Tetrathiafulvalenes dications

The incorporation of tetrathiafulvalene (TTF) into dendrimers presents a fascinating prospect for the following reasons (1) oxidation of TTF to the cation radical and dication species occurs sequentially and reversibly at very accessible potentials (for unsubstituted TTF, = +0.34 and eY = +0.78 V, vs. Ag/AgCl) (2) the oxidation potentials can be finely tuned by the attachment of appropriate substi-... 

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... 

Table 5 Half-Wave Potentials for the Oxidation of Some Tetrathiafulvalenes and Related Compounds to the Corresponding Cation Radicals and Dications ... 

Similarly to tetrathioethylenes and tetrathiafulvalenes, 1,4-dithiin (LV) and its benzoder-ivatives (LVI and LVII) are electron-rich compounds that can be easily oxidized to their corresponding cation radicals and dications. There are several reviews [2, 3, 186, 187] on the chemistry of the radical cations of dibenzo-1,4-dithiin (LVH) and related compounds. 

Fig. 20. When the tetrathiafulvalene (TTF)-containing thread 16 is mixed in acetonitrile solution with cyclophane CBPQT4+, a pseudorotaxane is formed. This complex can be dissociated in one of two ways - reduction of the cyclophane to its diradical dication, or oxidation of the TTF portion of the thread 16 to its radical cation. Both processes are reversible, by oxidation of the cyclophane and reduction of 16, respectively...

They are formed by (a) a desymmetrized electron acceptor ring containing two different units, namely a 4,4 -bipyridinium dication (BPY " and a neutral naphthalene diimide (NDI) or pyromellitic diimide (PMI) moiety, and (b) an electron donor ring that can be symmetric for the presenee of two identical dioxybenzene (DOB) or dioxynaphthalene (DON) units, or desymmetrized by the presence of two different donors, i.e. a tetrathiafulvalene (TTF) and a DON moiety. 

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