J.M. Fabre

New tris- and tetrakis-tetrathiafulvalenes containing identical or different TTF units: synthesis, redox potential and radical-cation salts

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.

Preparation of asymmetrical functionalized TTF; characterization of their charge transfer salts

Abstract 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.

TTF derivative salts with “lindquist” polyoxometallate anions

Abstract 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.

Structural and physical properties of BEDO-TTF charge-transfer salts: κ-phase with CF3SO3–

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.

Synthesis of symmetrical and asymmetrical singly bridged bis-TTFs containing sulfur and selenium atoms. A study of some of their radical cation salts

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.

Structural electronic and physical properties of (BCPTTF)2MF6(M=P,As). Occurrence of a Spin Peierls transition (Tspκ 30K).

Abstract 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.

Synthesis of new unsymmetrically tetraheterofulvalenes. Study of their radical cation salts.

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.

Structural study and electrical conductivity of salts based on functionalized TTF containing peripheral selenium atoms

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.

Radical cation salts and charge transfer complexes based on functionalized TTF derivatives

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.

Structures of 3,4-dimethyl-2,2',5,5'-tetrathiafulvalene perrhenate, (DMTTF)ReO4, and 3',4'-dimethyl-3,4-tetramethylene-2,5-dithia-2',5'-diselenafulvalene hexafluorophosphate, (CHDTDMDSF)PF6

The two compounds (DMTTF)ReO 4 (1) [DMTTF=2-(1,3-dithiol-2-ylidene)-4,5-dimethyl- 1,3-dithiole cation] and (CHDTDMDSF)PF 6 (2) [CHDTDMDSF=2-(4,5-dimethyl-1,3-diselenol-2-ylidene)-4,5,6,7-tetrahydro-1,3-benzodithiole cation] contain unsymmetrically substituted tetrathiafulvalene (TTF) derivatives. They present similar crystal structures which are characterized by alternating organic dimers and inorganic pairs of anions. The values of the central C-C bond lengths are 1.39 (1) and 1.40 (1) A for (1) and (2), respectively