DMe-DCNQI

If we now incorporate functional groups in the CeHe-based molecules we will have important molecules such as CA, DMe-DCNQI, TCNQ, TMPD, TNAP and ITT, but the really big jump is encountered when pentagons are allowed to be included. The possibilities to build new molecules become even more numerous than with only CeHe pieces, although we already had an immense number... 

One of the most investigated salts based on this acceptor molecule is (DMe-DCNQI)2Cu, where DMe is dimethyl (=( 113)2). This compound is especially interesting because a metal-insulator transition, sometimes even with a reentrance to metallic behavior, can be induced either by pressure or by the substitution of hydrogen with deuterium in the organic complex... 

The crystal structure has tetragonal symmetry with the space group /4i/a. The planar DMe-DCNQI anions are stacked in ID columns along the tetragonal c axis. The LUMO consists of orbitals and forms a wide ID conduction band which is partly filled with electrons donated by the cations. The Cu ions are in a mixed valence state, namely [Cu ] [Cu" "] = 1 2... 

Table 4.3. Experimental and calculated values of dHvA frequencies and effective cyclotron masses in undeuterated (DMe-DCNQI)2Cu. For the e orbits no effective masses have been calculated. From [388]...

Fig. 4.45. (a) Schematic projection of the 3D FS of (DMe--DCNQI)2Cu in the repeated zone scheme, (b) Cut of the FS through the ab plane. The proposed dHvA orbits are shown by the solid lines. From [388]... 

Some Cu NMR studies have been carried out for the organic conductors (DMe-DCNQIjaCu, (DMeO-DCNQI)2Cu, (DBr-DCNQI)2Cu and partiaUy deuterated (DMe-DCNQI-d2[l, l 0])2Cu. The results show that the metallic and insulating states each possess similar electronic and magnetic properties. A systematic measurement of (l/Ti) for Cu failed to identify any specific effect of d-electron correlations near the metal-insulator (Cu-I) boundary. 

Various different applications of the conductivity properties of the DCNQI salts have been suggested [13]. The very rapid change in microwave reflectivity with light-induced phase transformations in partially-deuterated [2,5-DMe-DCNQI]2 Cu alloys can be used for fast microwave switching [20]. Thin films of special DCNQI salts can be used as sensors for paramagnetic gases such as O2 and NO [21]. AppH-cations in electrophotography have also been discussed. 

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