Tetrathiafulvalene moieties

The crystal structure of pentathiepino [6,7- indole has been determined <1994TL5279>. X-Ray crystal structure analysis revealed that 4,5-ethylenedithio-4,5-pentathiotetrathiofulvalene <1999AM758> moiety has a bent structure resembling the molecular structure of neutral bis(ethylenedithio)tetrathiafulvalene and that the pentathio group adopts a chair-formed conformation. The intradimer interplane distance is 3.35 A, which is much shorter than the interdimer one (4.45 A). In a molecule, there are many intermolecular S-S contacts shorter than the sum of the van der Waals radii (3.7 A), and a two-dimensional network of sulfur atoms was developed between the pentathio groups and tetrathiafulvalene moieties. Furthermore, chlorobenzene molecules are beside the anion and occupy the void space as the interstitial solvent. They are also located on the mirror plane and are disordered at two positions with inversion symmetry because of the cavity structure of the void space. 

Classification of macrocyclic compounds containing tetrathiafulvalene moieties, synthetic methods, the latest advances in research on electrochemical properties and applications to molecular recognition and development trends in research on such macrocyclic compounds were outlined and reviewed <2007MI1220>. 

Other electrically conducting systems like bimetallic complexes, thioxolato polymers, polymers with tetrathiafulvalene moieties or poly(phosphazane)s are reviewed in [120]. 

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... 

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... 

With the objective to enable long-lived charge-separated CgQ-complexes (also Section 4.2) TTF and extended TTF were bound via [3-1-2] cycloaddition with different spacer-lengths (Rj) (Figure 4.12) [215, 252-257]. In these C q-TTF dyads as well as in a bis-tetrathiafulvalene-Cgo triad no significant interaction between the TTF units and the CgQ-moiety in the ground state could be observed. 

An unusual six-electron cycloaddition could be observed in the reaction of CgQpjg with tetrathiafulvalene (TTF) [70], TTF is not added to one of the free double bonds but replaces two of the fluorine atoms in a way that leaves the CgQpjg moiety, whose structure is described above (Figure 9.1). Under loss of F2 the product Cjq Fi6(TTF) is formed (Figure 9.7). 

Upon the first reduction, the voltammetric wave shifts by 20-30 mV, presumably due to donor-acceptor interactions resulting from the naphthalene and cyclophane moieties.39 The second reduction remains relatively unaffected, indicating that the complex disassembles prior to the second reduction of the cyclophane. Alternatively, the complex can disassemble through competitive binding interactions with a tetrathiafulvalene derivative. Thus, Cooke and coworkers demonstrate that self-assembly at exo-active surfaces can be reversibly controlled via an external electrochemical stimulus or competitive binding interactions. 

The [2]rotaxanes, which contain tetrathiafulvalene (TTF) and 1,5-dioxynaphtha-lene (DNP) as the two recognition stations and cyclobis(paraquat-p-phenylene) (CBPQT4 + ) as the cyclic moiety, have been comprehensively investigated by Stoddart and coworkers.68 We have recently reported two new TTF-DNP-CBPQT4+ [2]rotaxanes 62 and 63. In these two [2]rotaxanes, the TTF moiety is the 4,4 (5 )-dialkylthiotetrathiafulvalene that is rather easily accessible based on the synthetic procedure developed by us previously,69 and two different spacers are used the cyclohexyl and alkyl chains. Two stopper units are the G2-dendritic moieties. 

The combination of a phthalocyanine ring with crown ether moieties and redox-active tetrathiafulvalenes gave compound 117 (Scheme 64) and was described by Zou as a good candidate for a redox-active Na+ sensor [133]. 

Despite some small spectral differences, the similarities have been sufficient to confirm the slow step in the electrochemistry of immobilized cobalt porphyrin mediators (113) and to identify the intermediates involved in a tetrathiafulvalene polymer coated electrode (7). A polyxylylviologen -polystyrenesulfonate co-polymer coated electrode, on the other hand, showed no changes in the position of the peaks in the absorption spectra upon immobilization (111). Presumably this indicated an absence of interactions between neighboring viologen moieties. Similar spectral results have been obtained using photoacoustic spectroscopy (PAS). Heptyl viologen adsorbed on Pt exhibited an unshifted spectrum which correlated with the electrochemical results (115). 

There is a long standing interest in the chemistry and the properties of cyclic compounds containing sulfur atom in modern material chemistry due to their redox chemistry. In particular, the focus has been on dithiole derivatives, e.g., dithiafulvenes and tetrathiafulvalenes, since the finding of metallic conductivity and low temperature superconductivity in radical cation salts. The quite low oxidation potentials of 1,4-dithiin compounds have been reported, recently [109]. On the other hand, thioketene dimers (2,4-bis(alkyli-dene)-l,3-dithietane) have been known for more than 100 years and synthesized by various methods [110-115]. The structure of these dimer compounds is similar to that of the redox-active sulfur compounds therefore, the potential electronic property of the thioketene dimer moiety is considerably attractive with the aim of application to a new and better -donor. 

Figure 6.40 Paraquat, the electron deficient blue box developed by Stoddart and co-workers and a later derivative. Electron deficient aromatic rings are coloured blue, red is used for electron rich rings, neutral hydrocarbons are coloured black while green is used for other moieties such as tetrathiafulvalene.

Double-layered tetrathiafulvalenes have been prepared but with different face-to-face orientations. The coupling of 12 with triethylphosphine in toluene under reflux gave (26 %) 13, in which the TTF planes are slightly bent into a boat shape and overlapped with each other [95CL523]. Whereas, the related dimeric structure 14, where the two TTF moieties possess a cross-orientation, has recently been reported [95CL579,95TL5045]. 

Several organofullerene donor-acceptor molecular material hybrid systems have been synthesized via 1,3-dipolar cycloaddition reactions of azomethine ylides, via Bingel cyclopropanation and methanofullerene formation intermediates as well as via cycloaddition reactions, that have already been discussed in previous sections. The majority of such hybrid systems possess always as acceptor unit the fullerene core and as donor moieties porphyrins, tetrathiafulvalenes, ferrocenes, quinones, or electron-rich aromatic compounds that absorb visible light [190-193]. The most active research topic in this particularly technological field relies (i) on the arrangement of several redox-active building blocks in... 

For further information on synthesis, properties, and applications of pyrro-lidinofullerenes, the chiral representatives of which were generally prepared and used as racemates, we refer to a recent review by Prato and Maggini.214 Fields in which many fullerene-fused pyrrolidines have been studied are biological and medicinal chemistry351 and, above all, advanced materials science.352,353 In the latter context, dyads and triads used for photoinduced charge separation between a fullerene acceptor moiety and electron donors like porphyrins, tetrathiafulvalenes, ferrocenes, or polyenes, are worth particular mentioning.354-356... 

As already pointed out in the case of rotaxanes, mechanical movements can also be induced in catenanes by chemical, electrochemical, and photochemical stimulation. Catenanes 164+ and 174+ (Fig. 19) are examples of systems in which the conformational motion can be controlled electrochemically [82, 83], They are made of a symmetric electron acceptor, tetracationic cyclophane, and a desymmetrized ring comprising two different electron donor units, namely a tetrathiafulvalene (TTF) and a dimethoxybenzene (DOB) (I64 1) or a dimethoxynaphthalene (DON) (174+) unit. Because the TTF moiety is a better electron donor than the dioxyarene units, as witnessed by the potentials values for their oxidation, the thermodynamically stable conformation of these catenanes is that in which the symmetric cyclophane encircles the TTF unit of the desymmetrized macrocycle (Fig. 19a, state 0). 

During stepwise oxidation, each of the tetrathiafulvalene (TTF) or 4,5-dimethyltetrathiofulvalene (o-DMTTF) moieties in 90-92 donates two electrons so that exhaustive oxidation at potentials below IV (vs. SCE) leads to dications 90 + the tetracations 91" + and hexacations 92 +. In the initially formed radical cations... 

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