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 ◽  
...  

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.

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1069
Author(s):  
Nabil Mroweh ◽  
Pascale Auban-Senzier ◽  
Nicolas Vanthuyne ◽  
Elsa B. Lopes ◽  
Manuel Almeida ◽  
...  

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.


2021 ◽  
Vol 7 (4) ◽  
pp. 54
Author(s):  
Nataliya D. Kushch ◽  
Gennady V. Shilov ◽  
Lev I. Buravov ◽  
Eduard B. Yagubskii ◽  
Vladimir N. Zverev ◽  
...  

Three radical cation salts of BDH-TTP with the paramagnetic [ReF6]2− and diamagnetic [ReO4]− anions have been synthesized: κ-(BDH-TTP)4ReF6 (1), κ-(BDH-TTP)4ReF6·4.8H2O (2) and pseudo-κ″-(BDH-TTP)3(ReO4)2 (3). The crystal and band structures, as well as the conducting properties of the salts, have been studied. The structures of the three salts are layered and characterized by alternating κ-(1, 2) and κ″-(3) type organic radical cation layers with inorganic anion sheets. Similar to other κ-salts, the conducting layers in the crystals of 1 and 2 are formed by BDH-TTP dimers. The partial population of positions of Re atoms and disorder in the anionic layers of 1–3 are their distinctive features. Compounds 1 and 2 show the metallic character of conductivity down to low temperatures, while 3 is a semiconductor. The ac susceptibility of crystals 1 was investigated in order to test the possible slow relaxation of magnetization associated with the [ReF6]2− anion.


ChemInform ◽  
2016 ◽  
Vol 47 (11) ◽  
pp. no-no
Author(s):  
Vladimir I. Bregadze ◽  
Oleg A. Dyachenko ◽  
Olga N. Kazheva ◽  
Andrey V. Kravchenko ◽  
Igor B. Sivaev ◽  
...  

1999 ◽  
Vol 102 (1-3) ◽  
pp. 1646-1649 ◽  
Author(s):  
L. Kushch ◽  
L. Buravov ◽  
V. Tkacheva ◽  
E. Yagubskii ◽  
L. Zorina ◽  
...  

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