Extended TTF system

As is shown in Table 14.1, some other materials were synthesised and subjected to conducting LB film-forming processes. For example, the LB film of the extended TTF system shown in Figure 14.22(a) was... 

This chapter deals with the synthesis, reactivity, and characterization of five-membered heterocycles containing two ring sulfur atoms (1,3-dithiole derivatives) and is a review of the literature in the period 1995-2006. Previous reviews covered the literature till 1982 (CHEC(1984)) <1984CHEC(6)813> and 1995 (CHEC-II(1996)) <1996CHEC-11(3)607>. Among 1,3-dithiole compounds, 1,3-dithiolylium ions 1, mesoionic l,3-dithiol-4-ones 2, mesoionic 1,3-dithiole-4-thiones 3, 1,3-dithioles 4, 1,3-dithiolanes 5, and the tetrathiafulv alene (TTF) system 6 as a special class of compounds are discussed. 7l-Extended tetrathiafulvalenes (7t-exTTFs) containing more than one conjugated multiple bond between two 1,3-dithiole moieties are also discussed, in conjunction with 6. 

In this section, the reactivity of carbon- and heteroatom-containing substituents attached directly or indirectly to the heterocyclic ring of 1,3-dithiole derivatives is discussed. Here, chemical manipulations on these systems exclude ring carbon and sulfur atoms, which are the subject of Section 4.12.6. Special 1,3-dithioles called Jt-extended TTFs, containing two or more 1,3-dithiole moieties linked together via =C-(C=C) -C= or similar conjugated spacers, are discussed with typical TTFs in Section 4.12.11, although formally they constitute an example of functionalization of the 1,3-dithiole by 2rt-extended substituents, terminated by another 1,3-dithiole moiety. 

There has also been continuing interest in extended TTF analogues and examples of this type include 76 <01TL4191>, the azulene systems 77 <01H(54)377>, redox-active dendralenes such as 78 <00CEJ1955> and the heterocycle linked compounds 79 and 80 <01ZN(B)297>, 81 <01CL514> and 82 <01JAP48881>. 

Quite recently, fused TTF analogs having one or two [5]radialene unit(s) 40—42 have also been prepared (Figure 8.18), because the extended TTF moieties are of interest as multi-redox systems, components for molecular conductors, positive electrode materials for rechargeable batteries, and so on [48]. 

One-dimensional stacking of the molecules may provide a framework for possible band structure formation. In this case, repeat units should preferably have an overall planar geometry. This concept can be extended to two-dimensional (2D) structural arrangements where interactions between the molecules are found along two directions as in cation-radical salts derived from TTF-like molecules such as BEDT-TTF (BEDT-TTF = C10H8S8, bis(ethylenedithio)-tetrathiafulvalene) (13), or even to three-dimensional (3D) systems such as the doped A Ceo fullerides (47). 

The only significant difference in the length of the formally double C-3-C-4 bond of the monopyrrolo-TTFs 79 and 88 (1.348 A for 79 and 1.30 A for 88) indicated a more extended rt-electron system in the former compound <2000JOC5794>. 

The role of interchain coupling. Renormalization group methods earlier applied to ID systems have been extended to treat two or more interacting chains, with applications to the 4k problem. Extensions have been given of the Bak-Emory theory of the 38°, 49° and 54°K transitions in TTF-TCNQ in which Coulomb interactions between CDW s on different chains play an important role. Another question is how much 3D effects reduce fluctuations above Tc expected for ID systems. 

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