Synthesis of BEDT-TTF derivatives with carboxylic ester and amide functionalities

Synthetic routes to BEDT-TTF derivatives bearing side chain carboxylic ester and amide groups are reported. Methyl ET-ethanoate was prepared in five steps from vinylacetic acid; amide groups were installed early in the synthesis by mixed anhydride methods before the final coupling reaction.     

Polyoxometalates as Inorganic Building Blocks of Multifunctional Molecular Materials

The use of polyoxometalates (pOM's) as inorganic component in the synthesis of new molecular hybrid materials is presented. Here we show that the combination of organic molecules of the tetrathiafulvalene (TTF) type or perylene (per) with POM's yields new radical salts with unprecedented structures that present interesting magnetic and/or electrical properties or coexistence of both. The first true metallic radical salt containing a POM has been prepared and characterized. We also describe the recent results obtained by combining magnetic POM's with the organometallic cation decamethylferrocene.     

Conformation of BEDT-TTF molecules in the crystal

Based on comparison of low-temperature x-ray diffraction data for BEDT-TTF salts and quantum chemical MNDO calculations, we have shown that the most energetically favorable conformation of the BEDT-TTF molecule is not realized in the crystal. A local energy minimum 0.035 eV above the ground state corresponds to the conformation detected in the crystal. The x-ray diffraction data and the MNDO results suggest weak participation of the heteroatoms of the six-membered rings in the conjugation with the -system of the TTF-fragment in the BEDT-TTF and BEDO-TTF molecules.Institute of Chemical Physics at Chernogolovka, Russian Academy of Sciences, Chernogolovka 142432. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 4, pp. 890–894, April, 1992.     

One Dimensional Face-to-Face Stacking of Anderson–Evans [Cr(OH)6Mo6O18]3− Polyoxometalate Anion: Synthesis, Structure, and Physical Properties of (BEDT-TTF)4[Cr(OH)6Mo6O18]⋅2H2O

The synthesis, structural and magnetic characterizations of a new charge transfer salt (BEDT-TTF)₄[Cr(OH)₆Mo₆O₁₈]2H₂O based on the planar paramagnetic Anderson–Evans polyoxometalate are reported. Structural parameters: T=293 K, triclinic (P ), a=5.9545(2) Å, b=16.3767(6) Å, c=21.8643(6) Å, =110.829(2)°, =91.262(2)°, =98.129(1)°, Z=1, R=0.0540. The crystal structure is characterized by a face-to-face stacking of the anions giving rise to a one-dimensional inorganic chain which develops along the a direction. The organic layers contain two crystallographically independent BEDT-TTF dimers that form alternating stacks along the b direction. This organic chain is perpendicular to the inorganic chains. The charges on BEDT-TTF dimers are deduced to +1.2(1) and +1.7(1) on the basis of the intramolecular bond lengths. The EPR spectrum at 2.5 K is characterized by the superposition of BEDT-TTF⁺ and [Cr^III(OH)₆Mo₆O₁₈]^3– signals. The static susceptibility can be fitted by the Curie–Weiss law down to 1.9 K and the magnetic moment at 300 K is estimated to 4.21 _B , suggesting the uncorrelated spin system with BEDT-TTF⁺ (S=1/2) and Cr^III (S=3/2) ions. This interpretion is consistent with the charge disproportionation on BEDT-TTF dimers along the stack, which is supported by the refined molecular structure and is closely related to the insulating behavior (<10^–9Scm^–1 at RT).     

Raman Spectroscopy Studies of Reorientations in Isotropic Phase of Alkoxyazoxybenzenes

Abstract

Raman spectra for isotropic phase of PAA, PAP and HOAB were recorded. Three benzene rings vibrations were chosen for quantitative analysis and the choice is discussed for different PAA deuteration. The separation of vibrational and rotational relaxation was performed. Vibrational relaxation is a dominating process, but ca. 10% of total bandshape can be attributed to rotational relaxation. Rotational correlation times τ2 were calculated for all studied substances to be of the order 10^?11 s. τ2 is connected with the rotation around the long molecular axis and supports the correlation time τ₁ received from the dielectric relaxation measurements.     

Vibrational spectra of two BEDT-TTF-based organic conductors: charge order

Infrared and Raman investigations of two phases of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) based organic conductors with the same CF₃CF₂SO₃⁻ anion: β′-(BEDT-TTF)₂CF₃CF₂SO₃ and δ′-(BEDT-TTF)₂CF₃CF₂SO₃, are shortly reviewed and compared with the most typical infrared properties of the family of (BEDT-TTF)₂RR′SO₃ organic conductors, where R = SF₅, CF₃, and R′ are CH₂, CF₂, CHF, CHFCF₂, and CH₂CF₂. The role of the molecular structur and spatial organization of the counterions is discussed. Presented at 2-nd International Conference on Functional Materials and Devices, ICFMD 2008, June 16–19, 2008, Kuala Lumpur, Malaysia     

Synthesis and reactivity of amino-substituted BEDT-TTF donors as building blocks for bifunctional materials

The first two amino-substituted BEDT-TTF derivatives, aminomethyl-ET (AMET) and aminoethyl-ET (AEET), have been prepared; the critical step in both cases was a hetero Diels-Alder reaction with 1,3-dithiole-2,4,5-trithione. AEET shows expected reactivity towards electrophiles whereas AMET will not react with aryl acid chlorides or sulfonyl chlorides, but amides of AMET can be produced by DCC coupling and mixed anhydride methods.     

Charge fluctuation,charge ordering,and zero-gap state in organic conductors

We have carried out a series of measurements of angular dependence of solid-state NMR spectrum using single crystal samples on various organic molecular conductors, in order to investigate the natures of the electronic states at low temperatures. We confirmed a charge ordered insulating state in α-(BEDT-TTF)₂I₃ and large charge disproportionation in the metallic state of this salt. In another charge ordered system, θ-(BEDT-TTF)₂RbZn(SCN)₄, we observed unusual NMR line broadening, proportional to resonance shift, in the metallic state above the transition. We found that this broadening is due to charge disproportionation, or more correctly, due to the inhomogeneity of local susceptibility at nuclear sites and analyzed its dynamics. We observed similar broadening in various organic molecular conductors as well, such as θ-(BEDT-TTF)₂CsZn(SCN)₄, an exotic Bechgaad salt, (TMTSF)₂FSO₃, and λ-type BETS salts, λ-(BETS)₂(Fe,Ga)Cl₄. We found the mechanism of CD in each system is different, respectively.     

A New Organic-Inorganic Hybrid Nanocomposite, BEDT-TTF Intercalated into Layered FePS3

A new inorganic–organic hybrid compound, Fe_0.76PS₃(BEDT-TTF)_0.48 (BEDT-TTF=bis(ethylenedithio)tetrathiafulvalene), has been synthesized by the reaction of the pre-intercalate Fe_0.90PS₃(Phen)_0.41 (phen=1,10-phenanthroline) with (BEDT-TTF)₂I_x. The powder X-ray diffraction (XRD) results show that the expansion of the lattice spacing (Δ d) is about 4.0 Å compared with the pristine FePS₃, indicating that the molecular ring plane of the guest is parallel to the layer of the host. The infrared spectrum of the intercalate shows the existence of BEDT-TTF as a guest between the interlayer region of the layered FePS₃. The room-temperature electrical conductivity of the compressed pellet of Fe_0.76PS₃(BEDT-TTF)_0.48 is about 10⁻⁷ S/cm, which is in the same order of magnitude as that of the pristine FePS₃(10⁻⁷ S/cm). The magnetic properties measured with a SQUID-magnetometer indicate that Fe_0.76PS₃(BEDT-TTF)_0.48 exhibits the paramagnetism from 120 to 300 K and Curie-Weiss Law was obeyed above 140 K, but a strong antiferromagnetic phase transition occurs at T_N of 100 K.     

An in depth study of the formation of new tetrathiafulvalene derivatives from 1,8-diketones

A detailed study of the reactions of phosphorus pentasulfide and Lawesson's reagent with a series of 4,5-bis(RCOCH₂S)-1,3-dithiole-2-thiones (R=Ph, 4-MeOC₆H₄, 4-Br C₆H₄, Me) has been carried out. These reactions lead to fusion of either an unsaturated 1,4-dithiin ring or a thiophene to the dithiole; the former in higher yield, while the latter is a significant product in the reactions with Lawesson's reagent; as well as small amounts of minor products. A mechanistic rationalization of these products is discussed in some detail. The new fused dithioles have been converted to novel series of fused TTF derivatives.