a strongly two-dimensional electronic system with uniform intermolecular interactions. The absence of any nesting in the Fermi surface of the α-layer suggests that this salt should be a stable metal down to low temperatures. Metallic properties have been observed in the crystals in the 300–0.4 K temperature range. Besides, well pronounced Shubnikov–de Haas oscillations of the magnetoresistance have been revealed at B > 8 T. The salt investigated is a new phase in the (BEDT-TTF)4AI[MIII(C2O4)3]G family of organic molecular conductors with paramagnetic anions and different guest solvent molecules G in the anion layer. Structural features of the new α-‘pseudo-κ’-crystals and other known phases of the family (β″, ‘pseudo-κ’ and α-β″) have been compared.