Synthesis, Structure and Physical Properties of a Two-Dimensional Organic Metal, Di[bis(ethylenedithiolo)tetrathiofulvalene] triiodide, (BEDT-TTF)⁺₂I⁻₃

Abstract

Electrical oxidation of bis(ethylenedithiolo)tetrathiofulvalene (BEDT-TTF) 1 in a nitrogen saturated tetrahydrofurane solution containing (n-C4HIO)4N+I:i' as electrolyte results in the deposition of crystal plates of (BEpT-TTF)rI3' (CIOHgSshI3' These two dimensional crystals are triclinic, space group PI, a = 9.211(2), b = 1O.S50 ( 4) behave like a two dimensional metal. while below 135 K a metal-insolator transition occurs. The thermopower values indicate that the high temperature conductivity is dominated by holes. An estimate of the Fermi energy (F gives a value of (F '" 0.3 eV.

Field and frequency dependent transport in the two-dimensional organic conductor α-(BEDT-TTF)2I3

“…The nearly isotropic conductivity in the (ab)-plane is typically between 60 and 250 (f2cm)-l at room temperature; Ub/Ua ::::: 2 and Ub/Uc ::::: 4000 [2]. The compound undergoes a metal insulator transition at TMI = 135 K. A large number of studies have dealt with the nature of this phase transition [1][2][3][4][5][6][7][8][9], but very little progress has been made. The sudden opening of an energy gap was originally attributed to the formation of a charge density wave (CDW) [10].…”

“…The a phase of di-[bis(ethylenedithiolo)tetrathiofulvalene]tri-iodine was the first organic material which showed highly conducting properties in two dimensions [1]. The nearly isotropic conductivity in the (ab)-plane is typically between 60 and 250 (f2cm)-l at room temperature; Ub/Ua ::::: 2 and Ub/Uc ::::: 4000 [2].…”

C13NMR study on the charge-ordering saltα′−(

“…In contrast, ␣Ј-͑BEDT-TTF͒ 2 IBr 2 showed semiconductive behavior above and below 200 K with only activation energy showing a change at this temperature. 1,2 Although Raman spectroscopy suggested that CO was already present above 200 K, 24 NMR showed a clear CO transition at 200 K. The difference between two measurements is due to their respective time scale. Raman spectroscopy can resolve fast phenomenon, whereas NMR can resolve slower phenomenon, less than ϳ MHz.…”

“…Among these salts, the ␣ and modifications, each of which has a double column structure tilted toward each other, [1][2][3][4] have quarter-filled band structures, whereas the modification, which has strong dimeric structure, 5,6 has an approximately half-filled band structure. 7 It is important for quarter-filled systems to examine both the on-site Coulomb repulsion, U, and the off-site Coulomb repulsion, V, and these systems are likely to show charge-order ͑CO͒ state.…”

“…For ␣-͑BEDT-TTF͒ 2 I 3 , the space group is P1 and this salt consists of three crystallographically independent molecules, A, B, and C. There are inversion centers between the two A molecules, with the B and C molecules present in the inversion center. 2 This salt shows a CO transition at 135 K, leading to the opening of a magnetic gap and the system assuming a spin singlet state. 18 In contrast, -͑BEDT-TTF͒ 2 RbZn͑SCN͒ 4 has one crystallographically independent molecule in unit cell and the space group is I222.…”