Highly-conducting neutral copper complexes substituted with two tetrathiafulvalenyldithiolato groups

The neutral bis(dialkylthiotetrathiafulvalenyldithiolato)copper complexes, Cu(R2C6S8)2 (R=Me 1a, Et 1b, R2=–CH2CH2– 1c) were synthesized by the reaction of bis(tetramethylammonium or tetraethylammonium) bis(dialkylthiotetrathiafulvalenyldithiolato)zincate complexes with CuCl2 in DMF, followed by oxidation with iodine. The room-temperature electrical conductivities were 7.8×10–2 , 5.0×10–4 and 3.7 S cm–1 for compressed pellets of 1a, 1b and 1c, respectively. Magnetic susceptibility measurements showed that the remaining spin on the copper atoms is very small for these complexes as a result of large intramolecular electron transfer from CuII atom to the tetrathiafulvalenyl radical cation ligands.