Specific Structural Disorder in an Anion Layer and Its Influence on Conducting Properties of New Crystals of the (BEDT-TTF)4A+[M3+(ox)3]G Family, Where G Is 2-Halopyridine; M Is Cr, Ga; A+ Is [K0.8(H3O)0.2]+ (original) (raw)
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Journal of Structural Chemistry, 2009
We analyze the specific features of the structure and properties of crystals that belong to the family of lowdimensional molecular conductors based on BEDT-TTF (ET) radical cation salts with [MNOX 5 ] 2-(M = Os, Ru; X = Cl, Br) mononitrosyl metal complexes as anions. It is shown that when the synthesis components are changed single crystals with , , , and -types of the conducting layers form. All radical cation salts of this family can be considered as pseudopolymorphous phases with a general formula of (ET) 4 [MNOX 5 ] 2-x G x (G is a guest solvent molecule, BN or NB). The studied crystals display a range of remarkable structural features such as conformational and charge ordering in the conducting ЕТ layers as well as commensurate and incommensurate structural modulations mainly related to the positional ordering of the components of complex anion layers.
CrystEngComm, 2011
A modified procedure for the electrocrystallization of organic conductors with paramagnetic anions of the (BEDT-TTF) 4 A I [M III (C 2 O 4 ) 3 ]$G family has been proposed. It is found that single crystals of different phases of the family can be prepared if the electrocrystallization medium is represented by the mixture of 1,2,4-trichlorobenzene (or 1,3-dibromobenzene), 96% ethanol and different solvents (G), only the latter being included into the composition of the resulting salts as neutral guest molecules (G ¼ benzonitrile, fluorobenzene, chlorobenzene, 1,2-dichlorobenzene, bromobenzene, nitrobenzene). Using this approach, a number of known and new BEDT-TTF salts with the tris(oxalato)ferrate anion have been synthesized. Among them, there are superconducting crystals of monoclinic b 00 -series with different guest solvents (G) and their mixtures. For the first time, crystals of a triclinic phase (G ¼ 1,2-dibromobenzene), with alternating aand 'pseudo-k' BEDT-TTF layers and metallic behaviour down to 1.5 K, were obtained. Additionally, monoclinic crystals having another stoichiometry and a-type donor packing were prepared.
CrystEngComm, 2012
A structural phase transition from monoclinic C2/c to triclinic P 1 symmetry has been found by X-ray diffraction in a number of single crystals of the known family of organic metals and superconductors b 00 -(BEDT-TTF) 4 H 3 O[Fe(C 2 O 4 ) 3 ]$G where G stands for halogenated benzene derivatives and their mixtures with benzonitrile. The transition occurs upon lowering the temperature at 180-230 K. Comparison of the crystal and electronic structure of the monoclinic and triclinic phases reveals details of the structural transformations in the (PhCl + PhCN)-containing superconducting b 00 -crystal, as an example. It is shown that the transition concerns mainly the anion layer and has a weak influence on the structure of the BEDT-TTF layer and, consequently, on the conducting properties of the single crystals.
Acta Crystallographica Section B Structural Science, 1990
A new organic salt, bis[3,4;3',4'-bis(ethylenedithio)-2,2',5,5'-tetrathiafulvalenium] dicyanoargentate(I) monohydrate [(BEDT-TTF)2Ag(CN)2.H20] (I), has been synthesized and its crystal structure and physical properties determined. The structure of (I) is different from those of the superconducting (fl), metallic (fl") and insulating (fl' and a') phases of anhydrous (BEDT-TTF)2X, where X is a triatomic monoanion, but is similar to the newly found superconducting salts x-(BEDT-TTF)213 and (BEDT-TTF)2Cu(NCS)2. Crystal data for (I): [C10HsS8]2[Ag(CN)2].
Studies of mixed electronic-ionic conductors in BEDT-TTF family compounds
Synthetic Metals, 1993
Some of the salts of BEDT-TTF (or ET) family namely ET2Cu516, ET3CuC14xH20 and ET3AgxI 8 are good mixed electron-group Ib ion conductors. Due to the presence of frozen disorder in anion layer none of the salts is a superconductor, though the first two remain metallic properties down to lowest temperatures. Disorder and non stoichiometry effect on electron transport properties of ET2Cu5I 6 compound have been studied. ESR studies of ET2Ou5I 6 salt show that the line width is strongly increased by the disorder.
Transport properties and phase transition of organic crystal βd′ -(BEDT-TTF)2I3
Synthetic Metals, 1989
A peculiar resistivity anomaly has been observed in a new phase of (BEDT-TTF)2I 3 first synthesized recently by Zhu et al. using a diffusion method. The structure of the new phase is similar to that of its isomer ~-(BEDT-TTF)213, with a slightly different arrangement of iodine atoms and lattice constants. But, in contrast to the H-phase, which remains metallic when the temperature decreases and finally becomes a superconductor, the new phase undergoes a metal-semiconductor transition at about 140 K. Then, after a rapid rise, the resistivity peaks at ~60 K. However, the thermopower measurement shows only a small anomaly at the phase transition. A model with two energy bands is assumed to explain these phenomena. The quite different behaviour of the new phase seems to imply that the iodine anion plays a subtle role in the determination of the properties of the material.
CrystEngComm, 2011
The crystal and electronic structure of a new radical cation salt a-'pseudo-k'-(BEDT-TTF) 4 H 3 O[Fe(C 2 O 4 ) 3 ]$C 6 H 4 Br 2 have been studied. The new triclinic crystals contain two conducting organic layers which are characterized by different BEDT-TTF packing motifs: a 'pseudo-k'-layer which is composed of charged dimers and neutral monomers of BEDT-TTF orthogonal to each other and an a-layer which consists of inclined, uniformly charged BEDT-TTF stacks. According to electronic band structure calculations, the 'pseudo-k' layer has a large gap between the HOMO bands at the Fermi level and should be associated with an activated conductivity. In contrast, the a-layer is a strongly two-dimensional electronic system with uniform intermolecular interactions. The absence of any nesting in the Fermi surface of the a-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) 4 A I [M III (C 2 O 4 ) 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 a-'pseudo-k'-crystals and other known phases of the family (b 00 , 'pseudo-k' and a-b 00 ) have been compared.
A New Organic Conductor and a Novel Structural Phase Transition in the BEDT-TTF Trihalide Family
Advanced Materials, 2000
decrease of transmission (absorption increase) appears. This decrease cannot be explained by the photodegradation effect and can be accounted for by the photoinduced reorientation of azo groups. The increase of the transmission from D (a minimum point in curve a) to E indicates that azo chromophores with their long axis oriented in the direction perpendicular to the pump polarization also become photodegraded. In curve b, a decrease of transmission after the initial fast jump is observed (see the inset of , which is attributed predominantly to the photoinduced orientation effects. After this decrease, photodegradation in the direction perpendicular to the pump polarization dominates and therefore the transmission increases. Compared to curve b, the fast decrease of the transmission from C to D in curve a is due to the fact that the concentration of the azo dye trans isomers with their orientation parallel to the p c pump polarization is higher due to the prior p k pump excitation.