scholarly journals Chiral Conducting Me-EDT-TTF and Et-EDT-TTF-Based Radical Cation Salts with the Perchlorate Anion

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1069
Author(s):  
Nabil Mroweh ◽  
Pascale Auban-Senzier ◽  
Nicolas Vanthuyne ◽  
Elsa B. Lopes ◽  
Manuel Almeida ◽  
...  
Keyword(s):  
Radical Cation ◽  
Structural Changes ◽  
Crystal Packing ◽  
Tight Binding ◽  
Molecular Conductors ◽  
Temperature Conductivity ◽  
Room Temperature Conductivity ◽  
Crystalline Materials ◽  
Metallic Conductivity ◽  
Radical Cation Salts

Introduction of chirality in the field of molecular conductors has received increasing interest in recent years in the frame of modulation of the crystal packing, and hence conducting properties, with the number of stereogenic centers and absolute configuration, e.g., racemic or enantiopure forms. Here, we describe the preparation by electrocrystallization of chiral radical cation salts, based on the donors methyl-ethylenedithio-tetrathiafulvalene (Me-EDT-TTF) 1 and ethyl-ethylenedithio-tetrathiafulvalene (Et-EDT-TTF) 2 containing one stereogenic center, with the perchlorate anion. Donor 1 provided the series of crystalline materials [(rac)-1]ClO4, [(S)-1]2ClO4 and [(R)-1]2ClO4, while for donor 2 only the 1:1 salts [(rac)-2]ClO4 and [(R)-2]ClO4 could be prepared as suitable single crystals for X-ray analysis. The enantiopure salts of 1 show β-type packing and metallic conductivity in the high temperature regime, with room temperature conductivity values of 5–10 S cm−1, whereas compound [(rac)-2]ClO4 is a very poor semiconductor. Tight-binding extended Hückel band structure calculations support the metallic conductivity of the enantiopure salts of 1 and suggest that small structural changes, possibly induced by thermal contraction or pressure, could lead to a pseudo-elliptic closed Fermi surface, typical for a 2D metal.

scholarly journals Old Donors for New Molecular Conductors: Combining TMTSF and BEDT-TTF with Anionic (TaF6)1−x/(PF6)x Alloys

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 386
Author(s):  
Magali Allain ◽  
Cécile Mézière ◽  
Pascale Auban-Senzier ◽  
Narcis Avarvari
Keyword(s):  
Single Crystal ◽  
Room Temperature ◽  
Density Wave ◽  
Spin Density Wave ◽  
Orthorhombic Phase ◽  
Molecular Conductors ◽  
Bechgaard Salts ◽  
Temperature Conductivity ◽  
Room Temperature Conductivity ◽  
Resistivity Measurements

Tetramethyl-tetraselenafulvalene (TMTSF) and bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF) are flagship precursors in the field of molecular (super)conductors. The electrocrystallization of these donors in the presence of (n-Bu4N)TaF6 or mixtures of (n-Bu4N)TaF6 and (n-Bu4N)PF6 provided Bechgaard salts formulated as (TMTSF)2(TaF6)0.84(PF6)0.16, (TMTSF)2(TaF6)0.56(PF6)0.44, (TMTSF)2(TaF6)0.44(PF6)0.56 and (TMTSF)2(TaF6)0.12(PF6)0.88, together with the monoclinic and orthorhombic phases δm-(BEDT-TTF)2(TaF6)0.94(PF6)0.06 and δo-(BEDT-TTF)2(TaF6)0.43(PF6)0.57, respectively. The use of BEDT-TTF and a mixture of (n-Bu4N)TaF6/TaF5 afforded the 1:1 phase (BEDT-TTF)2(TaF6)2·CH2Cl2. The precise Ta/P ratio in the alloys has been determined by an accurate single crystal X-ray data analysis and was corroborated with solution 19F NMR measurements. In the previously unknown crystalline phase (BEDT-TTF)2(TaF6)2·CH2Cl2 the donors organize in dimers interacting laterally yet no organic-inorganic segregation is observed. Single crystal resistivity measurements on the TMTSF based materials show typical behavior of the Bechgaard phases with room temperature conductivity σ ≈ 100 S/cm and localization below 12 K indicative of a spin density wave transition. The orthorhombic phase δo-(BEDT-TTF)2(TaF6)0.43(PF6)0.57 is semiconducting with the room temperature conductivity estimated to be σ ≈ 0.16–0.5 S/cm while the compound (BEDT-TTF)2(TaF6)2·CH2Cl2 is also a semiconductor, yet with a much lower room temperature conductivity value of 0.001 to 0.0025 S/cm, in agreement with the +1 oxidation state and strong dimerization of the donors.

scholarly journals New crystal packing arrangements in radical cation salts of BEDT-TTF with [Cr(NCS)6]3− and [Cr(NCS)5(NH3)]2−

Polyhedron ◽  
2015 ◽  
Vol 102 ◽  
pp. 75-81 ◽  
Author(s):  
Andrew C. Brooks ◽  
Lee Martin ◽  
Peter Day ◽  
William Clegg ◽  
Ross W. Harrington ◽  
...  
Keyword(s):  
Radical Cation ◽  
Crystal Packing ◽  
Radical Cation Salts

New low-dimensional molecular conductors based on bis(ethylenedithio)tetrathiafulvalene radical cation salts with octahedral metal complex anion [ReIVCl6]2–

2016 ◽  
Vol 65 (10) ◽  
pp. 2388-2395
Author(s):  
S. S. Khasanov ◽  
A. V. Kazakova ◽  
A. O. Tolstikova ◽  
S. V. Simonov ◽  
E. B. Yagubskii ◽  
...  
Keyword(s):  
Metal Complex ◽  
Radical Cation ◽  
Complex Anion ◽  
Molecular Conductors ◽  
Radical Cation Salts ◽  
Low Dimensional

scholarly journals Dihedral-Angle Dependence of Intermolecular Transfer Integrals in BEDT-BDT-Based Radical-Cation Salts with θ-Type Molecular Arrangements

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 868
Author(s):  
Tomofumi Kadoya ◽  
Shiori Sugiura ◽  
Toshiki Higashino ◽  
Keishiro Tahara ◽  
Kazuya Kubo ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Dihedral Angle ◽  
Radical Cation ◽  
Structural Phase ◽  
Tight Binding ◽  
Chain Model ◽  
Tight Binding Approximation ◽  
Highest Occupied Molecular Orbital ◽  
Radical Cation Salts ◽  
Transfer Integral

We report the structural and physical properties of a new organic Mott insulator (BEDT-BDT)AsF6 (BEDT-BDT: benzo[1,2-g:4,5-g′]bis(thieno[2,3-b][1,4dithiin). This AsF6 salt has the same structure as the PF6 salt. Although the anions are disordered, the donor molecules form a θ-type arrangement. The temperature dependence of the resistivity exhibits semiconducting behavior. The static magnetic susceptibility follows Curie–Weiss law over a wide temperature range; however, below 25 K, the magnetic susceptibility is in agreement with a one-dimensional chain model with the exchange coupling J = 7.4 K. No structural phase transition was observed down to 93 K. At 270 K, the Fermi surface calculated by the tight-binding approximation is a two-dimensional cylinder; however, it is significantly distorted at 93 K. This is because the dihedral angles between the BEDT-BDT molecules become larger due to lattice shrinkage at low temperatures, which results in a smaller transfer integral (t1) along the stack direction. This slight change in the dihedral angle gives rise to a significant change in the electronic structure of the AsF6 salt. Radical-cation salts using BEDT-BDT, in which the highest occupied molecular orbital does not have a dominant sign throughout the molecule, are sensitive to slight differences in the overlap between the molecules, and their electronic structures are more variable than those of conventional θ-type conductors.

scholarly journals Chiral Radical Cation Salts of Me-EDT-TTF and DM-EDT-TTF with Octahedral, Linear and Tetrahedral Monoanions

2021 ◽  
Vol 7 (6) ◽  
pp. 87
Author(s):  
Nabil Mroweh ◽  
Alexandra Bogdan ◽  
Flavia Pop ◽  
Pascale Auban-Senzier ◽  
Nicolas Vanthuyne ◽  
...  
Keyword(s):  
Radical Cation ◽  
Mixed Valence ◽  
Relative Location ◽  
Molecular Conductors ◽  
Resistivity Measurements ◽  
Counter Ions ◽  
Stereogenic Centers ◽  
Radical Cation Salts ◽  
Power Measurements

Methyl-ethylenedithio-tetrathiafulvalene (Me-EDT-TTF (1) and dimethyl-ethylenedithio-tetrathiafulvalene (DM-EDT-TTF (2) are valuable precursors for chiral molecular conductors, which are generally obtained by electrocrystallization in the presence of various counter-ions. The number of the stereogenic centers, their relative location on the molecule, the nature of the counter-ion and the electrocrystallization conditions play a paramount role in the crystal structures and conducting properties of the resulting materials. Here, we report the preparation and detailed structural characterization of the following series of radical cation salts: (i) mixed valence (1)2AsF6 as racemic, and (S) and (R) enantiomers; (ii) [(S)-1]AsF6·C4H8O and [(R)-1]AsF6·C4H8O where a strong dimerization of the donors is observed; (iii) (1)I3 and (2)I3 as racemic and enantiopure forms and (iv) [(meso)-2]PF6 and [(meso)-2]XO4 (X = Cl, Re), based on the new donor (meso)-2. In the latter, the two methyl substituents necessarily adopt axial and equatorial conformations, thus leading to a completely different packing of the donors when compared to the chiral form (S,S)/(R,R) of 2 in its radical cation salts. Single crystal resistivity measurements, complemented by thermoelectric power measurements in the case of (1)2AsF6, suggest quasi-metallic conductivity for the latter in the high temperature regime, with σRT ≈ 1–10 S cm–1, while semiconducting behavior is observed for the (meso)-2 based salts.

scholarly journals Contrasting crystal packing arrangements in triiodide salts of radical cations of chiral bis(pyrrolo[3,4-d])tetrathiafulvalenes

CrystEngComm ◽  
2015 ◽  
Vol 17 (38) ◽  
pp. 7354-7362 ◽  
Author(s):  
Lee Martin ◽  
Songjie Yang ◽  
Andrew C. Brooks ◽  
Peter N. Horton ◽  
Louise Male ◽  
...  
Keyword(s):  
Radical Cation ◽  
Crystal Packing ◽  
Radical Cations ◽  
Radical Cation Salts

Triiodides are arranged in head to tail pairs, infinite lines or a castellated arrangement in the radical cation salts of chiral bis(N(1-arylethyl))pyrrolo-tetrathiafulvalene salts.

New Electroconducting Radical Cation Salts Based on BEDT-TTF with 8,8’-Dibromo Cobalt Bis(Dicarbollide) Anion

2008 ◽  
Vol 54 ◽  
pp. 331-336 ◽  
Author(s):  
Olga Kazheva ◽  
Grigorii Alexandrov ◽  
Andrey Kravchenko ◽  
Vladimir Starodub ◽  
Irina Lobanova ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Electrical Conductivity ◽  
Crystal Structures ◽  
Radical Cation ◽  
Molecular Conductors ◽  
Electrical Conductivities ◽  
Radical Cation Salts

New molecular conductors on the base of 8,8’-dibromo cobalt bis(dicarbollide) anion, (BEDT-TTF)2[8,8’-Br2-3,3’-Co(1,2-C2B9H10)2] (1), and (BEDT-TTF)[8,8’-Br2-3,3’-Co(1,2-C2B9H10)2] (2) were synthesized and their crystal structures and electrical conductivities were determined. Both radical cation salts prepared were found to be semiconductors. The introduction of two bromine atoms in the cobalt bis(dicarbollide) anion produces a strong effect on crystal structure and electrical conductivity of the prepared materials.

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