Hetero-TCNQ complexes

Table 4.3. Physical properties of hetero-TCNQ complexes... 

Volume 1 contains 15 chapters on the recent developments in charge-transfer salts, fullerenes, photoconductors and molecular conductors. The topics covered include electron acceptor molecules, photo-induced intermolecular electron transfer systems, perylene based conductors, tetrachalcogenafulvalenes, metal 1,2-dichaIcogenoIenes and their conductive salts, conductive hetero-TCNQs (tetracyano-p-quinodi-methane derivatives), molecular metals and superconductors based on transition metal complexes. 

Table 4.2. Abbreviations and half-wave oxidation potentials of various electron donors that form complexes with hetero-TCNQs...

As mentioned earlier, 1 shows lower reduction potentials than TCNQ, reflecting the lower aromaticity of thiophene than benzene. In cyclic voltammetry, the first half-wave reduction potentials of 27 and 30 are further lower than that of 1 (Table 4.1). However, gaps between the first and second reduction waves become smaller with separation of the two dicyanomethylene groups as expected, demonstrating effective reduction of on-site coulombic repulsion in the dianionic states. In particular, the second wave of 30 coalesces into the first one as a result of minimization of on-site coulombic repulsion. The conjugated hetero-TCNQs 27 and 30 like 1 form non-ionic complexes with TTF, but interestingly their electrical conductivities are... 

---