Bis Ethylenedithio Tetraselenafulvalene Research Articles

Electronic, non-linear optical, optoelectronic, and thermodynamic properties of undoped and doped bis (ethylenedithio) tetraselenafulvalene (BETS) (C10H8S4Se4) molecule: first study using ab initio investigation.

We have performed the ab initio calculation of the undoped and doped molecules bis (ethylenedithio) tetraselenafulvalene (BETS). Carbone (C) atoms have been substituted by Boron (B) to investigate their effects on the electronic structure and nonlinear optical, optoelectronic, and thermodynamic properties of BETS molecule. The RHF and hybrid density functional theories (WB97XD, B3PW91, and B3LYP) methods were applied, using the cc-pVDZ basis set. We found that the energy gap (Egap) of the doped molecules are respectively 2.476eV and 2.569eV for C8B2H8S4Se4 and C7B3H8S4Se4 with B3LYP/cc-pVDZ basis set, lower than one of the undoped molecule (3.316eV). The significant increase values of polarizability (˂α˃) and first order hyperpolarizability (β) of the doped compounds, especially in C8B2H8S4Se4 (< α > = 4.5315 × 10-23 esu, β = 22,672.27 × 10-33 esu and < α > = 4.518 × 10-23 esu, β = 23,657.43 × 10-33 esu respectively for B3LYP and B3PW91) compared to those of the undoped molecule (< α > = 4.3602 × 10-23 esu, β = 1290.38 × 10-33 esu, and < α > = 4.518 × 10-23 esu) show that the new molecules have a good nonlinear optical property. Results suggest that these molecules doped with boron are a potential candidate as semiconductors compounds and nonlinear optical materials.

The Peter Day Series of Magnetic (Super)Conductors

Here, we review the different series of (super)conducting and magnetic radical salts prepared with organic donors of the tetrathiafulvalene (TTF) family and oxalato-based metal complexes (ox = oxalate = C2O42−). Although most of these radical salts have been prepared with the donor bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF = ET), we also include all the salts prepared with other TTF-type donors such as tetrathiafulvalene (TTF), tetramethyl-tetrathiafulvalene (TM-TTF), bis(ethylenediseleno)tetrathiafulvalene (BEST), bis(ethylenedithio)tetraselenafulvalene (BETS) and 4,5-bis((2S)-2-hydroxypropylthio)-4′,5′-(ethylenedithio)tetrathiafulvalene (DMPET). Most of the oxalate-based complexes are monomers of the type [MIII(C2O4)3]3−, [Ge(C2O4)3]2− or [Cu(C2O4)2]2−, but we also include the reported salts with [Fe2(C2O4)5]4− dimers, [MII(H2O)2[MIII(C2O4)3]2]4− trimers and homo- or heterometallic extended 2D layers such as [MIIMIII(C2O4)3]− and [MII2(C2O4)3]2−. We will present the different structural families and their magnetic properties (such as diamagnetism, paramagnetism, antiferromagnetism, ferromagnetism and even long-range magnetic ordering) that coexist with interesting electrical properties (such as semiconductivity, metallic conductivity and even superconductivity). We will focus on the electrical and magnetic properties of the so-called Day series formulated as β″-(BEDT-TTF)4[A+MIII(C2O4)3]·G, which represents the largest family of paramagnetic metals and superconductors reported to date, with more than fifty reported examples.

Structures and Properties of New Organic Molecule-Based Metals, (D)2BrC2H4SO3 [D = BEDT-TTF and BETS

An organic anion, 2-bromoethanesulfonate (BrC2H4SO3−), provides one bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) and two bis(ethylenedithio)tetraselenafulvalene (BETS) salts, the compositions of which are β’’-β’’-(BEDT-TTF)2BrC2H4SO3 (1), β’’-β’’-(BETS)2BrC2H4SO3 (2), and θ-(BETS)2BrC2H4SO3 (3), respectively. Compound 1 shows a metal–insulator transition at around 70 K. Compound 2 is isomorphous to 1, and 3 is polymorphic with 2. Compounds 2 and 3 show metallic behavior at least down to 4.2 K. The pressure dependence of the electrical resistivity of 1 is also reported.

Structures and Properties of New Organic Conductors: BEDT-TTF, BEST and BETS Salts of the HOC2H4SO3− Anion

New bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF)-, bis(ethylenediseleno)tetrathiafulvalene (BEST)- and bis(ethylenedithio)tetraselenafulvalene (BETS)-based organic charge-transfer (CT) salts—α-(BEDT-TTF)3(HOC2H4SO3)2 (1), β-(BEST)3(HOC2H4SO3)2·H2O (2) and α-(BETS)2(HOC2H4SO3)·H2O (3)—have been prepared. Salts 1 and 2 show semiconducting behaviour. Salt 3, which is almost isostructural to α-(BETS)2I3, shows metallic behaviour down to 70 K and then shows a broader metal–insulator transition than that of α-(BETS)2I3. The reason for the difference in behaviour is estimated by the comparison of the Madelung energies of the full set of patterns of possible donor’s charge-ordered and anion’s disordered states.

Radical cation salts of BETS and ET with dicyanamidocuprate anions demonstrating metal-insulator and semiconductor–semiconductor transitions

Electrocrystallization of bis(ethylenedithio)tetraselenafulvalene (BETS) and bis(ethylenedithio)tetrathiafulvalene (ET) in the presence of an electrolyte (Ph4P)[Cu(dca)]3⋅H2O [(dca) = N(CN)2] has been studied using different solvents. A new organic metal (BETS)2Cu(dca)3 (1), and the first radical cation salt with 3D dicyanamidocuprate anion, incorporating both diamagnetic Cu1+ and paramagnetic Cu2+atoms, (ET)2Cu1.8(dca)4 (2) have been obtained. Crystal structure, conducting properties of both salts, as well as the electronic structure of 2 and its structural analog (ET)2CuMn(dca)4 (3) were analysed. The salts 1 and 2 have layered structures. In contrast to the BETS radical cation salt 1, complex 2 is characterized by the presence of a 3D polymeric anion built into the ET radical cation layers. At ambient pressure, the resistance of the crystals 1 shows semimetal behaviour down to 30 K. Below 30 K, the resistance sharply increases and the sample becomes insulating. The application of a pressure of about 3 kbar suppresses the metal-insulator transition. The salt 2 undergoes a semiconductor I - semiconductor II phase transition, which is manifested by a jump in the resistance and a hysteresis in the R(T) curves in a very large temperature range (185 – 250 K). The phase transition is accompanied by changes in the charge state of the ET molecules, and notable structure changes in the anion layer, especially in the environment of Cu2+. For the salt 3 the calculated selfconsistent charges show upon cooling a sharp increase of charge order between 291 K and 285 K.

The first BETS radical cation salts with dicyanamide anion: Crystal growth, structure and conductivity study

Electrochemical oxidation of bis(ethylenedithio)tetraselenafulvalene (BETS) has been investigated. Simple and complex dicyanamides of transition metals (Mn 2+, Ni 2+ and Fe 2+) were used as electrolytes. The correlation between composition of prepared radical cation salts and metal nature in electrolytes was established. Manganese dicyanamides provide the formation of BETS salts with the {Mn[N(CN) 2] 3}- and [N(CN) 2]-XH 2O anions. When Ni- or Fe-containing electrolytes were used only metalless BETS salts, α″-BETS 2[N(CN) 2]·2H 2O ( I) and θ-BETS 2[N(CN) 2]·3.6H 2O ( II), formed. Structures and conducting properties of these salts were analyzed. Both salts exhibit layered structure. Conducting radical cation layers have α″ (I)- or θ -type ( II). Anion sheets appear as two-dimensional polymer networks of different types. These networks are formed by [N(CN)] 2 − anions and water molecules interlinked by hydrogen bonds. Salt I is a semiconductor and II demonstrates resistance drop down to150 K at normal pressure and down to 72 K at ∼0.4 kbar pressure.

Quasi-two-dimensional organic metals with differently oriented conducting layers

New layered organic conductors based on selenium- and sulfur-containing donor molecules of bis(ethylenedithio)tetraselenafulvalene (BETS) and deuterated bis(ethylenedithio)-tetrathiafulvalene (ET) with tetrahedral anions of divalent metals of the general formula (BETS)4HgBr4(1,2-C6H4Cl2), (ET-d8)4HgBr4(C6H4Cl2) and (ET-d8)4HgBr4(C6H5X) (where X = Cl, Br) were synthesized using halobenzenes as solvents. The crystal structure of (BETS)4HgBr4(C6H4Cl2) was studied at room temperature. A distinctive feature of the crystal structures of the compounds is the alternation of the conducting layers, which differ in direction of the radical cation stacks. The conductivity along the layers is of metallic character with the temperature decrease down to 4.3 K for (BETS)4HgBr4(C6H4Cl2) and down to 40—105 K for ET-d8-based compounds, while in the direction perpendicular to the conducting layers the conductivity is semiconducting. A comparative analysis of the temperature dependence of the resistivity for the compounds (ET)4HgBr4(Solvent) (Solvent is 1,2-C6H4Cl2, C6H5X), which are based on ET and its deuterated analog, allows one to suggest that the metal—metal phase transitions observed in the 220—285 K range are of different origin: in the compounds containing 1,2-C6H4Cl2 they are due to the ordering of solvent molecules, whereas in the compounds containing C6H5X the transitions are associated with rearrangements of the terminal ethylene groups.

Two-dimensional organic metals θ-(BETS) 4MBr 4(PhBr), M = Cd, Hg with differently oriented conducting layers

New bis(ethylenedithio)tetraselenafulvalene (BETS) based radical cation salts with tetrahedral dianions [CdBr 4] 2− and [HgBr 4] 2− of the (BETS) 4MBr 4(PhBr) composition were prepared by electrochemical crystallization. Room-temperature crystal structure of (BETS) 4CdBr 4(PhBr) determined by single crystal X-ray diffraction involves BETS radical cation layers of the θ-type packing and insulating layers consisting of [CdBr 4] 2− anions and PhBr molecules. In the neighboring conducting layers, the stacks are arranged perpendicular to each other. A metal-to-metal transition within 225–230 K range was found in both (BETS) 4CdBr 4(PhBr) and (BETS) 4HgBr 4(PhBr). The behavior of electrical resistivity of these salts differs substantially along and across conducting layers. The study of magnetoresistance of (BETS) 4HgBr 4(PhBr) revealed weak Shubnikov-de Haas oscillations in fields higher than 6 T.

π-Donor BETS Based Bifunctional Superconductor with Polymeric Dicyanamidomanganate(II) Anion Layer: κ-(BETS)2Mn[N(CN)2]3

Crystals of the bis(ethylenedithio)tetraselenafulvalene (BETS) radical cation salt with dicyanamidomanganate(II) anion, kappa-(BETS)2Mn[N(CN)2]3, were synthesized, which combine conducting and magnetic properties at ambient pressure and are superconducting (Tc approximately/= 5 K) at a moderate pressure of 0.3 kbar.

Many-body effect on the superconducting transition temperature in layered organic superconductors

We have calculated bare cyclotron masses of layered organic superconductors, $\ensuremath{\kappa}$-type bis(ethylenedithio)tetrathiafulvalene (ET) and bis(ethylenedithio)tetraselenafulvalene (BETS) salts, in which the effective cyclotron masses have been determined by quantum oscillations. The higher superconducting transition temperature $({T}_{c})$ materials show the larger ratios of the observed to the bare cyclotron masses. This indicates that the mass enhancement, i.e., strong many-body effect is quite important for a high-${T}_{c}$ organic superconductor. The $\ensuremath{\kappa}$-type BETS salts need a stronger many-body interaction than the ET salts to be a superconductor, and the magnetic exchange interaction with magnetic anions realizes this requirement.

New BETS salt with the square planar [Ni(CN) 4] 2− anion

The new radical cation salt based on bis(ethylenedithio)tetraselenafulvalene (BETS) with the square planar [Ni(CN) 4] 2− anion was synthesized by electrocrystallization: (BETS) 4·Ni(CN) 4. X-ray analysis, electron transport, magnetotransport and electronic band structure calculations are presented and discussed.

BETS]2. C60complex and BETS salts with square-planar platinate (II), nickelate (II) anions: (BETS)4. Pt(CN)4, (BETS)4. Ni(CN)4

The (BETS) 2 .C 60 complex (1) and new radical cation salts based on bis(ethylenedithio)tetraselenafulvalene (BETS) with the square-planar [Ni(CN) 4 ] 2- , [Pt(CN) 4 ] 2- anions were synthesized: (BETS) 4 .Ni(CN) 4 (2), (BETS) 4 .Pt(CN) 4 (3). The crystal structure of 1 - 3 is layered. The layers consisting of C 60 molecules are alternated with the layers composed of BETS molecules in 1. The obtained complex is classified as molecular adduct in which the van der Waals interactions are predominant. The radical cation layers in the salt 2 are alternated with the anion layers along the c-direction of the unit cell. The salts retain metallic state down to 4.2 K. The band structure calculation of 2 shows 2-dimensional cylindrical Fermi surface, which is consistent with the θ- type structure and its conductivity.

Synthesis of a new donor, BEDT-HBDST and crystal structures, electrical and magnetic properties of (BEDT-HBDST) 2MX4 ( M=Fe, Ga, X=Cl, Br), where BEDT-HBDST=2,5-bis(4,5-ethylenedithio-1,3-diselenol-2-ylidene)-2,3,4,5-tetrahydrothiophene

A novel conjugation-elongated bis(ethylenedithio)tetraselenafulvalene (BETS) type donor, 2,5-bis(4,5-ethylenedithio-1,3-diselenol-2-ylidene)-2,3,4,5-tetrahydrothiophene (BEDT-HBDST) and its magnetic and non-magnetic anion salts, (BEDT-HBDST) 2 MX 4 ( MX 4 −=FeCl 4 −, GaCl 4 −, FeBr 4 − and GaBr 4 −), were prepared. These four salts are isostructural and belong to the space group of P2/ c. They showed semiconducting behavior with small activation energies (59–64 meV). The band structures of these salts are quasi one-dimensional and there is a midgap between the upper band and the lower band, since the degree of dimerization is significant in the stacking direction. The MX 4 − ions are located between the donor columns and near to the ethylenedithio moieties of the donor molecules. The magnetic susceptibilities of the FeCl 4 − and FeBr 4 − salts follow the Curie–Weiss law with Curie constants of 4.6 and 4.8 emu K mol −1 (sum of the spins of S=5/2 and S=1/2) and negative Weiss temperatures of θ=−1.2 and −4.9 K, respectively, revealing a weak antiferromagnetic interaction of 3d spins of the FeCl 4 − and FeBr 4 − anions. The Fe⋯Fe (6.66–7.60 Å), Cl⋯Cl (4.81–4.82 Å) and Br⋯Br (4.74–4.77 Å) distances in the crystal structures of these salts are significantly long. Therefore, the direct magnetic interaction between the 3d spins of the nearest neighboring Fe 3+ ions appears to be not readily accessible.

BETS-Based Molecular Conductors with Tetrahedral Anions TlCl4–, MnBr42–, CoCl42–(BETS = Bis(ethylenedithio)tetraselenafulvalene)

Molecular conductors on the basis of bis(ethylenedithio)tetraselenafulvalene (BETS) with tetrahedral anions TlCl4–, MnBr42–, and CoCl42– were synthesized and studied by X-ray diffraction analysis. The salts under study exhibit various conducting properties: κ-(BETS)2TlCl4 (I) is a superconductor with Tc = 2.5 K, θ-(BETS)4MnBr4 · 2C2H5OH (II) is a metal up to ≈30 K, while (BETS)2CoCl4 (III) is a dielectric. Salt I has κ-packing of the donor molecules, salt II has θ-packing, whereas salt III has no conducting layers. These structural differences are mainly the reasons for different conducting properties of compounds I–III.

New organic metal κ-(BETS) 4Hg 3Cl 8

New bis(ethylenedithio)tetraselenafulvalene (BETS) based radical cation salts with chloromercurate anions have been prepared by electrocrystallization. The salt (BETS) 4Hg 3Cl 8 is metallic down to 32 K, at lower temperatures the resistance grows smoothly being lower than the starting value. The salt (BETS) 4Hg 2Cl 6(C 2H 5Cl) x , x∼1, undergoes a metal-to-insulator transition near 100 K. The crystal structure of (BETS) 4Hg 3Cl 8 is formed by the layers of the BETS radical cations of the κ-type packing and inorganic layers composed of the [Hg 2Cl 6] 2− anions and the HgCl 2 molecules.

Structural and Physical Properties of New Conducting Cation Radical Salts with Te-Based Counteranions, Tetraiodotellurate(II) and Hexaiododitellurate(II)

This article reports preparation, structure, and conducting property of several cation radical salts of organic donors tetramethyltetrathiafulvalene (TMTTF), ethylenedithiotetrathiafulvalene (EDT-TTF), bis(ethylenedithio)tetrathiafulvalene (ET), bis(ethylenedithio)tetraselenafulvalene (BETS) and hexamethylenetetraselenafulvalene (HMTSF) with two novel planar Te-based dianions, TeI 4 2− and Te 2I 6 2−. (ET) 5Te 2I 6 1 and (BETS) 5Te 2I 6 2 are isostructural. In these Te 2I 6 2− salts, intermolecular short I···I contacts form a supramolecular corrugated anion sheet. Donor arrangement is similar to the θ-type. With lowering temperature, the resistivity of 1 shows a gradual increase followed by a sharp upturn at 110 K. 2 is metallic down to 120 K and shows a gradual increase of the resistivity followed by a clear transition to an insulating state around 60 K. Crystal structure of (ET) 4TeI 4 3 is based on the “herring bone” arrangement of ET molecules similar to the α-type. 3 shows a semiconductive behavior around room temperature followed by a transition to an insulating state at 210 K. (EDT-TTF) 4TeI 4 4, a semiconductor, exhibits a unique two-dimensional arrangement of dimerized EDT-TTF molecules.

Dual-action molecular superconductors with magnetic anions.

Dual-action organic superconductors, whose conducting properties can be sharply controlled by an external magnetic field, have been discovered in systems consisting of organic conduction layers based on bis(ethylenedithio)tetraselenafulvalene (BETS) molecules and magnetic anions. Owing to the metamagnetic nature of the anion layers, the superconducting state of kappa-BETS2FeBr4 can be switched on or off by applying the external field. In lambda-BETS2Fe0.4Ga0.6Cl4, exhibiting a field-induced superconducting transition for the field parallel to the conduction plane, the insulating, metallic, and superconducting states can be realized in a stepwise manner by slightly tuning the external magnetic field.

Superconductivity, Antiferromagnetism, and Phase Diagram of a Series of Organic Conductors: λ-(BETS)2FexGa1xBryCl4y

Organic conductors based on the bis(ethylenedithio)tetraselenafulvalene(BETS) are of interest because they display not only superconducting and magnetic transitions but also, as recently reported, unprecedented superconductor to insulator transitions. Here is presented the electrical and magnetic properties for two series of λ-(BETS)2FexGa1–xBryCl4–y, one system with fixed Br content, the other with fixed Fe content. This systematic study includes the superconductor to insulator transition, and also a superconductor to metal transition, which has never been previously reported for an organic conducting system.

Laser Photolysis Study on Mechanism and Efficiency of Electron Transfer Between Fullerenes (C60 and C70) and Tetraselenafulvalenes

Efficient electron-transfer reactions from three kind of tetraselenafulvalenes (TSeF's) to photoexcited triplet state of C60 or C70 in polar solvents have been confirmed by transient absorption spectroscopy observing the decay of 3C60*/3C70* and rise of C60 −•/C70 −•. Growth of single crystal seems to be stimulated by laser irradiation of the solution containing C60 and bis(ethylenedithio)tetraselena-fulvalene (BEDT-TSeF), in which C60 −• was effectively formed.

A new stable organic metal in the well known family of radical cation α-salts: α-(BETS)2TlHg(SeCN)4. Synthesis, structure and properties

The stable organic metalα-(BETS)2TlHg(SeCN)4 has been obtained by means of electrochemical oxidation of bis(ethylenedithio)tetraselenafulvalene (BETS) in 1,1,2-trichloroethane (TCE) with the addition of absolute ethanol in the presence of an electrolyte consisting of 18-crown-6, TlSeCN and Hg(SeCN)2 . The salt is isostructural with the ET-based salt with the same anion and ET and BETS salts with KHg(SCN)4 as well. The number of the side-by-side Se‥Se, Se‥S and S‥S contacts in each radical cation layer was twice that in comparison with the corresponding ET salt. Reflectivity spectra and magnetoresistance were studied. The Shubnikov–de Haas effect and angular oscillations of the magnetoresistance were observed. Optical and transport properties of α-(BETS)2TlHg(SeCN)4 were compared with those of the analogous ET salt.