Bis -TTF

From alkylthio-derivatives of bi-TTF tetraalkylthio-bi-TTF can be obtained using the phosphite-mediated cross-coupling method (strategy S2). Depending on the solvent, an intermediate molecule is obtained whose homocoupling yields the tetraalkylthio-tri-TTF (see Fig. 2.14). 

Raman and near-visible IR spectroscopy has been used to characterize the radical cation of the bis-TTF 4 <1997PCB3665, 1997SM(86)1999>. FTIR has been used to confirm ab initio calculations for the radical cation of benzodithiophene 23 and benzodifuran 24. The bisthiophene was found to adsorb at lower wavelengths than the bisfuran <2000JEC24>. 

The great diversity of systems in this chapter makes a comparison of synthetic approaches difficult and most of the best synthetic approaches have counterparts in the syntheses of simpler heterocycles. Since the area was last reviewed <1996CHEC-II(7)841>, established methods have continued to be of synthetic utilit r, in particular, the photocycliza-tion chemistry of l,2-bis(heteroaryl)ethene systems and the chemistry of bis-TTFs have been further explored. The focus, however, of these research efforts has tended to concentrate on the applications of these materials in electronic devices with less emphasis on novel synthetic approaches. A noticeable trend has been the increasing use of metal-mediated chemistry, in particular, chemistry involving transition metals. The diverse range of metals employed and the number of tricyclic systems synthesized admirably demonstrates the importance of this area. 

A comprehensive review on oligo-TTF has been published [184] covering electrochemical aspects especially of bis-TTF connected through one or two links. More than 100 oligomers are presented. 

The structures of the black crystalline benzene solvate C6o-4C6H6, the black charge-transfer complex with bis(ethylenedithio)tetrathiafulvene, [C6o(BEDT-TTF)2], and the black ferrocene adduct [C6o Fe(Cp)2)2] (Fig. 8.7b) ) have also been solved and all feature the packing of Cso clusters. 

BEDT-TTF Bis(ethylenedithio)tetrathiafulvalene CCDC Cambridge Crystallographic Data Centre... 

Bi-5,6-dihydro-1,3-dithiolo[4,5-b][1,4]-dithiinylidene (BEDT-TTF). J. Larsen and C. Lenoir, Department of General and Organic Chemistry, H. C. Orsted Institute, University of Copenhagen,... 

The synthesis of the bis-l,3-dithiolium radical cation (TTF+) in 1970 [1] enabled dramatic growth in the field of molecular conductors in the decades thereafter. TTF and several of its homologues are depicted in Scheme 1. The field of low dimensional molecular metals was further motivated by the discovery of the TTF-TCNQ charge-transfer complex in 1973 [2, 3]. Seven years later, superconductivity was induced in the cation-radical salt, (TMTSF)2PF6, upon application of 12 kbar pressure [4]. Shortly thereafter, superconductivity below 1.4 K was observed at ambient pressure in the perchlorate analog [5]. 

The l,l -diferrocenyl-VT electron donor molecule is structurally similar to diferrocenyltetrathiafulvalene but with the TTF moiety replaced by bis(vinylene-dithio)tetrathiafulvalene (VT) [76]. It has currently not been possible to separate the cis- and trans-isomers. The 1 1 polyiodide complex of l,l -diferrocenyl-VT was obtained through reaction with iodine. EPR and Mossbauer spectra indicate that in this charge transfer salt the VT moiety is oxidized while the ferrocene... 

Over the past decade a number of new covalently bonded TTF/ferrocene adducts have been reported [77, 78]. The crystal structure of the l,l -bis(l,3-dithiole-2-ylidine)-substituted ferrocene derivative has been published [77]. In this complex, ferrocene has essentially been incorporated as a molecular spacer between the two l,3-dithole-2-ylidene rings forming a stretched TTF molecule. This adduct, and its methyl-substituted derivative, have been combined with TCNQ to form charge-transfer complexes with room temperature powder conductivities of 0.2 S cm-1. Similar diferrocenyl complexes have been prepared with bis (dithiolene) metal complexes [79, 80]. 

As illustrated in Scheme 6, the TTF core has been functionalized with diphenylphosphino moieties to form derivatives such as 3,4-dimethyl-3, 4 -bis (diphenylphosphino)tetrathiafulvalene [o-Me2TTF(PPh2)21 [88] and tetrakis... 

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