Polymorphism of a New Bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) Based Molecular Conductor; Novel Transformations in Metallic BEDT-TTF Layers

Abstract

The synthesis, structure, anion composition, and physical properties of a new organic conductor (BEDT-TTF)2[(IBr2)0.2(BrICl)0.1(ICl2)0.7], where BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene, are described in detail. This molecular conductor exists as two polymorphs displaying semiconducting (β‘-phase) and metallic (β‘ ‘-phase) transport properties. Complete β‘ ‘ to β and partial β‘ ‘ to β‘ transformation have been discovered for the first time in conducting BEDT-TTF-based salts and studied by using ESR spectroscopy. Both transformations are irreversible, the β‘ ‘ → β one resulting from high-temperature solid-state reactions. The β‘ ‘- and β-phases are variable in composition.

Molecular Conductors and Superconductors Based on Trihalides of BEDT-TTF and Some of Its Analogues

“…Composition of the anions and the character of trihalide particles in these salts were established by EDX and Raman spectroscopy. 74,127 The crystal packing motif (parts g and h of Figure 2) of the isostructural ET salts with small anions ICl 2 -and BrICl -is significantly different from that of the isostructural salts 2, 6, 8, and 9 with large anions (parts a and b of Figure 2). According to the overlapping modes in the stacks (parts a and b of Figure 6), the ET molecule pairs of ′-type salts are significantly more dimerized than those of -type salts.…”

“…Consequently, β‘- (ET) 2 BrICl used in the X-ray analysis may contain a mixture of the three IBr 2 - , ICl 2 - , and BrICl - anions , The former salt in the shape of needles is formed together with its β‘ ‘ polymorph (plates) on chemical oxidation of ET in NB solution by a large excess of tetramethylammonium trihalide (Me 4 N)Br 0.5 I 1.0 Cl 1.5 containing a mixture of IBr 2 - , BrICl - , and ICl 2 - anions. The latter salt was obtained, together with β-(ET) 2 I 2.3 Cl 0.7 and β‘ ‘-(ET) 2 I 1.2 Cl 1.8 phases, by oxidation of ET with ICl in NB.…”

“…The latter salt was obtained, together with β-(ET) 2 I 2.3 Cl 0.7 and β‘ ‘-(ET) 2 I 1.2 Cl 1.8 phases, by oxidation of ET with ICl in NB. Composition of the anions and the character of trihalide particles in these salts were established by EDX and Raman spectroscopy. , …”

Theoretical investigations of the structures and electronic spectra of 2-dicyanovinyldithieno[2,3-b:3′,2′-d]thiophene (DCST) and 2-dicyanovinyldithieno[3,2-b:2′,3′-d]thiophene (DCTT)

“…Examples include the increase of critical temperatures in organic superconductors [2,3], improvement of mobility in organic field effect transistors (OFETs) [4,5], formation of neutral organic metals [6], and organic conductor-to-semiconductor phase transformations [7].…”

Direct micro-patterning of TTF-based organic conductors on flexible substrates

“…13 The patterning was realized employing a local heat source and by taking advantage of the chemistry of the organic conductors, as at high temperature the iodine forming the conducting TTF-based crystals can be partially or totally removed. 8,15 Consequently, by locally heating the film surface, the conducting areas, formed by a Institut de Cie `ncia de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, 08193 Bellaterra, Spain. E-mail: vecianaj@icmab.es; laukhina@icmab.es; Fax: We used as a heat source a 1064 nm Nd : YAG laser with a maximum output of 1 W and focused down to a micron-sized spot to heat locally the sample.…”