Bis(ethylenethio)tetrathiafulvalene Research Articles

Evaluation of charge transfer degree in the bis(ethylenethio)tetrathiafulvalene salts by Raman spectroscopy

Raman spectroscopy studies for a series of charge-transfer salts based on the bis(ethylenethio)tetrathiafulvalene (BET-TTF) were carried out in order to analyse the charge distribution on the donor molecules in the unit cell of crystals. With the help of the density functional theory calculations for BET-TTF 0 and BET-TTF +1 molecules it was shown that the Raman spectroscopy can be applied to determine the stoichiometry in the BET-TTF salts. For salts exhibiting increase of the resistivity below ca. 100 K, the Raman spectra at variable temperature indicate that this behaviour is not related to the charge disproportionation phenomenon.

Bis(ethylenethio)tetrathiafulvalene (BET‐TTF) and Related Dissymmetrical Electron Donors: From the Molecule to Functional Molecular Materials and Devices (OFETs)

AbstractFor Abstract see ChemInform Abstract in Full Text.

Interesting transport and magnetic properties in a new family of molecular materials based on the organic donor BET-TTF and the perrhenate anionElectronic supplementary information (ESI) available: overlap modes of the radical cations of 1–3. See http://www.rsc.org/suppdata/jm/b1/b106070h/

Three completely different salts, (BET-TTF)ReO4 (1), (BET-TTF)3(ReO4)2 (2), and (BET-TTF)9(ReO4)4·2(THF) (3) are obtained by small variations in the electrocrystallization conditions of bis(ethylenethio)tetrathiafulvalene (BET-TTF) with the ReO4− ion. The crystal structures of the three salts show strong differences between them. In salt 1, the completely ionic BET-TTF stacks, running along the a direction, are not regular but are forming weak dimers. Two different radical cation layers configure salt 2 and the analysis of the bond-length of BET-TTF molecules forming layers 1 and 2 shows that the β-like layer 1 has mixed valence character, while layer 2 can be regarded as an anion-cation-anion [ReO4(BET-TTF)ReO4]− sandwich layer with completely ionised BET-TTF. Only one β-like layer that consists of two different mixed valence stacks forms salt 3. Conductivity measurements show that mixed valence salts 2 and 3 are metals with a metal-semiconductor transition around 125 K and 75 K respectively whereas the completely ionised salt 1 is, as expected, a semiconductor. The effect of high quasi-hydrostatic pressure and magnetic field on the transport properties of salt 3 has also been studied. The relationship between the crystal structure and the transport properties of all three salts has been analysed by means of tight binding band structure calculations. These calculations show that layer 1 is responsible for metallic conductivity of salt 2 whereas in layer 2 the electrons are localised. EPR data of this salt indicate that there is an appreciable interaction between delocalised electrons in layer 1 and localised magnetic moments in layer 2.

BET-TTF (bisethylenethio-tetrathiafulvalene) donor as a building block of organic metals

The structural and electronic characteristics of BET-TTF (bisethylenethio-tetrathiafulvalene) are described and the influence of such characteristics in the structural, electronic and physical properties of the derived radical ion salts will be analyzed.

Novel Dissymmetric Tetrathiafulvalenes as Precursors of Organic Metals: Synthesis, X-ray Crystal Structures, Electrochemical Properties and Study of Their Radical Cations

Two new dissymmetric π-electron donors, ethylenethioethylenedithiotetrathiafulvalene (ETEDT-TTF) and ethylenethiotetrathiafulvalene (ET-TTF), based on the combination of bis(ethylenethio)tetrathiafulvalene (BET-TTF) with bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) and tetrathiafulvalene (TTF), have been synthesized and characterized. The direct synthesis of these donors by means of the coupling of the corresponding thiones or ketones in P(OMe)3 works well only for ETEDT-TTF. For ET-TTF, an alternative route has been used, in which the bis(carboxylate) derivative, ethylenethiobis(methoxycarbonyl)tetrathiafulvalene (ETDC M-TTF), is first synthesized and then decarboxylated. The crystal packings of neutral ETEDT-TTF and ET-TTF very closely resemble those of the related symmetrical donors BEDT-TTF and TTF, respectively. In contrast, the packing of the ETDC M-TTF donor is completely different, being dictated by the hydrogen bonds formed by the carbonyl groups. The electron donor ability of the new compounds has been investigated by cyclic voltammetry: ETEDT-TTF and ET-TTF are good donors, much better than ETDC M-TTF, in accordance with the electron-withdrawing character of the methoxycarbonyl substituent. The three donors form stable radical cations that have been characterized by means of UV/Vis and EPR spectroscopy. The EPR studies indicate that there is some spin density on the external sulfur atoms, which is important for the preparation of charge transfer salts with high electronic dimensionality. Indeed, a variety of properties, from stable metals to insulators, is displayed by the charge transfer salts and complexes which have been obtained with ETEDT-TTF and ET-TTF.

Unusual transport and EPR properties of the (BET-TTF)-XF 6 salts (X=P, As)

Bis(ethylenethio)tetrathiafulvalene (BET-TTF) forms with the octahedral counterions PF 6 − and AsF 6 − charge transfer salts with different composition. We focus on three of these salts: (i) a new mixed-valence salt, (BET-TTF) x(AsF 6) y, which has metallic behaviour down to 80 K and whose EPR signal splits into two lines on cooling; (ii) two isostructural salts, (BET-TTF)(XF 6) 0.7±δ (X=P, As), which reveal three possible phase transitions as temperature decreases. Optical and transport properties, EPR studies, as well as the crystal and electronic band structures are reported and discussed.

A New Family of Molecular Metals Based on Bis(ethylenethio)tetrathiafulvalene (BET-TTF) and Octahedral Counterions

A New Family of Molecular Metals Based on Bis(ethylenethio)tetrathiafulvalene (BET-TTF) and Octahedral Counterions

Charge-transfer salts based on BET-TTF and the linear ions AuX2− (X = Br, I)

Abstract The organic π-electron donor E -bis(ethylenethio)-tetrathiafulvalene (BET-TTF) forms several charge-transfer salts with linear AuX 2 − (X = Br, I) counterions. Experimental conditions significantly affect the shape and the composition of the charge-transfer crystals. In fact, salts with different stoichiometries are obtained from each counterion. The magnetic behavior of the obtained salts have been studied by EPR spectroscopy. The EPR parameters (g, and ΔH pp ) of different mixed valence salts with the same counterion are very similar. The crystal structure of (BET-TTF)AuBr 2 has been determined by X-Ray diffraction: triclinic system, P-1, Z=1, a = 5.790(4)A, b = 7.786(3)A, c = 9.716(8)A, α = 75.11(5)°, β = 89.30(4)°, γ = 77.20(5)°, V = 395.5(5)A 3 . Single crystal electrical conductivity measurements of (BET-TTF) 2 AuBr 2 show that this salt exhibits a semiconducting behavior with a σ(300) = 1.1 Scm −1 and an energy gap of 0.14 eV.

Synthesis and characterization of the charge-transfer complex C60: (BET-TTF)

Abstract Direct reaction of C 60 with the multisulfur π-electron donor E -bis(ethylenethio)-tetrathiafulvalene (BET-TTF), in toluene or chlorobenzene, gives a new charge-transfer (C-T) complex that includes one molecule of solvent. Optical measurements of both complexes show a broad absorption around 800 nm assignable to a charge-transfer band. Both compounds are in addition EPR active.

Synthesis and physical properties of new charge transfer salts derived from E-bis(ethylenethio)tetrathiafulvalene (BET-TTF)

Abstract The synthesis, characterization and physical properties of several charge transfer salts based on the organic π-electron donor bis(ethylenethio)-tetrathiafulvalene (BET-TTF) with Br− and Cu(NCS)2− anions are reported. Experimental conditions significantly affect shape and the composition of the charge-transfer solids synthesized by electrocrystallization. In fact, salts with different stoichiometries obtained from each counterion. Mixed valence salts with Br− have two water molecules in their composition. The magnetic behavior of obtained salts has been studied by EPR spectroscopy. EPR parameters (g and ΔHpp) permit to distinguish between the different stoichiomet of a given salt.