Synthesis, isolation, and structural characterization of the C_4h isomer of metal(1,2-naphthalocyanine) and its one-dimensional conductor of the axially substituted species

The C_4h isomer of the 1,2-Nc (1,2-naphthalocyaninato) ligand has been efficiently isolated as a hydrated magnesium complex by the fractional crystallization from the benzene/acetone solution after treating the crude mixture of the four isomers (C_4h, C_s, C_2v, D_2h) with benzene. The C_4h symmetry has been confirmed by X-ray structure analysis. The central metal ion has been demetalated and subsequently converted to the Li₂ complex followed by conversion to the cobalt(II) complex. Electrochemical oxidation of the Co^III(1,2- Nc)(CN)₂ anion prepared from the cobalt(II) complex with TPP (tetraphenylphosphonium) has yielded a partially oxidized salt, TPP[Co ^III(1,2-Nc-C_4h)(CN)₂]₂. The crystal comprises slipped stacked Co^III(1,2-Nc-C_4h)(CN) ₂ one-dimensional chains and one-dimensional arrays of TPPs. The conductivity at room temperature is 0.1 S cm^-1, and the temperature dependence is semiconducting with a small activation energy of about 0.05 eV. The positive temperature-independent value of about 60 μV deg^-1 observed in the thermoelectric power measurements suggests that the salt is in the correlated hopping regime.