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We have measured the temperature dependences of the conductance G and the dielectric permittivity e ′ of the (TMTTF) 2 SbF 6 compound under a moderate pressure. The maximum of G ( T ) associated with the Mott–Hubbard localization disappears under pressure. With increasing pressure the peak in e ′( T ), corresponding to the charge ordering (CO) phase transition, shifts to lower temperatures and broadens. At pressures above 0.24 GPa, e ′( T ) becomes strongly frequency dependent. These modifications are explained in the frame of the extended Hubbard model and a slowing down behavior.

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.

Five new substituted tetrathiafulvalene derivatives containing the acetoxyphenyl group as a side-chain have been synthesized using a Wittig-type condensation. Four of them contain peripheral selenium atoms. From cyclic voltammetry data, the electron donor abilities of the obtained compounds have been found to be similar to that of BEDT-TTF. The crystal structures of three of these new donors have been determined. A series of radical cation salts derived from these donors has been obtained by electrocrystallization; the electrical conductivity of these phases measured on compressed powder pellets range from 5 × 10−4 to 4 × 10−5 S cm−1. Charge transfer complexes have also been chemically prepared by using TCNQ as an electron acceptor; the electrical conductivity of their compressed powders range from 0.3 to 0.5 S cm−1. The crystal structure of one of these charge transfer complexes has been determined and shows that the donor and the acceptor entities form regular segregated stacks; its rather high conductivity, actually measured on powder, is in agreement with this structural feature.

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 singly and doubly bridged bis-TTF containing a 2,6-bis(methylthio)pyridine group as a linker and potentially usable as a ligand for paramagnetic transition metal complexes is reported. Cyclisation leading to doubly bridged bis-TTF has been achieved without using the high dilution technique generally employed in such cases. The redox behaviour of such precursors has been studied by cyclic voltammetry and square wave techniques. The crystal structure of one of these electron donors has been determined by X-ray diffraction showing a stacking arrangement of the TTF units.

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.

By using a chalcogenolate (thiolate or selenolate) protection–deprotection strategy, a series of singly bridged bis-TTFs, 3a–c, 4a, have been prepared in high yield (84–96%) through two different routes. Route 2, involving the reaction between a monochalcogenolate TTF derivative with a previously prepared monoiodinated TTF species, appears to be a very useful and general strategy to selectively prepare bis-TTFs in high yields (84–90%). The bis-TTFs, 3a–c, 4a, are easily converted into the corresponding dimethylated derivatives 3a′–c′, 4a′ in a basic (2 equiv.) IMe medium. The electron-donating ability of this series of bis-TTFs has been determined by cyclic voltammetry. Several salts, mainly perchlorates, of the donors 3a, 4a, 3a′–c′ have been obtained as black powders by galvanic electrosynthesis. Their room temperature electrical conductivity as compressed powder pellets has been measured, together with the temperature dependence of the ESR signal.

Unsymmetrically substituted tetrathiafulvalene derivatives containing hydroxy group(s) on side-chain(s) have been synthesized from cyano precursors via either a cross-coupling reaction or a Wittig-type condensation. As deduced from cyclic voltammetry data, the electron donor properties of the obtained compounds have been found to be similar to those of BEDTTTF. A series of radical cation salts derived from these donors has been obtained by electrocrystallization and charge transfer complexes have been prepared chemically by using TCNQ as an electron acceptor. The electrical conductivity of these phases ranges from 3 × 10−2 to 7 × 10−7 S cm−1 which is consistent with their structural features. X-Ray structural analysis of three of the radical cation salts with monovalent closed-shell anions (Br−, ClO4−) indicates a 1 ∶ 1 stoichiometry which implies that, in each case, the donor has been oxidized to the D+ state. In the same way, a crystal structure made of stacks where the donor and the acceptor molecules alternate has been found for a charge transfer complex between TCNQ and a donor derived from EDTTTF. The crystal structure of one of the donors indicates that the flexibility of the hydroxylated side chains appears as a favourable feature for the formation of hydrogen bonds.

Preparation, crystal structures, EHT band calculations and physical properties of a semi-conducting κ-(EDS-EDT-TTF) 2 [Ag 2 (CN) 3 ] (1) and a new metallic-like species α-(BETS) 2 Ag(CN) 2 (2) are reported. κ-(EDS-EDT-TTF) 2 [Ag 2 (CN) 3 ] 1: M r =625.3, monoclinic space group P2 1 /c, a=15.157(9), b=8.732(2), c=13.51(2) A,β=90.94(3)°, V=1788 A 3 , Z=2, D c =2.324 g cm –3 , R=0.055 for 2572 reflections with F 2 ≥2σ(F 2 ). In this compound the organic molecules adopt the so-called κ type of packing. In the inorganic sublattice the [Ag 2 (CN) 3 ] – units form an infinite two-dimensional polymeric sheet. This compound shows a semi conducting behaviour, withσ 300 K =3.0×10 –4 S cm –1 and E a =120 meV. α-(BETS) 2 Ag(CN) 2 2: M r =1304.4, orthorhombic space group P2 1 2 1 2, a=9.5839(8), b=4.983(3), c=34.645(6), V=1654 A 3 , Z=2, D c =2.618 g cm –3 , R=0.057 for 1136 reflections with F 2 ≥2 σ(F 2 ). Its crystal structure consists of two-dimensional organic sheets separated by linear Ag(CN) 2 – anions. The organic molecules adopt the so-called α type of packing with a dihedral angle between two molecules belonging to two adjacent chains of ca. 78°. This compound shows metallic behaviour in the range 300-2 K, with σ 300 K =100 S cm –1 .

Radical polymerizations of methyl methacrylate were carried out in the presence of photoiniferters (RDC) containing a piperidino-dithiocarbamate group. The effects of the structure of the RDC on the photopolymerization in the presence or absence of a transfer agent such as tetraethylthiuram disulfide (TD) were investigated. The influence of the presence of a transfer agent (TD) on the living character and the control of the polymerization were also discussed.

Hall effect measurements of the organic conductor (TMTSF) 2 NO 3 at low temperatures (1.8 ≤ T ≤7 K) and high magnetic fields (H ≤ 8.5 T), are reported. The large Hall coefficient R H indicates the semimetallic nature of the spin density wave (SDW) ground state, whereas its positive sign shows the dominance of the hole carriers. Both R H and resistivity increase with decreasing temperature, which suggests the possibility that the carrier concentration is reduced as the temperature is lowered. The field variation of Hall resistance R xy deviates from the linear dependence for T ≤ 4 K and H ≥ 3 T. This could be interpreted not only by the temperature induced change in the number of carriers or anisotropy of their mobilities, but also by the possibility that the SDW state might change with the applied magnetic field.

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.

A computational (ZINDO) investigation is employed to estimate the molecular hyperpolarizability (β) of a [(TTF−NH2)8] (TTF = tetrathiafulvalene) octameric stack at various fractional (0 < ρ < 1) oxidation states of TTFρ+. While the neutral [(TTF−NH2)8] octamer exhibits a modest (7.6 × 10-30 cm5 esu-1) static β0 value, in relation to a nearly centrosymmetric electronic structure, the formal (TTF−NH2)0.25+ oxidation state leads to a giant (β0 = 3891 × 10-30 cm5 esu-1 per octamer) NLO response. This effect is related to the appearance of an extremely intense HOMO → LUMO-based low-lying transition, occurring at 1260 nm upon fractional oxidation, thus providing new and unexpected interest in TTF-donor substituted molecules. To illustrate the chemical feasibility of such species, two kinds of derivatives are synthesized: a TTF-dimethylaniline (TTF-DMA) by using in particular a Suzuki cross-coupling reaction between iodo-TTF and p-dimethylaminophenylboronic acid and a TTF-vinyldimethylaniline (TTF-VDMA) by a Wi...

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.

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.

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.

The new charge transfer complex t-TTF-TCNQ, whose unsymmetric cation is intermediate between TTF and HMTTF, presents a regular stacking of both donor and acceptor chains. We show that this compound has a metallic behavior at high temperatures and undergoes one metal-insulator transition near 81 K. Its electrical and magnetic properties are examined in connection to this phase transition and the effective dimensionality.

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.

Conductivity measurements on isotopically substituted single crystals of TTF-TCNQ show a relatively large shift in the phase transition temperatures at 52.5 K (T1) and 37.7 K (T3). Deuteration of both TTF and TCNQ chains increases T1 by 0.75 ± 0.15 K, N15 substitution increases T1 by 0.6±0.1 K while deuteration of the TTF chains apparently has no significant effect. Different possible interpretations of these results are briefly discussed.

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.

Pressure coefficients of the spin susceptibility, nuclear relaxation rates and resistivity have been measured in TTF-TCNQ, TMTTF-TCNQ and HMTSF-TCNQ. We point out that the very large pressure coefficients are not in agreement with the significantly smaller coefficients measured in optical absorption experiments under pressure. We propose an explanation of the magnetic properties of TTF-TCNQ and related compounds in terms of itinerant one dimensional antiferromagnetism. Using the Shiba-Pincus Hubbard model calculation we derive a value U/4t∥ close to unity which points towards the importance of correlations in the TTF-TCNQ family.

We report a determination of the interchain coupling via the frequency dependence of the proton spin lattice relaxation time in TTF-TCNQ. An effective value of t ⊥ ≈5.8 meV has been found. This relatively large value of interchain coupling stresses the validity of the mean field approximation for the description of the Peierls transition in TTF-TCNQ.

The synthesis, X-ray crystal structures, electron paramagnetic resonance (EPR) studies, conductivity measurements and electronic-band calculations for two new charge-transfer salts κ-(BEDO-TTF)2CF3SO3(I) and (BEDO-TTF)2CF3SO3(C4H8O)0.5(II), are described. Most of the discussion concerns the former which is the first κ-phase obtained with BEDO-TTF. This salt is metallic at room temperature (RT)(σRT= 100 S cm–1) and undergoes a slow change towards semiconducting behaviour at low temperature. Simultaneously, the EPR linewidth of the κ-phase decreases with T from ca. 60 G at 300 K, unlike the behaviour of classical κ-phase superconductors. However, the calculated band structure of I is quite similar to those previously reported for classical κ-phase salts. Comparison of magnetic and conductivity data allows the classification of κ-salts into two groups: (i) classical superconducting salts and (ii) the present salt and related materials. The properties of salts in the latter group are discussed in relation to the role of the anions.