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International audience; The paper presents a single-crystal ESR study of a series of pristine and X-ray irradiated (TMTTF)2X salts, where TMTTF is tetramethyltetrathiafulvalene and X is either a centro-symmetrical (SbF6 and Br) or a non-centro-symmetrical (ReO4, ClO4, BF4, SCN and NO3) monovalent anion. Besides standard line-width and spin-susceptibility measurements, the analysis of the asymmetry of the ESR line shape allows to obtain simultaneous information on the electrical conductivity. This whole set of data is used to determine the charge and spin gaps related to the charge ordering (CO) and anion ordering (AO) ground states and their evolution as a function of X-ray irradiation damages. We show in particular that the sensibility of (TMTTF)2X salts to irradiation depends upon the nature of the anion X and that the CO ground state is drastically affected by irradiation damages at the difference of the AO ground state. We also present evidence of a CO transition and of a decoupling between the AO transition and the opening of a spin gap in (TMTTF)2NO3.

CETBz-TTF (4,5-bis(cyanoethylthio)benzo-tetrathiafulvalene) and CESBz-TTF (4,5-bis(cyanoethylseleno)benzo-tetrathiafulvalene) 5 have been synthesized from cyano precursor via a cross-coupling reaction. Radical salts with paramagnetic Cu(II) complex anions, such as (CETBz-TTF)2CuCl4 6 and (CESBz-TTF)2CuCl4 7 have been prepared. X-ray crystal structure and physical properties of these new compounds are presented.

Within the generic (pressure, temperature) phase diagram of (TM) 2 X compounds, we have investigated the crossover between the spin density wave and superconducting ground states by transport measurements under pressure. Superconductivity is reported for the first time in (TMTTF) 2 BF 4 below 1.38 K, in the pressure range 33.5–37.5 kbar, and coexists with the spin density wave phase, present alone at lower pressure. Differential resistance measurements support the idea of a phase segregation with the proportion of the superconducting phase (related to the measured critical current) increasing with pressure.

The synthesis of series of tris- and tetrakis-tetrathiafulvalene (TTF) has been carried out by using complementary routes involving deprotection-alkylation methods of mono or dithiolates. The electron donor ability of these new compounds has been measured by cyclic voltammetry (CV) and the square wave (SQW) technique. All the products exhibit a donating power similar to those found for TTF derivatives such as TMTTF and BEDT-TTF known to lead to conducting salts. Most of these donors have been converted by galvanostatic electrosynthesis into perchlorate and hexafluorophosphate salts. These salts have been found semi-conducting.

We present c-axis resistivity measurements performed on the organic conductors and under pressure. The aim is to probe the density of states of quasi-one dimensional compounds the high temperature properties of which are those of a Luttinger liquid. It is found that the 1-D Luttinger description breaks down below a specific pressure-dependent temperature, giving rise to a transient regime. The Fermi liquid behaviour is however restored at low temperature i.e. around 10 K, as evidenced by NMR measurements. Accordingly, two different energy scales 100 K and 10 K are required to get a fair understanding of all observed physical phenomena. Our interpretation supports the picture of a power law exponent for the correlation functions of the order of 0.25–0.30.

Transverse magnetoresistance of the organic conductor (TMTSF) 2 NO 3 has been measured at ambient pressure, in fields up to 37T and in the temperature range 2–77K. For field along the lowest conductivity axis (c∗), the magnetic field is found to increase the SDW transition temperature, in agreement with theoretical predictions for SDW phase with imperfect nesting. On the other hand, two series of quantum oscillations, with frequency of 63T and 246T respectively, are observed in the 2–10K range. Both series are connected to the SDW transition but cannot be accounted for by Shubnikov-de Haas model. Anisotropy of these oscillations is studied at 4.2K.

We show that the newly discovered phase transitions in (TMTTF)2X (X=PF6, AsF6, SbF6, ReO4) are characterised by a huge divergent peak in the low frequency dielectric constant. These phase transitions can be explained by combined effect of charge disproportionation on TMTTF molecules and the uniform shift of anions, yielding thus a macroscopic ferroelectric polarisation. Anion ordering transition, which occurs for non-centrosymmetrical anions, has a specific effect depending on the distortion vector: it destabilises the ferroelectric state in the (TMTTF)2ReO4 and brings an antiferroelectric character to the transition in (TMTTF)2SCN.

New unsymmetrically substituted tetrathia- and dithiadiselenafulvalenes of the bis-ethylenedioxy-tetrathiafulvalene (BEDO-TTF) type have been prepared and characterized. Some of their radical cation salts have also been synthesized.

We briefly remind the synthesis of a series of new dimethyltetrachalcogenofulvalenes (I) bearing one or two hydroxymethyl group(s) as substituent(s). The preparation and characterization of their radical cation salts are also reported. The electrical conductivity on compressed powder pellets and their FTIR spectra are, in some cases, given.

We describe the synthesis of a series of new unsymmetrically substituted tetraselena- and dithiadiselenafulvalenes bearing one or two functionalities such as diethylacetal, formyl or hydroxymethyl groups. The physical properties and spectroscopic data of these new π-donors are reported.

International audience; The detailed synthesis of a new series of conjugated TTF ligands with nitrogen-based aromatic heterocycle are presented. In all these molecules, trimethyl-TTF or TTF skeleton are bridged to the nitrogen aromatic ligand through a conjugated spacer such as ethenyl or phenylethenyl unit. Their electrochemical characterization as well as the crystal structure of one of these compounds is given.

6 pages; International audience; We report a preliminary study of two novel complexes combining a paramagnetic transition metal (Cu(II)) and a cyclophane-type TTF-bipyridine ligand TTF-bipy = (cis)2,7-bis(pentylsulfanyl)-3,6- [2,2-bipyridine-bis(4,4-methanediyl)bis-sulfanyl]tetrathiafulvalene. The syntheses of the complexes Cu(hfac)2(TTF-bipy) (hfac = hexafluoroacetylacetonate) and Cu(NO3)2(TTF-bipy)·H2O are reported. The results of single-crystal EPR measurements are discussed on the basis of structural features deduced from preliminary X-ray diffraction data and indicate that these neutral molecular complexes behave as isolated paramagnetic units.

We report the synthesis of a new series of dithiadiselenafulvalenes. We describe the electrical conductivity and the FTIR spectra of both their radical cation salts and their charge transfer complexes with TCNQ.

The preparations, X-ray crystals structures, optical, ESR and magnetic characterizations of new Organic-donor Inorganic -Acceptor salts are presented. The [BEDT-TFF]2M6O19 ( M = Mo ( 1 ) and W ( 2 )) present orthogonalized fully oxidized and diamagnetic organic dimers. The structure of (TPh-TTF)2W6O19 (3) shows isolated and fully oxidized organic molecules. Organic stacks made of phenyl-rings and central TTF parts are also observed in the latter compound.

This paper is a review of the electrical properties of organic materials containing unsymmetrically substituted TTF and TSF. Two series of these donors were prepared using a Wittig-type reaction with the sulfur compounds, and a cross-coupling method with their selenium analogues. Their radical-cation salts were synthesized by electrochemical oxidation and their charge-transfer complexes were obtained chemically using TCNQ and its 2,5-dimethylated derivative DMTCNQ. The crystal structures were determined by X-ray diffraction when single crystals were obtained. The electrical properties are correlated to the structural data.

International audience; By using two different routes, series of new bis- and tris-TTF, containing in their linker function(s) able to generate supplementary interactions in the resulting materials, have been prepared. The first route based on deprotection-realkylation strategy allowed to introduce alcohol and ketone functions. The second way, using acid chloride and hydroxy-TTF, allowed to include ester function in the linker. The electron-donating ability of this series of TTFs has been determined by CV and by SQW.

Interlayer magnetoresistance of the Bechgaard salt (TMTSF)$_2$NO$_3$ is investigated up to 50 teslas under pressures of a few kilobars. This compound, the Fermi surface of which is quasi two-dimensional at low temperature, is a semi metal under pressure. Nevertheless, a field-induced spin density wave is evidenced at 8.5 kbar above $\sim$ 20 T. This state is characterized by a drastically different spectrum of the quantum oscillations compared to the low pressure spin density wave state.

Two asymmetric tetrathiafulvalenes of BEDO-TTF type have been prepared: EDO-DMTTF: I and EDODT-DMDSF: II. A series of radical cation salts of I have been obtained and their electrical conductivity measured. In addition crystal structure of EDO-DMTF 2 X (X=NO 3 − ; ReO 4 − ) are now given.

We report the observation of superconductivity in the spin-Peierls Fabre salt (TMTTF)2PF6 from pressure dependent electrical transport measurements above a threshold of 4.35 GPa. The data complete the sequence of ground states of this compound in the temperature and pressure plane adducing an empirical basis to the universal character of the phase diagram of the Fabre salts and their selenide analogues, the Bechgaard salts. The structure of the phase diagram at the approach of the crossover between spin-density wave and superconducting states is compared with the results of scaling theory of the interplay between both electronic instabilities under pressure. The comparison supports the view that magnetism and superconductivity in these compounds have a common electronic origin.

Chemical modifications of 4,5-bis(cyanoethylseleno) trimethylene tetrathiafulvalene based leading to new donor molecules are described. Electrochemical study of these new TTFs has been carried out. Several of these compounds are readily oxidized to lead to stable conducting radical cations salts and charge transfer complexes.

A series of new donors based on unsymmetrical tetrachalcogenofulvalenes bearing one or two NH 2 or OH groups have been synthetized in order to help promoting extended H-bonding networks in potentially conductive compounds based on radical cation salts (RCS) and charge transfer complexes (CTC) systems. The synthesis route of these donors, designed to increase selectivity and yield, is described. Preparation, stoichiometry, electrical properties, and in some cases X-ray structure analyses of Cl - , Br - , ReO 4 - , ClO 4 - as well as TCNQ salts of these donors are presented and discussed.

The ordering of the anion in the molecular conductor salt (TMTSF) 2 NO 3 at low temperature depends on the rate of cooling and corresponds to the doubling of the a cell parameter. This order-disorder transition does not affect the crystal packing as the TMTSF chains in the ordered and in the disordered crystal structures at 12K can not be distinguished. This salt is strongly 1D at low temperature.

We report the observation of the large Hall effect in the incommensurate spin-density wave (SDW) phase of (TMTSF)2NO3 and negative magnetoresistances in the semiconducting state above and below commensurate SDW phase transition of (TMTTF)2Br.

We report on the temperature dependence of the “fast oscillation” phenomenon in quasi-one dimensional molecular conductors. Magnetoresistance and magnetization measurements to 30T in the ambient pressure spin density wave state have been taken for the X = NO 3 , PF 6 and AsF 6 members of the (TMTSF) 2 X family. Complementary data on X=AsF 6 are presented by Ulmet et al . in these proceedings. All three compounds exhibit a peak in the transverse magnetoresistances ρ xx (B//c * , I//a) and ρ yy (B//c * , I//b) and thenoscillatory components around 3K, with the oscillations vanishing at higher and lower temperatures. No magnetic moment oscillations are detected in PF 6 or AsF 6 , while only extremely weak oscillations (δm~10 −10 emu) are seen in the NO 3 salt above 25T. Also, no oscillations were observed in longitudinal magnetoresistance ρ zz (B//I//c * ) measurements performed on AsF 6 and PF 6 . Possible scenarios which have been used to explain the data include imperfect nesting at T SDW leaving behind quantizable closed orbits, and quantum interference effects arising from magnetic breakdown orbits. Another may involve a new phase transition inside the SDW state.

Introduction of cyanoethyl groups (-(CH 2 ) 2 -CN) on appropriate precursors allowed us to easily synthesize two new series of functionalized TTFs [1, 2]. Their radical cation salts and charge transfer complexes have been prepared and their electrical properties have been studied. A few crystal structures have been determined.

Three asymmetric tetrathiafulvalenes 1a , 1b and 1c , derivatives of BEDO-TTF or TMTSF and containing two hydrogen atoms, have been prepared using different strategies. Series of radical cation salts obtained from these donors are described; the results of electrical conductivity and, in certain cases, the crystal structure of these salts are presented.

In this work, we describe the synthesis of DMET analogues I and II. Both their charge transfer complexes with TCNQ and series of radical cation salts are presented. Their electrical conductivity at room temperature and, in some cases, measurements as a function of T, are reported.

We report on a low temperature study of the magnetoresistance (MR) of (TMTSF) 2 AsF 6 at ambient pressure in high magnetic fields up to 37 T. We also give a detailed behavior of the fast oscillations (FO) observed in the spin-density-wave (SDW) state of the compound with a frequency of nearly 208 T for B// c ∗ .

We studied the Fermi surface of the organic conductor (TMTSF) 2 NO 3 through the measurements of magnetic quantum oscillations. Well defined Shuvnikov-de Haas(SdH) oscillations with frequency of ca. 60T can be observed below 8K and above 6T at the ambient pressure. Under a pressure of 8kbar, different oscillations with frequency of ca. 180T is observed above 10T at 450mK. Electron structure at low temperature seems strongly modified upon application of pressure which may explain the absence of superconductivity and the field-induced spin-density waves. The angular magnetoresistance could not be fit neither by Yamaji's model nor by Lebed's.

We present preliminary data on the low temperature and high field magnetoresistance of (TMTSF)2AsF6 in its ambient pressure spin density wave state. A single series of fast oscillations having a frequency of nearly 200T is clearly observed above 15T.

Some new unsymmetrical substituted tetrathiafulvalenes have been recently prepared. The PF 6 and AsF 6 salts of this new series, based on the molecule of BenzoCycloPentyl TetraThiaFulvalene (BCPTTF), exhibit room temperature conductivities of 10 and 4 ω −1 cm −1 respectively and undergo a Spin-Peierls phase transition at a relatively high temperature (T sp κ 30K). Electrical and magnetic properties are presented and discussed in relation to the structural and electronic parameters deduced from the room-temperature crystal structures.

A new series have been prepared based on unsymmetrical molecules: Dimethyl TetramethyleneTetrathiafulvalene abbreviated in the following as DMCTTF and its selenium analog DMCTSeF. With octahedral anions, structural and physical properties are reminiscent of those already observed for other radical cation salts of 2:1 stoichoimetry. We describe briefly their most attractive results. With tetrahedral anions, new structures are found containing two types of layers of organic molecules per unit cell. We give more details on these materials in particular to describe their paramagnetic and antiferromagnetic properties.

The physical properties of several DMtTTF salts are described. Decreasing the temperature, a metallic behavior is first observed although an electronic localization becomes dominant at low temperature. ESR and antiferromagnetic resonance data are also given. We show that an antiferromagnetic ground state is generally observed at low temperature, the transition temperature being strongly dependent on the anion. These results are discussed in terms of a competition between spin Peierls and AF instabilities.