Oligomeric Tetrathiafulvalenes: Extended donors for increasing the dimensionality of electrical conduction

Abstract

Novel monomeric, oligomeric, and polymeric charge‐transfer complexes with interesting electrical conductivity properties and even exhibiting superconductivity are expected to be obtainable by the systematic chemical modification of extended tetrathiafulvalenes (see Figure for one example). The synthesis and cyclic voltammetric characterization of such extended donors are reviewed in detail. magnified image

Dimensionality and Electrical Properties in Organic Synthetic Metals—Current Results through Selected Recent Examples

“…As all these series have been widely reviewed in different articles (24,34,42,43,(52)(53)(54), we only briefly mention here some recent encouraging results obtained with these types of donors.…”

“…This extension was carried out by inserting a conjugated spacer between either two half-TTF (1,3-dithiole cycle) or two TTF entities. Various families of compounds such as (a) vinylogues of TTF derivatives (34)(35)(36)(37)(38)(39)(40), (b) bis-fused TTF (41,42), (c) benzo-fused TTF (43,44), (d) conjugated bis-TTF (45)(46)(47)(48), and (e) directly linked bis-TTF (45-51) were prepared (Scheme 2), and their salts were studied.…”

Synthesis and Electroconductive Properties of Radical Salts Derived from Tetrathiafulvalene Dimers

“…Derivatives (9)(10)(11) In a manner similar to the synthesis of 8, 4-trimethylstannyltetrathiafulvalene derivatives 9, 10, and 11 were prepared from 4,5-bis(methylthio)tetrathiafulvalene (BMT-TTF), 4,5-ethylenedithiotetrathiafulvalene (EDT-TTF), and 4,5-ethylenedioxytetrathiafulvalene (EDO-TTF) in 48%, 55%, and 29% yields, respectively. 9: orange oil, 1 In a manner similar to the synthesis of 2 with Pd(OAc) 2 , bi-TTFs (1, 3, and 4) were synthesized by the reaction of the corresponding trimethyltin-TTF derivatives (8, 10, and 11) with Pd(OAc) 2 To a solution of TTF (207 mg, 1.01 mmol) in THF (5 mL) was added dropwise over 7 min a hexane solution of n-BuLi (1.53 M, 0.7 mL, 1.07 mmol) at -781C under argon atmosphere, and the mixture was stirred at the same temperature for 1 h. A solution of zinc chloride (163 mg, 1.20 mmol) in THF (3 ml) was added dropwise at -781C, and the mixture was stirred at the same temperature for 1 h. The mixture was allowed to warm to À101C, and then PdCl 2 (PPh 3 ) 2 (352 mg, 0.501 mmol) was added to the mixture.…”

“…One important concept to realize high electric conductivity is the enhancement of the dimensionality, which can be attained by use of dichalcogen-capped TTF or by the extended p-conjugation of the TTF framework (8)(9)(10)(11). Thus, a variety of dimeric TTF derivatives have been synthesized in which the two TTF groups are linked by sbonds, single chalcogen atoms, conjugated p-systems, or alkyl chains (8)(9)(10). Among them, bi-TTF 1 is a feasible candidate for constructing organic metals with high dimensionality based on a p-expanded donor.…”

Spin-spin coupling between the two unpaired electrons in cross-conjugated tetrathiafulvalene dication radicals

“…New donors based on the parent TTF moiety have been extensively pursued for molecular organic conductors and ferromagnets, 3 and oligomeric TTFs have been also developed for increased dimensionality of the conducting process or magnetic interaction. 4 Recent modifications of TTF have placed emphasis on the preparation of dimeric TTFs as new electron donors. 5 In addition, theoretical calculations on TTF dimers or oligomers have shed light on the spin-spin interactions between the unpaired electrons in the dication of the TTF dimers, especially the parallel spin ground state in some cases.…”