[Copper(II)-aryltetraazannulene]Ix complexes as conductive materials. Solid state synthesis and characterization

Cu(dibenzo[b,i][1,4,8,11]tetraaza[14]annulene), Cu(dbTAA), Cu(dinaphtho- [b,il[1,4,8,11]tetraaza[14]annulene), Cu(dnTAA), Cu(diphenanthro[b,i][1,4,8,11]tetraaza [14]annulene) and Cu(dpTAA) complexes have been used for synthesizing new conductive materials. Chemical oxidation of the three compounds in acetone slurries by variable amounts of iodine yielded microcrystalline conductive powders with a wide range of stoichiometries. Thermal stability of the oxidized materials was investigated by TGA and DTGA techniques showing a relationship between solid phase stability and iodine content and, together with IR data, suggests the presence of a single phase. Raman spectra show strong scatterings attributable to I3− (107 cm−1) and (160 cm−1) I5− polyiodides, the latter occurs only in highly iodinated complexes (I/Cu ratio larger than three) and the I2 presence can be excluded. Electrical conductivity measurements of powder samples of the oxidized compounds exhibit some dependence on the iodine content in the I/Cu ratio range 0–0.9. The temperature response of the conductivity of the oxidized compounds, in the range 70–220 K, is interpretable in terms of an activated formation of carriers. ESR spectra, static magnetic susceptibility and IR data as a function of the I/Cu ratio suggest that the oxidative process involves not only the copper unpaired electron, but also electrons associated with delocalized ligand orbitals on the macrocycle. Large enhancement of the conductivity is shown by Cu(dpTAA)I0.2 (1.5 S cm−1) and the temperature dependence of conductivity shows metallic behaviour starting from 200 K.