Structural and transport properties of neutral radical crystals of Co^III(tmp)(CN)₂(tmp = 5,10,15,20-tetramethylporphyrinato) and the CN-bridged polymer [Co^III(tmp)(CN)]_n

Abstract

An axially ligated Co(tmp) (tmp = 5,10,15,20-tetramethylporphyrinato) anion, [Co(tmp)(CN)], has been prepared and subjected to electrochemical oxidation to obtain the open shell tmp π-ligand. With acetone as the solvent, solvent-free neutral radical crystals of Co(tmp)(CN) are obtained, whereas solvent-inclusive crystals of Co(tmp)(CN)·2CHCN are obtained with CHCN as the solvent. In both crystals, the open shell tmp ring deforms into a ruffled form, which makes the π-π interactions in the crystal weak. Thus, the electrical conductivity is low, and the crystals behave as semiconductors with a room temperature resistivity of 10 Ω cm and an activation energy of about 0.3 eV. When the solvent is acetone, non-oxidized crystals of the CN-bridged polymer {[Co(tmp)(CN)](acetone)} are obtained as a byproduct. The closed shell tmp ring deforms into a ruffled form, and there π-π interactions in the crystal are negligible. The room temperature resistivity is rather high at about 10 Ω cm.