Tetrathiapentalene-based organic conductors

Abstract

The synthesis, structure and properties of tetrathiapentalene-based (TTP) organic conductors are reviewed. Among various TTP-type donors, bis-fused tetrathiafulvalene, 2,5-bis(1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene (BDT-TTP) and its derivatives afford many metallic radical cation salts stable down to low temperatures, regardless of the size and shape of the counter anions. Most BDT-TTP conductors have a β-type donor arrangement with almost uniform stacks. Introduction of appropriate substituents results in molecular packing that differs from the β-type. A vinylogous TTP, 2-(1,3-dithiol-2-ylidene)-5-(2-ethanediylidene-1,3-dithiole)-1,3,4,6-tetrathiapentalene (DTEDT) has yielded an organic superconductor (DTEDT) 3 Au(CN) 2 as well as metallic radical cation salts, regardless of the counter anions. (Thio)pyran analogs of TTP, namely (T)PDT-TTP and its derivatives produce molecular conductors with novel molecular arrangements. A TTP analog with reduced π-electron system 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene (BDA-TTP) has afforded several organic superconductors. Highly conducting molecular metals with unusual oxidation states (+1, +5/3 and neutral) have been developed on the basis of 2,5-bis(1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene (BDT-TTP) derivatives and analogous metal derivatives M(dt) 2 (M = Ni, Au).

Synthesis and Properties of 2-Alkylidene-1,3-dithiolo[4,5-d]-4,5-ethylenediselenotetrathiafulvalene Derivatives and Crystal Structures of Their Cation Radical Salts

“…In contrast, crystal structures of the cation radical salts are different. It is known that the ethylendithio-substituted DT-TTFs tend to afford the -type molecular conductors with non-half-filled bands [10,11], and the self-aggregating property is the key to form the κ-type molecular arrangement [35]. The self-aggregating property is associated with the moderate steric hindrance of the ethylenedithio group.…”

Chemical Modifications of BDH-TTP [2,5-Bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene]: Control of Electron Correlation

“…The BDH-TTP molecule consists of two dithiolane rings and two dithiole rings (four five-membered ring systems). Thus, BDH-TTP is geometrically preferable to the BEDT-TTF molecule, which has two dihydrodithiin rings and two dithiole rings (two six-membered and two five-membered ring systems), for forming side-by-side S· · · S contacts, because four outer sulfur atoms in the dithiolane rings of BDH-TTP do not protrude from either side of the BDH-TTP molecule: An analogous geometrical difference can be found between BEDT-TTF and BDT-TTF [bis(1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene] that is composed of four dithiole rings (four five-membered ring systems) and provides many metallic salts [37]. However, in order to control the electron correlation, the side-by-side S· · · S contacts caused by the BDH-TTP donor molecules should be reduced.…”

Humidity dependent properties of a transparent conducting film doped with BEDO‐TTF complex

“…For other films, further examinations other than the surface resistivity were not carried out since no appropriate technique was available to determine the composition of the complex in the film [13]. The transparency, however, is regarded to be originated from the molecular orientation of BEDO-TTF in the film and the colorlessness of the anion species at visible region also for the C(CN) 3 and oxalate containing films.…”

“…This feature is different from that of the element-homologous compound, BEDT-TTF (see Scheme 1), the CT complexes of which show variety of crystal and electronic structures including superconducting ones. The strong tendency to produce metallic CT complexes is also observed for BDT-TTP [3], BDH-TTP [4], and their derivatives. In these cases, the multitude of sulfur atoms with significant HOMO coefficients increases the dimensionality of the electronic structure.…”

“…In fact, the reversible elimination and regain of water molecule in the superconducting (BEDO-TTF) 2 ReO 4 (H 2 O) was suggested based on the single crystal X-ray diffraction experiments [6]. Also, we had reported the humidity dependent conducting behavior of (BEDO-TTF) 2 Br(H 2 O) 3 , while the structural feature could not be clarified due to the severe deterioration of the crystallinity under dry atmosphere [7].…”