Search

De Haas–van Alphen (dHvA) and Shubnikov–de Haas (SdH) oscillations of the organic metal θ -(BETS) 4 CoBr 4 (C 6 H 4 Cl 2 ) are studied in magnetic fields of up to 55 T at liquid helium temperatures. In line with Fermi surfaces (FS) illustrating the linear chain of coupled orbits, the observed Fourier components are linear combinations of the frequencies linked to the two basic orbits α and β , which have small effective masses compared to other organic metals with the same FS topology. Analytical formulas based on a second order development of the free energy within the canonical ensemble, not only account for the field and temperature dependence of the dHvA amplitudes but also for their relative values. In addition, strongly non-Lifshitz–Kosevich behaviours are quantitatively interpreted. In contrast, Shubnikov–de Haas oscillations are not accounted for by this model. [ABSTRACT FROM AUTHOR]

Properties of the spin systems of the localized 3d Mn2+ ions and the conduction π electrons in quasi-two-dimensional organic conductor κ-(BETS)2Mn[N(CN)2]3 were accessed using 1H and 13C NMR in order to find their relation to the metal-insulator transition which occurs at ∼23 K. The transition of the system into the insulating state is shown to be followed by localization of the π spins into a long-range ordered staggered structure of AF type. In contrast, the 3d Mn2+ electron spin moments form a disordered tilted structure, which may signify their trend to AF order, frustrated geometrically by the triangular arrangement of Mn in the anion layer. This result suggests that the MI transition in κ-(BETS)2Mn[N(CN)2]3 is not the consequence of the interactions within the Mn2+ spins but due to the interactions within the π-electron system itself. Vice versa, it is more likelythat the disordered tilted structure of the Mn2+ spins is induced by the ordered π-spins via the π-d interaction.

We present a study of the influence of the iodine/solvent annealing temperature on the properties of piezoresistive bilayer films with layers of α-(BEDT-TTF)2I3 [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene]. The formation of the conductive layers was tested by XRD, direct current (dc) conductivity measurements, and SEM, and the electromechanical properties have also been studied. We demonstrate that it is possible to form bilayer (BL) films with an invariant gauge factor of ca. 10 but with the temperature dependence of the resistance variable from metallic to semiconductor-like by control of the annealing temperature. This control even permits the preparation of a BL film with temperature-independent resistance. [ABSTRACT FROM AUTHOR]

We present a study of the influence of the iodine/solvent annealing temperature on the properties of piezoresistive bilayer films with layers of α-(BEDT-TTF)2I3 [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene]. The formation of the conductive layers was tested by XRD, direct current (dc) conductivity measurements, and SEM, and the electromechanical properties have also been studied. We demonstrate that it is possible to form bilayer (BL) films with an invariant gauge factor of ca. 10 but with the temperature dependence of the resistance variable from metallic to semiconductor-like by control of the annealing temperature. This control even permits the preparation of a BL film with temperature-independent resistance. [ABSTRACT FROM AUTHOR]

Highlights: [•] Magnetic torque of a multiband organic metal is measured in pulsed field up to 55T. [•] de Haas–van Alphen oscillations spectra are studied. [•] Field- and temperature-dependent amplitudes and phases are calculated. [•] Field-dependent Onsager phase factors are necessary to account for the data. [Copyright &y& Elsevier]

Abstract: Even although organic conductors have complicated crystalline structures with low symmetry and large unit cells, band structure calculations predict a multiband quasi-two-dimensional electronic structure yielding a very simple Fermi surface in most cases. Although few puzzling experimental results have been observed, data for numerous compounds are in agreement with calculations, which make them suitable systems for studying magnetic quantum oscillations in networks of orbits connected by magnetic breakdown. The state of the art of these problematics is reviewed. [Copyright &y& Elsevier]

ABSTRACT The term epigenetics was coined in the context of developmental studies, but the meaning of the term has evolved over time. Epigenetic modulators of gene expression are now known to include DNA methylation, chromatin modifications and noncoding RNAs. The observation that epigenetic changes can be transmitted transgenerationally makes the science of epigenetics very relevant to the field of environmental and molecular toxicology. Heavy metals constitute an important class of environmental contaminants that have been known to influence gene expression directly by binding various metal response elements in the target gene promoters. Recent research suggests that metals can also influence gene expression through epigenetic mechanisms; this adds a new twist to the complexity of metal-mediated gene expression. Here, we review recent studies that investigate the epigenetic, gene expression, and biological effects of various inorganic and organic forms of heavy metals, such as cadmium, arsenic, nickel, chromium, methylmercury, lead, copper and organotin compounds. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Properties of the spin systems of the localized 3d Mn2+ ions and the conduction π electrons in quasi-two-dimensional organic conductor κ-(BETS)2Mn[N(CN)2]3 were accessed using ¹H and 13C NMR in order to find their relation to the metal-insulator transition which occurs at ~23K. The transition of the system into the insulating state is shown to be followed by localization of the π spins into a long-range ordered staggered structure of AF type. In contrast, the 3d Mn2+ electron spin moments form a disordered tilted structure, which may signify their trend to AF order, frustrated geometrically by the triangular arrangement of Mn in the anion layer. This result suggests that the MI transition in κ-(BETS)2Mn[N(CN)2]3 is not the consequence of the interactions within the Mn2+ spins but due to the interactions within the π-electron system itself. Vice versa, it is more likely that the disordered tilted structure of the Mn2+ spins is induced by the ordered π-spins via the π-d interaction. [ABSTRACT FROM AUTHOR]

A simple synthesis of dialkyl (2,3-dihydro-1,3-thiazol-2-yl)-phosphonates from thiazolium salts and trialkyl phosphites is described. The series of dialkyl (2,3-dihydro-1,3-thiazol-2-yl)-phosphonates with various substituents in positions 3, 4, and 5 of the thiazole ring were prepared. However, only phosphonates with an aryl on the nitrogen atom were stable enough for chromatographic purification, although all the new phosphonates are very sensitive to oxidation. We made efforts to apply dialkyl (2,3-dihydro-1,3-thiazol-2-yl)-phosphonates in a Horner-Wadsworth-Emmons reaction, but the generated antiaromatic anion of phosphonate decomposed quickly, even at -70°C. GRAPHICAL ABSTRACT[image omitted] [ABSTRACT FROM AUTHOR]

Abstract: Magnetoresistance oscillations of the quasi-two dimensional charge transfer salt β″-(ET)4(H3O)[Fe(C2O4)3]·C6H4Cl2 are investigated in pulsed magnetic fields of up to 55T, under an applied pressure of 0.5GPa. As it is the case at ambient pressure, data are in agreement with the coexistence of a Shubnikov–de Haas orbit and a quantum interference path with the same cross section. As a result, oscillations are observed at temperatures as high as 25K. [Copyright &y& Elsevier]

Abstract: Magnetoresistance of dirty crystals of the organic metal (BEDO)5Ni(CN)4·3C2H4(OH)2 (where BEDO stands for the bis(ethylenedioxy)tetrathiafulvalene molecule) has been measured up to 54T at liquid helium temperatures. Quantum oscillations are clearly observed in a large field range even though a Dingle temperature as high as about 13K is deduced from the field dependence of the oscillations amplitude. This value corresponds to scattering time as low as ps, leading to values (where is the cyclotron pulsation) smaller than 1. Possible origins of the observed low scattering time value are discussed. [Copyright &y& Elsevier]

This report summarizes the novel features of the title complex so far investigated. (EDO-TTF) 2 PF 6 showed the first-order metal-insulator (MI) transition at 280 K, of which mechanism was assigned to the cooperated one of Peierls, charge-ordering, and order-disorder transitions. The origin of the mixing of the transition mechanisms is regarded to be the distinct molecular deformation during the phase transition. In the examination of the effect of a pulsed laser light, the insulating phase showed the ultra-fast and highly efficient photo-induced phase transition, which needed ca. 1.5 ps and one photon per ca. 500 donor molecules to produce the highly conductive metastable state. The preliminary results of the thermally induced MI transition observed in the newly obtained isostructural complexes are also mentioned. [ABSTRACT FROM AUTHOR]

Synthesis, crystal structure and physical properties of κ-(BEDO-TSeF) 2 I 3 , ( 1 ) are reported. 1 is the first example of a cation radical salt based on BEDO-TSeF, which is the latest chalcogen analogue of BEDT-TTF. [ABSTRACT FROM AUTHOR]

Hydrogen-free analogous of the bis-(ethylenedithiolo)-tetrathiafulvalene (ET) C6S8+2n, n=1, 2 and 3 (C6S10, C6S12,. C6S14) were synthesized for the first time using an original method. Thin films of conducting cation-radical salt (CRS) (C6S12)(ClO4)x were fabricated using electrochemical method. IR-spectrums and resistance measurements reveal that the CRS is organic metal-like compound which has an unusual transition near 100 K. At this temperature resistance increases about 8 times. Further decrease of temperature down to 77K leads to decrease of the resistance. [ABSTRACT FROM AUTHOR]

Hydrogen-free analogous of the bis-(ethylenedithiolo)-tetrathiafulvalene (ET) C6S8+2n, n=1, 2 and 3 (C6S10, C6S12,. C6S14) were synthesized for the first time using an original method. Thin films of conducting cation-radical salt (CRS) (C6S12)(ClO4)x were fabricated using electrochemical method. IR-spectrums and resistance measurements reveal that the CRS is organic metal-like compound which has an unusual transition near 100 K. At this temperature resistance increases about 8 times. Further decrease of temperature down to 77K leads to decrease of the resistance. [ABSTRACT FROM AUTHOR]

Spectral investigation of the new organic metal of the formula β″-(BEDT-TTF)4NH4[Cr(C2O4)3]·DMF, was performed. The polarized reflectance spectra of single crystals of the salt were recorded in the range 600–6500 cm-1, down to 4 K. Additionally, the optical absorption spectra of the powdered salt dispersed in KBr pellets, in the range 200–40,000 cm-1 were measured. The spectra are characteristic for organic metal and show small anisotropy as typical for quasi-two-dimensional materials. A Kramers–Kronig analysis of the reflectance data was performed to obtain the optical conductivity spectra. The frequency dependences of the reflectivity were fitted with a Drude model and the transport parameters were evaluated and investigated vs. temperature. [Copyright &y& Elsevier]

Using the transfer matrix method we have calculated the localization length in a 2D (two dimension) rectangular lattice with both on-site and off-diagonal disorder. Using finite size scaling we show that systems with off-diagonal disorder are much more sensitive to disorder than the system with on-site disorder, e.g. at the same amount of disorder (W=w=2) the localization length for on-site disorder is 104 times longer than for off-diagonal disorder. We consider both isotropic and anisotropic systems, where the latter can be considered as a model for an organic crystal. In the anisotropic case the maximum localization length is at the band center, the isotropic system has a maximum away from the band center. [Copyright &y& Elsevier]

The structures of organic metals (DOET)4[Hg2Cl6] ( 1) and (DOET)4[Hg2Br6] ( 2), where DOET is (1,4-dioxanediyl-2,3-dithio)ethylenedithiotetrathiafulvalene, were established by X-ray diffraction analysis. Compounds 1 and 2 are isostructural, and their crystals have layered structures. The conducting layers formed by the stacked DOET1/2+ cations alternate with the layers of the [Hg2X6]2– anions (X = Cl, Br). The temperature dependence of the conductivity of salt 1 shows a metallic character in the range of 300—4 K. Compound 2 undergoes the metal—semiconductor phase transition (TM—I) at 100 K. [ABSTRACT FROM AUTHOR]

Palladium(II)- or copper(II)-catalyzed homo-coupling reaction of either trimethylstannyltetrathiafulvalene or tetrathiafulvalenylzinc chloride produces symmetrical bitetrathiafulvalenes (bi-TTFs) in good yields, whereas palladium(0)-catalyzed cross-coupling reaction of tetrathiafulvalenylzinc chloride with 4-iodotetrathiafulvalenes leads to the corresponding unsymmetrically substituted bi-TTFs in moderate-to-high yields. The X-ray analysis of bi-TTF derivatives showed planar structures, and the cyclic voltammetry suggested that bi-TTFs have good donor ability comparable to that of BEDT-TTF. The symmetrical bi-TTFs formed the corresponding CT-complexes and cation radical salts. These CT-complexes and radical salts were found to be metallic or semiconducting, reflecting the effect of stoichiometry control in the dimeric TTF system. The X-ray structures of two cation radical salts revealed a unique stacking, and the precise conducting path in BEDO-bi-TTF·ClO4 was discussed on the basis of MO calculations. [Copyright &y& Elsevier]

Radical cation salts with halide mercurate anions were obtained by the electrochemical oxidation of bis(ethylenedioxo)tetrathiafulvalene (BEDO-TTF), and their conductivity was studied. The compounds (BEDO-TTF)HgX (X = Cl or Br), (BEDO-TTF)HgI, and (BEDO-TTF)HgBr possess the conductivity of the metallic type down to helium temperatures. [ABSTRACT FROM AUTHOR]

The compositions and structures of two new organic metals based on ET [where ET = bis(ethylenedithio)tetrathiafulvalene], viz., (ET)[Hg(SCN)Cl], with a metal-dielectric transition temperature (T) of 35°K, and (ET)[Hg(SCN)Br], with T = 140°K, were established by x-ray diffraction analysis. The crystal structures of the investigated compounds are similar to the structure of the previously studied organic metal (ET)[Hg(SCN)Cl] with T = 50°K. The principal crystallographic data for (ET)[Hg(SCN)Cl] are as follows: a = 36.64(1), b = 8.300(4), c = 11.798(1) Å, β = 89.91(3)°, V = 3588.1(9) Å, space group Cc, Z = 4, d = 2.05 g/cm. The principal crystallographic data for (ET)[Hg(SCN)Br] are as follows: a = 37.088(14), b = 8.338(3), c = 11.738(5) Å, β = 89.71(3)°, V = 3629.6(8) Å, space group C2/c, Z = 8, d = 2.15 g/cm. A characteristic feature of the crystal structure of the investigated compounds is alternation of the anion and cation layers along the a axis of the crystal. In the cation layer of the k type the ET are interconnected by shortened S...S intermolecular contacts (3.39-3.58 Å). The [Hg(SCN)X] anions (X = Cl, Br; n = 1, 2) form polymeric chains with one or two bridged SCN groups. A tendency for a decrease in the metal-dielectric transition temperature with a decrease in the volume of the anion is detected in the (ET)[Hg(SCN)X] salts, where X = Cl and Br, and n = 1 and 2. [ABSTRACT FROM AUTHOR]

The composition and structure of the radical-ion salt (ET)[Hg(SCN)Cl], a new organic metal with T=50 K, were established in an x-ray structure investigation. Principal crystallographic data: a=36.69(1), b=8.302(8), c=11.732(8) Å, β=90.02(6)°, space group Cc, Z=4, d=2.08 g/cm, R=0.067. The crystal structure of the salt consists of an alternation of organic (cationic) and inorganic (anionic) layers along the axis a. The anionic layer consists of the polymeric chains in which the [Hg(SCN)Cl] ions are linked together along the axis c through secondary Hg···N bonds with lengths of 2.75(3) and 2.98(8) Å. On account of these interactions the trigonal configuration of the bonds of the Hg atom is built up to trigonal-bipyramidal. In the organic layer with a structure of the κ type the ET cations form dimers with an interplanar distance of 3.53 Å. ET cations belonging to neighboring dimers are linked together through shortened intermolecular S...S contacts with lengths of 3.40-3.50(2) Å. [ABSTRACT FROM AUTHOR]

The electrochemical oxidation of ET [bis(ethylenedithio)tetrathiafulvalene] in bromobenzene (electrolyte BuN[HgBr]) gave the radical-cation salt (ET)[HgBr·PhBr] (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, α=118.03(3), β=89.45(2), γ=101.21(3)°, P $$\overline 1 $$ , Z=1, d=2.30 g/cm. 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 [HgBr·CHBr]. The Hg and Hg 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 and trigonal-pyramidal (tetrahedral) for Hg. Interaction between the anionic and cationic layers is effected through Br...S contacts [3.491(7) Å)]. [ABSTRACT FROM AUTHOR]

We have applied resistance fluctuation spectroscopy to study the intrinsic low-frequency dynamics of the charge carriers in the system κ -(D8-ET)2Cu[N(CN)2]Br for two different cooling rates. A strong increase of both the resistance and the noise level is observed below the thermodynamic glass-transition temperature T g. Surprisingly, the data of the normalized spectral weight 〈( δR)2〉/ R2 fall on top of each other for both cooling rates except for temperatures near the Mott critical point ( T0 ≃ 35 K) and below 28 K. The suppression of the peak in 〈( δR)2〉/ R2 associated with the Mott transition suggests that disorder is an additional parameter in the generalized phase diagram. The enhanced noise level below 28 K might be explained by a disorder-induced staggered magnetic moment in the metallic state close to the antiferromagnetic Mott insulator. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Abstract: Due to a low transition temperature and, correspondingly, a small energy gap, the charge-density-wave (CDW) state of the layered organic metal is very sensitive to pressure and magnetic field. The latter couples to the CDW via two competing mechanisms: Pauli paramagnetism and orbital motion of charge carriers in a magnetic field. We study the interplay between the Pauli and orbital effects under a pressure of 2.8kbar, in the region of the field-induced CDW (FICDW) instability. We find that, in agreement with theoretical predictions, the FICDW state is enhanced when the Zeeman splitting becomes commensurate with the orbital quantization. [Copyright &y& Elsevier]

We report high-field magnetotransport measurements on β″-BEDT-TTF4[(H3O)M(C2O4)3]C5H5N, where M=Ga3+, Cr3+ or Fe3+. In spite of the differing M ions, these compounds have very similar Fermi surfaces. We observe four distinct Shubnikov–de Haas frequencies, corresponding to four Fermi-surface pockets; the frequencies exhibit the additive relationship expected for a compensated semimetal. The compounds show paramagnetic behaviour and no superconductivity down to 0.5 K, in contrast to other materials of the same family with different solvent molecules. [Copyright &y& Elsevier]

I discuss recent measurements which allow the interlayer transfer integrals of various organic superconductors to be deduced. The measurements demonstrate the inappropriateness of criteria used to denote incoherent interlayer transport. [Copyright &y& Elsevier]

Although organic superconductors such as κ-(BEDT-TTF)2Cu(NCS)2 are in the clean limit, the superconducting transition is intrinsically broad (e.g. ∼1 K wide for Tc≈10 K). We propose that this is due to the extreme anisotropy of these materials, which greatly exacerbates the statistical effects of fluctuations. [Copyright &y& Elsevier]

Energy transport in organic materials is dependent on the coherent migration of optically induced excited states. For instance, in active organic waveguides, the tight packing of dye molecules allows delocalization of excitons over a distance generally limited to at most several hundred nanometers. Here, we demonstrate an alternative mechanism of energy transport in a triarylamine-based supramolecular organic waveguide that is plasmonic in nature and results in coherent energy propagation superior to 10 μm. The optical, electric, and magnetic properties of the doped material support the presence of metallic electrons that couple with and transport incident light. These results show that organic metals constitute a novel class of materials with efficient energy transport and are of potential interest for optoelectronics, plasmonics, and artificial light-energy harvesting systems.

Abstract: We describe how the presence of magnetic breakdown affects the appearance of angle-dependent magnetoresistance oscillations in an organic metal. The model takes account of all the contributions from quasiparticles undergoing both magnetic breakdown and Bragg reflection at each junction and allows extremely efficient simulation of data which can be compared with experimental results on . [Copyright &y& Elsevier]