Novel phthalocyanine‐based conductors: tunable Π–Π stacking structure through the steric and chemical interactions of axial ligands

Various electrically conducting neutral radical and partially oxidized salt crystals can be obtained by electrochemical oxidation of dicyano(phthalocyaninato)cobalt(III) anion, [Co(Pc)(CN)2]−. In most of the neutral radical crystals, crystal solvents are incorporated in the lattice, and the dimensionality of the π–π interaction can be tuned by selecting the solvent. When the neutral radical crystallizes without crystal solvents, the π–π interaction becomes much less efficient. The electrical conductivity of the solvent-inclusive crystals is high, 10−2–1 S cm−1 at room temperature, while that of the solvent-free crystal is much lower, ∼10−4 S cm−1. The partially oxidized salt crystals have been obtained when the cation is K+, TPP+ or (PXX2)+ (TPP+≡tetraphenylphosphonium; PXX≡peri-xanthenoxanthene). In these crystals the Pc π-ligand is commonly oxidized by 0.5e, and they show high conductivity up to 2 × 102 S cm−1 at room temperature. The dimensionality of the π–π interactions is varied by the shape of the cationic part.