DT-TTF

There is a very short list of organic semiconductors with reported thin-film field-effect mobilities greater than 1 cm2 V-1 s h These include pentacene, sexithio-phene [5a], and anthradithiophene [17]. If we extend this list to include single crystal and n-type materials, we can add perylene [18], rubrene [19], copper phtha-locyanine (CuPc) [20], tetracyanoquinodimethane (TCNQ) [21], and dithiophene-tetrathiofulvalene (DT-TTF) [22] - still a short list. 

Like the dmit complexes, the mnt complexes are also promising candidates for the synthesis of spin-ladder systems. As previously discussed (Section II.B.l.b), metal-like D-A conductors have been obtained when associating M(mnt)2 and Per (159). Spin-ladder D-A systems have been obtained when associating M(mnt)2 and the dithiopheno-tetrathiafulvalene (DT-TTF = C10H4S6) donor (Scheme 15). 

As expected for a (DT-TTF)+1/2 cation-radical, thermopower measurements indicate a hole transport for (DT-TTF)2[Au(mnt)2], which behaves like a semiconductor with a slight change in the conductivity regime 220 K. Diffuse X-ray scattering studies show that the donors dimerize along the b stacking direction, two DT-TTF molecules sharing one electron. Since Au(mnt)2 is... 

Figure 11. Projection of the structure of (DT-TTF)2[M(mnt)2] onto the be plane. [Adapted from the data available in (307).]...

Although isostructural to the Au complex, the Ni and Pt salts do not form spin-ladder systems. This may be due to slight differences in the transfer integrals within the DT-TTF stacks and also to the paramagnetism of [M(mnt)2] (M = Ni, Pt) that may interact with the DT-TTF system. Related Co and Fe compounds have also been reported (311), but they are just simple ionic salts as shown by their 1 1 stoichiometry (instead of the 2 1 stoichiometry for the Au, Ni and Pt compounds). Very recently, Ribera et al. (307) published an excellent and detailed report on this family of compounds. 

In Section III, we also discussed the spin-ladder behavior of dithiolene complex-based compounds, namely, (p-EPYNN) Ni(dmit)2], (DT-TTF)2-[Au(mnt)2], and [Cp2M(dmid)](TCNQF4). All of these compounds display semiconducting behavior and no interplay of electrical and magnetic properties was reported. 

---