Fractional oxidation state compounds FOSC

A large number of C [M(dmit)2] complexes (n = 2, 1, 0) have been prepared. " The dianion salts [R4N]2[M(dmit)2] can be obtained by treating a solution of Na2dmit in methanol with the appropriate M metal salt and the appropriate tetraalkylammonium bromide (Figure 4.18). The corresponding monoanionic salt [R4N][M(dmit)2] is obtained from the dianionic salt by iodine oxidation. Further oxidation may lead to the neutral complex or to fractional oxidation state compounds (FOSCs) or donor-acceptor (DA) compounds. These oxidation steps are described in Section 4.3.2. 

Figure 4.18 Synthesis of the [dmit] ligand, its storable derivatives and [M(dmit)2] compounds. (FOSC = fractional oxidation state compound DA = donor-acceptor compound)...

Metal bis-dithiolene complexes exhibiting conducting or superconducting properties can be neutral or in a fractional oxidation state. In FOSCs, the associated cation is of the closed-shell type, while in DA compounds, the metal bis-dithiolene is an acceptor and the donor is an open-shell cation. As already mentioned in Section 4.2.2.3, the most encountered... 

In the case of DA compounds, both donor and acceptor molecules may undergo oxidation towards fractional oxidation states. In general, their half wave potentials are similar and formation of the DA compound may compete with crystal growth of FOSC phases. This feature was illustrated in the case of TTF[Ni(dmit)2]2. Single crystals of this phase were electrocrystallized using TTF and TBA[Ni(dmit)2]. The cyclic voltammogram of each compound shows that [Ni(dmit)2] is oxidized at a potential 120 mV lower than that of TTF. However, addition of TTF to a solution of (Bun)4[Ni(dmit)2] inhibits the formation of the (Bun)4 o.29[Nl(dmit)2] FOSC phase in favor of the TTF[Ni(dmit)2]2 one.76... 

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